From 6857767b8600a361188f75e62c086ed7d7c06d7c Mon Sep 17 00:00:00 2001 From: Ryan Lortie Date: Sat, 30 Jan 2010 12:32:09 -0500 Subject: [PATCH] move threads docs to .c --- docs/reference/glib/tmpl/.gitignore | 1 + docs/reference/glib/tmpl/threads.sgml | 1801 ------------------------- glib/gthread.c | 1492 +++++++++++++++++++- 3 files changed, 1475 insertions(+), 1819 deletions(-) delete mode 100644 docs/reference/glib/tmpl/threads.sgml diff --git a/docs/reference/glib/tmpl/.gitignore b/docs/reference/glib/tmpl/.gitignore index 2d2122ddb..9cd641561 100644 --- a/docs/reference/glib/tmpl/.gitignore +++ b/docs/reference/glib/tmpl/.gitignore @@ -5,3 +5,4 @@ gvarianttype.sgml hash_tables.sgml option.sgml random_numbers.sgml +threads.sgml diff --git a/docs/reference/glib/tmpl/threads.sgml b/docs/reference/glib/tmpl/threads.sgml deleted file mode 100644 index feb939998..000000000 --- a/docs/reference/glib/tmpl/threads.sgml +++ /dev/null @@ -1,1801 +0,0 @@ - -Threads - - - -thread abstraction; including threads, different mutexes, conditions -and thread private data - - - - -Threads act almost like processes, but unlike processes all threads of -one process share the same memory. This is good, as it provides easy -communication between the involved threads via this shared memory, and -it is bad, because strange things (so called "Heisenbugs") might -happen if the program is not carefully designed. In particular, due to -the concurrent nature of threads, no assumptions on the order of -execution of code running in different threads can be made, unless -order is explicitly forced by the programmer through synchronization -primitives. - - - -The aim of the thread related functions in GLib is to provide a -portable means for writing multi-threaded software. There are -primitives for mutexes to protect the access to portions of memory -(#GMutex, #GStaticMutex, #G_LOCK_DEFINE, #GStaticRecMutex and -#GStaticRWLock). There are primitives for condition variables to allow -synchronization of threads (#GCond). There are primitives -for thread-private data - data that every thread has a private instance of -(#GPrivate, #GStaticPrivate). Last but definitely not least there are -primitives to portably create and manage threads (#GThread). - - - -The threading system is initialized with g_thread_init(), which takes -an optional custom thread implementation or %NULL for the default implementation. -If you want to call g_thread_init() with a non-%NULL argument this must be done -before executing any other GLib functions (except g_mem_set_vtable()). This is a -requirement even if no threads are in fact ever created by the process. - - - -Calling g_thread_init() with a %NULL argument is somewhat more relaxed. You -may call any other glib functions in the main thread before g_thread_init() as -long as g_thread_init() is not called from a glib callback, or with any locks held. -However, many libraries above glib does not support late initialization of -threads, so doing this should be avoided if possible. - - - -Please note that since version 2.24 the GObject initialization -function g_type_init() initializes threads (with a %NULL argument), so -most applications, including those using Gtk+ will run with threads -enabled. If you want a special thread implementation, make sure you -call g_thread_init() before g_type_init() is called. - - - -After calling g_thread_init(), GLib is completely -thread safe (all global data is automatically locked), but individual -data structure instances are not automatically locked for performance -reasons. So, for example you must coordinate accesses to the same -#GHashTable from multiple threads. The two notable exceptions from -this rule are #GMainLoop and #GAsyncQueue, -which are threadsafe and needs no further -application-level locking to be accessed from multiple threads. - - - -To help debugging problems in multithreaded applications, GLib supports -error-checking mutexes that will give you helpful error messages on -common problems. To use error-checking mutexes, define the symbol -#G_ERRORCHECK_MUTEXES when compiling the application. - - - - - - - -#GThreadPool -Thread pools. - - - -#GAsyncQueue -Send asynchronous messages between threads. - - - - - - - - - - - -This macro is defined if GLib was compiled with thread support. This -does not necessarily mean that there is a thread implementation -available, but it does mean that the infrastructure is in place and -that once you provide a thread implementation to g_thread_init(), GLib -will be multi-thread safe. If #G_THREADS_ENABLED is not defined, then -Glib is not, and cannot be, multi-thread safe. - - - - - - - -This macro is defined if POSIX style threads are used. - - - - - - - -This macro is defined if no thread implementation is used. You can, -however, provide one to g_thread_init() to make GLib multi-thread safe. - - - - - - -The error domain of the GLib thread subsystem. - - - - - - -Possible errors of thread related functions. - - -@G_THREAD_ERROR_AGAIN: a thread couldn't be created due to resource -shortage. Try again later. - - - - -This function table is used by g_thread_init() to initialize the -thread system. The functions in the table are directly used by their -g_* prepended counterparts (described in this document). For example, -if you call g_mutex_new() then mutex_new() from the table provided to -g_thread_init() will be called. - - - - -Do not use this struct unless you know what you are doing. - - - -@mutex_new: -@mutex_lock: -@mutex_trylock: -@mutex_unlock: -@mutex_free: -@cond_new: -@cond_signal: -@cond_broadcast: -@cond_wait: -@cond_timed_wait: -@cond_free: -@private_new: -@private_get: -@private_set: -@thread_create: -@thread_yield: -@thread_join: -@thread_exit: -@thread_set_priority: -@thread_self: -@thread_equal: - - - - -If you use GLib from more than one thread, you must initialize -the thread system by calling g_thread_init(). Most of the time you -will only have to call g_thread_init (NULL). - - - -Do not call g_thread_init() with a non-%NULL parameter unless you -really know what you are doing. - - - -g_thread_init() must not be called directly or indirectly as a -callback from GLib. Also no mutexes may be currently locked while -calling g_thread_init(). - - - -g_thread_init() changes the way in which #GTimer measures elapsed time. -As a consequence, timers that are running while g_thread_init() is called -may report unreliable times. - - - -Calling g_thread_init() multiple times is allowed (since version -2.24), but nothing happens except for the first call. If the argument -is non-%NULL on such a call a warning will be printed, but otherwise -the argument is ignored. - - - -If no thread system is available and @vtable is %NULL or if not all -elements of @vtable are non-%NULL, then g_thread_init() will abort. - - - - -To use g_thread_init() in your program, you have to link with the -libraries that the command pkg-config --libs gthread-2.0 -outputs. This is not the case for all the other thread related functions of -GLib. Those can be used without having to link with the thread libraries. - - - -@vtable: a function table of type #GThreadFunctions, that provides the -entry points to the thread system to be used. - - - - -This function returns %TRUE if the thread system is initialized, and -%FALSE if it is not. - - - - -This function is actually a macro. Apart from taking the address of it -you can however use it as if it was a function. - - - -@Returns: %TRUE, if the thread system is initialized. - - - - - - - -@Returns: - - - - -Specifies the type of the @func functions passed to -g_thread_create() or g_thread_create_full(). - - -@data: data passed to the thread. -@Returns: the return value of the thread, which will be returned by -g_thread_join(). - - - - -Specifies the priority of a thread. - - - - -It is not guaranteed that threads with different priorities really -behave accordingly. On some systems (e.g. Linux) there are no thread -priorities. On other systems (e.g. Solaris) there doesn't seem to be -different scheduling for different priorities. All in all try to avoid -being dependent on priorities. - - - -@G_THREAD_PRIORITY_LOW: a priority lower than normal -@G_THREAD_PRIORITY_NORMAL: the default priority -@G_THREAD_PRIORITY_HIGH: a priority higher than normal -@G_THREAD_PRIORITY_URGENT: the highest priority - - - -The #GThread struct represents a running thread. It has three public -read-only members, but the underlying struct is bigger, so you must -not copy this struct. - - - - -Resources for a joinable thread are not fully released until -g_thread_join() is called for that thread. - - - - - - -This function creates a new thread with the default priority. - - - -If @joinable is %TRUE, you can wait for this threads termination -calling g_thread_join(). Otherwise the thread will just disappear when -it terminates. - - - -The new thread executes the function @func with the argument -@data. If the thread was created successfully, it is returned. - - - -@error can be %NULL to ignore errors, or non-%NULL to report errors. The -error is set, if and only if the function returns %NULL. - - -@func: a function to execute in the new thread. -@data: an argument to supply to the new thread. -@joinable: should this thread be joinable? -@error: return location for error. -@Returns: the new #GThread on success. - - - - -This function creates a new thread with the priority @priority. If the -underlying thread implementation supports it, the thread gets a stack -size of @stack_size or the default value for the current platform, if -@stack_size is 0. - - - -If @joinable is %TRUE, you can wait for this threads termination -calling g_thread_join(). Otherwise the thread will just disappear when -it terminates. If @bound is %TRUE, this thread will be scheduled in -the system scope, otherwise the implementation is free to do -scheduling in the process scope. The first variant is more expensive -resource-wise, but generally faster. On some systems (e.g. Linux) all -threads are bound. - - - -The new thread executes the function @func with the argument -@data. If the thread was created successfully, it is returned. - - - -@error can be %NULL to ignore errors, or non-%NULL to report errors. The -error is set, if and only if the function returns %NULL. - - - - -It is not guaranteed that threads with different priorities really -behave accordingly. On some systems (e.g. Linux) there are no thread -priorities. On other systems (e.g. Solaris) there doesn't seem to be -different scheduling for different priorities. All in all try to avoid -being dependent on priorities. Use %G_THREAD_PRIORITY_NORMAL here as a -default. - - - - - -Only use g_thread_create_full() if you really can't use -g_thread_create() instead. g_thread_create() does not take -@stack_size, @bound, and @priority as arguments, as they should only -be used in cases in which it is unavoidable. - - - -@func: a function to execute in the new thread. -@data: an argument to supply to the new thread. -@stack_size: a stack size for the new thread. -@joinable: should this thread be joinable? -@bound: should this thread be bound to a system thread? -@priority: a priority for the thread. -@error: return location for error. -@Returns: the new #GThread on success. - - - - -This functions returns the #GThread corresponding to the calling thread. - - -@Returns: the current thread. - - - - -Waits until @thread finishes, i.e. the function @func, as given -to g_thread_create(), returns or g_thread_exit() is called by -@thread. All resources of @thread including the #GThread struct are -released. @thread must have been created with @joinable=%TRUE in -g_thread_create(). The value returned by @func or given to -g_thread_exit() by @thread is returned by this function. - - -@thread: a #GThread to be waited for. -@Returns: the return value of the thread. - - - - -Changes the priority of @thread to @priority. - - - - -It is not guaranteed that threads with different priorities really -behave accordingly. On some systems (e.g. Linux) there are no thread -priorities. On other systems (e.g. Solaris) there doesn't seem to be -different scheduling for different priorities. All in all try to avoid -being dependent on priorities. - - - -@thread: a #GThread. -@priority: a new priority for @thread. - - - - -Gives way to other threads waiting to be scheduled. - - - -This function is often used as a method to make busy wait less -evil. But in most cases you will encounter, there are better methods -to do that. So in general you shouldn't use this function. - - - - - - -Exits the current thread. If another thread is waiting for that thread -using g_thread_join() and the current thread is joinable, the waiting -thread will be woken up and get @retval as the return value of -g_thread_join(). If the current thread is not joinable, @retval is -ignored. Calling - - - - - -g_thread_exit (retval); - - - - - -is equivalent to calling - - - - - -return retval; - - - - - -in the function @func, as given to g_thread_create(). - - - - -Never call g_thread_exit() from within a thread of a #GThreadPool, as -that will mess up the bookkeeping and lead to funny and unwanted results. - - - -@retval: the return value of this thread. - - - - - - - -@thread_func: -@user_data: - - - - - -The #GMutex struct is an opaque data structure to represent a mutex -(mutual exclusion). It can be used to protect data against shared -access. Take for example the following function: - - -A function which will not work in a threaded environment - - int give_me_next_number () - { - static int current_number = 0; - - /* now do a very complicated calculation to calculate the new number, - this might for example be a random number generator */ - current_number = calc_next_number (current_number); - return current_number; - } - - - - - -It is easy to see that this won't work in a multi-threaded -application. There current_number must be protected against shared -access. A first naive implementation would be: - - - - -The wrong way to write a thread-safe function - - int give_me_next_number () - { - static int current_number = 0; - int ret_val; - static GMutex * mutex = NULL; - - if (!mutex) - mutex = g_mutex_new (); - g_mutex_lock (mutex); - ret_val = current_number = calc_next_number (current_number); - g_mutex_unlock (mutex); - return ret_val; - } - - - - - -This looks like it would work, but there is a race condition while -constructing the mutex and this code cannot work reliable. Please do -not use such constructs in your own programs! One working solution is: - - - - -A correct thread-safe function - - static GMutex *give_me_next_number_mutex = NULL; - - /* this function must be called before any call to give_me_next_number () - it must be called exactly once. */ - void init_give_me_next_number () - { - g_assert (give_me_next_number_mutex == NULL); - give_me_next_number_mutex = g_mutex_new (); - } - - int give_me_next_number () - { - static int current_number = 0; - int ret_val; - - g_mutex_lock (give_me_next_number_mutex); - ret_val = current_number = calc_next_number (current_number); - g_mutex_unlock (give_me_next_number_mutex); - return ret_val; - } - - - - - -#GStaticMutex provides a simpler and safer way of doing this. - - - -If you want to use a mutex, and your code should also work without -calling g_thread_init() first, then you can not use a #GMutex, as -g_mutex_new() requires that the thread system be initialized. Use a -#GStaticMutex instead. - - - -A #GMutex should only be accessed via the following functions. - - - - -All of the g_mutex_* functions are actually macros. -Apart from taking their addresses, you can however use them as if they -were functions. - - - - - - - -Creates a new #GMutex. - - - - -This function will abort if g_thread_init() has not been called yet. - - - -@Returns: a new #GMutex. - - - - - -Locks @mutex. If @mutex is already locked by another thread, the -current thread will block until @mutex is unlocked by the other -thread. - - - -This function can be used even if g_thread_init() has not yet been -called, and, in that case, will do nothing. - - - - -#GMutex is neither guaranteed to be recursive nor to be non-recursive, -i.e. a thread could deadlock while calling g_mutex_lock(), if it -already has locked @mutex. Use #GStaticRecMutex, if you need recursive -mutexes. - - - -@mutex: a #GMutex. - - - - - -Tries to lock @mutex. If @mutex is already locked by another -thread, it immediately returns %FALSE. Otherwise it locks @mutex -and returns %TRUE. - - - -This function can be used even if g_thread_init() has not yet been -called, and, in that case, will immediately return %TRUE. - - - - -#GMutex is neither guaranteed to be recursive nor to be non-recursive, -i.e. the return value of g_mutex_trylock() could be both %FALSE or -%TRUE, if the current thread already has locked @mutex. Use -#GStaticRecMutex, if you need recursive mutexes. - - - -@mutex: a #GMutex. -@Returns: %TRUE, if @mutex could be locked. - - - - - -Unlocks @mutex. If another thread is blocked in a g_mutex_lock() call -for @mutex, it will be woken and can lock @mutex itself. - - - -This function can be used even if g_thread_init() has not yet been -called, and, in that case, will do nothing. - - -@mutex: a #GMutex. - - - - - -Destroys @mutex. - - - - -Calling g_mutex_free() on a locked mutex may result in undefined behaviour. - - - -@mutex: a #GMutex. - - - - - -A #GStaticMutex works like a #GMutex, but it has one significant -advantage. It doesn't need to be created at run-time like a #GMutex, -but can be defined at compile-time. Here is a shorter, easier and -safer version of our give_me_next_number() example: - - - - -Using <structname>GStaticMutex</structname> to simplify thread-safe programming - - int give_me_next_number () - { - static int current_number = 0; - int ret_val; - static GStaticMutex mutex = G_STATIC_MUTEX_INIT; - - g_static_mutex_lock (&mutex); - ret_val = current_number = calc_next_number (current_number); - g_static_mutex_unlock (&mutex); - return ret_val; - } - - - - - -Sometimes you would like to dynamically create a mutex. If you don't -want to require prior calling to g_thread_init(), because your code -should also be usable in non-threaded programs, you are not able to -use g_mutex_new() and thus #GMutex, as that requires a prior call to -g_thread_init(). In theses cases you can also use a #GStaticMutex. It -must be initialized with g_static_mutex_init() before using it and -freed with with g_static_mutex_free() when not needed anymore to free -up any allocated resources. - - - -Even though #GStaticMutex is not opaque, it should only be used with -the following functions, as it is defined differently on different -platforms. - - - -All of the g_static_mutex_* functions apart from -g_static_mutex_get_mutex can also be used even if -g_thread_init() has not yet been called. Then they do nothing, apart -from g_static_mutex_trylock, which does nothing -but returning %TRUE. - - - - -All of the g_static_mutex_* functions are actually -macros. Apart from taking their addresses, you can however use them -as if they were functions. - - - - - - - -A #GStaticMutex must be initialized with this macro, before it can be -used. This macro can used be to initialize a variable, but it cannot -be assigned to a variable. In that case you have to use -g_static_mutex_init(). - - - - - -GStaticMutex my_mutex = G_STATIC_MUTEX_INIT; - - - - - - - - -Initializes @mutex. Alternatively you can initialize it with -#G_STATIC_MUTEX_INIT. - - -@mutex: a #GStaticMutex to be initialized. - - - - -Works like g_mutex_lock(), but for a #GStaticMutex. - - -@mutex: a #GStaticMutex. - - - - - -Works like g_mutex_trylock(), but for a #GStaticMutex. - - -@mutex: a #GStaticMutex. -@Returns: %TRUE, if the #GStaticMutex could be locked. - - - - - -Works like g_mutex_unlock(), but for a #GStaticMutex. - - -@mutex: a #GStaticMutex. - - - - - -For some operations (like g_cond_wait()) you must have a #GMutex -instead of a #GStaticMutex. This function will return the -corresponding #GMutex for @mutex. - - -@mutex: a #GStaticMutex. -@Returns: the #GMutex corresponding to @mutex. - - - - -Releases all resources allocated to @mutex. - - - -You don't have to call this functions for a #GStaticMutex with an -unbounded lifetime, i.e. objects declared 'static', but if you have a -#GStaticMutex as a member of a structure and the structure is freed, -you should also free the #GStaticMutex. - - - - -Calling g_static_mutex_free() on a locked mutex may result in undefined behaviour. - - - -@mutex: a #GStaticMutex to be freed. - - - - - -The %G_LOCK_* macros provide a convenient interface to #GStaticMutex -with the advantage that they will expand to nothing in programs -compiled against a thread-disabled GLib, saving code and memory -there. #G_LOCK_DEFINE defines a lock. It can appear anywhere variable -definitions may appear in programs, i.e. in the first block of a -function or outside of functions. The @name parameter will be mangled -to get the name of the #GStaticMutex. This means that you can use -names of existing variables as the parameter - e.g. the name of the -variable you intent to protect with the lock. Look at our -give_me_next_number() example using the %G_LOCK_* macros: - - - - -Using the %G_LOCK_* convenience macros - -G_LOCK_DEFINE (current_number); - -int give_me_next_number () - { - static int current_number = 0; - int ret_val; - - G_LOCK (current_number); - ret_val = current_number = calc_next_number (current_number); - G_UNLOCK (current_number); - return ret_val; - } - - - - -@name: the name of the lock. - - - - - -This works like #G_LOCK_DEFINE, but it creates a static object. - - -@name: the name of the lock. - - - - - -This declares a lock, that is defined with #G_LOCK_DEFINE in another module. - - -@name: the name of the lock. - - - - - -Works like g_mutex_lock(), but for a lock defined with #G_LOCK_DEFINE. - - -@name: the name of the lock. - - - - - -Works like g_mutex_trylock(), but for a lock defined with #G_LOCK_DEFINE. - - -@name: the name of the lock. -@Returns: %TRUE, if the lock could be locked. - - - - - -Works like g_mutex_unlock(), but for a lock defined with #G_LOCK_DEFINE. - - -@name: the name of the lock. - - - - -A #GStaticRecMutex works like a #GStaticMutex, but it can be locked -multiple times by one thread. If you enter it n times, you have to -unlock it n times again to let other threads lock it. An exception is -the function g_static_rec_mutex_unlock_full(): that allows you to -unlock a #GStaticRecMutex completely returning the depth, (i.e. the -number of times this mutex was locked). The depth can later be used to -restore the state of the #GStaticRecMutex by calling -g_static_rec_mutex_lock_full(). - - - -Even though #GStaticRecMutex is not opaque, it should only be used with -the following functions. - - - -All of the g_static_rec_mutex_* functions can be -used even if g_thread_init() has not been called. Then they do -nothing, apart from g_static_rec_mutex_trylock, -which does nothing but returning %TRUE. - - - - - -A #GStaticRecMutex must be initialized with this macro before it can -be used. This macro can used be to initialize a variable, but it -cannot be assigned to a variable. In that case you have to use -g_static_rec_mutex_init(). - - - - - -GStaticRecMutex my_mutex = G_STATIC_REC_MUTEX_INIT; - - - - - - - - -A #GStaticRecMutex must be initialized with this function before it -can be used. Alternatively you can initialize it with -#G_STATIC_REC_MUTEX_INIT. - - -@mutex: a #GStaticRecMutex to be initialized. - - - - -Locks @mutex. If @mutex is already locked by another thread, the -current thread will block until @mutex is unlocked by the other -thread. If @mutex is already locked by the calling thread, this -functions increases the depth of @mutex and returns immediately. - - -@mutex: a #GStaticRecMutex to lock. - - - - -Tries to lock @mutex. If @mutex is already locked by another thread, -it immediately returns %FALSE. Otherwise it locks @mutex and returns -%TRUE. If @mutex is already locked by the calling thread, this -functions increases the depth of @mutex and immediately returns %TRUE. - - -@mutex: a #GStaticRecMutex to lock. -@Returns: %TRUE, if @mutex could be locked. - - - - -Unlocks @mutex. Another thread will be allowed to lock @mutex only -when it has been unlocked as many times as it had been locked -before. If @mutex is completely unlocked and another thread is blocked -in a g_static_rec_mutex_lock() call for @mutex, it will be woken and -can lock @mutex itself. - - -@mutex: a #GStaticRecMutex to unlock. - - - - -Works like calling g_static_rec_mutex_lock() for @mutex @depth times. - - -@mutex: a #GStaticRecMutex to lock. -@depth: number of times this mutex has to be unlocked to be completely unlocked. - - - - -Completely unlocks @mutex. If another thread is blocked in a -g_static_rec_mutex_lock() call for @mutex, it will be woken and can -lock @mutex itself. This function returns the number of times that -@mutex has been locked by the current thread. To restore the state -before the call to g_static_rec_mutex_unlock_full() you can call -g_static_rec_mutex_lock_full() with the depth returned by this -function. - - -@mutex: a #GStaticRecMutex to completely unlock. -@Returns: number of times @mutex has been locked by the current thread. - - - - -Releases all resources allocated to a #GStaticRecMutex. - - - -You don't have to call this functions for a #GStaticRecMutex with an -unbounded lifetime, i.e. objects declared 'static', but if you have a -#GStaticRecMutex as a member of a structure and the structure is -freed, you should also free the #GStaticRecMutex. - - -@mutex: a #GStaticRecMutex to be freed. - - - - -The #GStaticRWLock struct represents a read-write lock. A read-write -lock can be used for protecting data that some portions of code only -read from, while others also write. In such situations it is -desirable that several readers can read at once, whereas of course -only one writer may write at a time. Take a look at the following -example: - - -An array with access functions - - GStaticRWLock rwlock = G_STATIC_RW_LOCK_INIT; - - GPtrArray *array; - - gpointer my_array_get (guint index) - { - gpointer retval = NULL; - - if (!array) - return NULL; - - g_static_rw_lock_reader_lock (&rwlock); - - if (index < array->len) - retval = g_ptr_array_index (array, index); - - g_static_rw_lock_reader_unlock (&rwlock); - - return retval; - } - - void my_array_set (guint index, gpointer data) - { - g_static_rw_lock_writer_lock (&rwlock); - - if (!array) - array = g_ptr_array_new (); - - if (index >= array->len) - g_ptr_array_set_size (array, index+1); - - g_ptr_array_index (array, index) = data; - - g_static_rw_lock_writer_unlock (&rwlock); - } - - - - - -This example shows an array which can be accessed by many readers -(the my_array_get() function) simultaneously, -whereas the writers (the my_array_set() function) -will only be allowed once at a time and only if no readers currently access -the array. This is because of the potentially dangerous resizing of the -array. Using these functions is fully multi-thread safe now. - - - -Most of the time, writers should have precedence over readers. That -means, for this implementation, that as soon as a writer wants to lock -the data, no other reader is allowed to lock the data, whereas, of -course, the readers that already have locked the data are allowed to -finish their operation. As soon as the last reader unlocks the data, -the writer will lock it. - - - -Even though #GStaticRWLock is not opaque, it should only be used with -the following functions. - - - -All of the g_static_rw_lock_* functions can be -used even if g_thread_init() has not been called. Then they do -nothing, apart from g_static_rw_lock_*_trylock, -which does nothing but returning %TRUE. - - - - -A read-write lock has a higher overhead than a mutex. For example, both -g_static_rw_lock_reader_lock() and g_static_rw_lock_reader_unlock() -have to lock and unlock a #GStaticMutex, so it takes at least twice the -time to lock and unlock a #GStaticRWLock that it does to lock and unlock a -#GStaticMutex. So only data structures that are accessed by multiple -readers, and which keep the lock for a considerable time justify a -#GStaticRWLock. The above example most probably would fare better with -a #GStaticMutex. - - - - - - -A #GStaticRWLock must be initialized with this macro before it can -be used. This macro can used be to initialize a variable, but it -cannot be assigned to a variable. In that case you have to use -g_static_rw_lock_init(). - - - - - -GStaticRWLock my_lock = G_STATIC_RW_LOCK_INIT; - - - - - - - - -A #GStaticRWLock must be initialized with this function before it can -be used. Alternatively you can initialize it with -#G_STATIC_RW_LOCK_INIT. - - -@lock: a #GStaticRWLock to be initialized. - - - - -Locks @lock for reading. There may be unlimited concurrent locks for -reading of a #GStaticRWLock at the same time. If @lock is already -locked for writing by another thread or if another thread is already -waiting to lock @lock for writing, this function will block until -@lock is unlocked by the other writing thread and no other writing -threads want to lock @lock. This lock has to be unlocked by -g_static_rw_lock_reader_unlock(). - - - -#GStaticRWLock is not recursive. It might seem to be possible to -recursively lock for reading, but that can result in a deadlock, due -to writer preference. - - -@lock: a #GStaticRWLock to lock for reading. - - - - -Tries to lock @lock for reading. If @lock is already locked for -writing by another thread or if another thread is already waiting to -lock @lock for writing, immediately returns %FALSE. Otherwise locks -@lock for reading and returns %TRUE. This lock has to be unlocked by -g_static_rw_lock_reader_unlock(). - - -@lock: a #GStaticRWLock to lock for reading. -@Returns: %TRUE, if @lock could be locked for reading. - - - - -Unlocks @lock. If a thread waits to lock @lock for writing and all -locks for reading have been unlocked, the waiting thread is woken up -and can lock @lock for writing. - - -@lock: a #GStaticRWLock to unlock after reading. - - - - -Locks @lock for writing. If @lock is already locked for writing or -reading by other threads, this function will block until @lock is -completely unlocked and then lock @lock for writing. While this -functions waits to lock @lock, no other thread can lock @lock for -reading. When @lock is locked for writing, no other thread can lock -@lock (neither for reading nor writing). This lock has to be unlocked -by g_static_rw_lock_writer_unlock(). - - -@lock: a #GStaticRWLock to lock for writing. - - - - -Tries to lock @lock for writing. If @lock is already locked (for -either reading or writing) by another thread, it immediately returns -%FALSE. Otherwise it locks @lock for writing and returns %TRUE. This -lock has to be unlocked by g_static_rw_lock_writer_unlock(). - - -@lock: a #GStaticRWLock to lock for writing. -@Returns: %TRUE, if @lock could be locked for writing. - - - - -Unlocks @lock. If a thread is waiting to lock @lock for writing and -all locks for reading have been unlocked, the waiting thread is woken -up and can lock @lock for writing. If no thread is waiting to lock -@lock for writing, and some thread or threads are waiting to lock @lock -for reading, the waiting threads are woken up and can lock @lock for -reading. - - -@lock: a #GStaticRWLock to unlock after writing. - - - - -Releases all resources allocated to @lock. - - - -You don't have to call this functions for a #GStaticRWLock with an -unbounded lifetime, i.e. objects declared 'static', but if you have a -#GStaticRWLock as a member of a structure, and the structure is freed, -you should also free the #GStaticRWLock. - - -@lock: a #GStaticRWLock to be freed. - - - - - -The #GCond struct is an opaque data structure that represents a -condition. Threads can block on a #GCond if they find a certain -condition to be false. If other threads change the state of this -condition they signal the #GCond, and that causes the waiting threads -to be woken up. - - - - -Using GCond to block a thread until a condition is satisfied - -GCond* data_cond = NULL; /* Must be initialized somewhere */ -GMutex* data_mutex = NULL; /* Must be initialized somewhere */ -gpointer current_data = NULL; - -void push_data (gpointer data) -{ - g_mutex_lock (data_mutex); - current_data = data; - g_cond_signal (data_cond); - g_mutex_unlock (data_mutex); -} - -gpointer pop_data () -{ - gpointer data; - - g_mutex_lock (data_mutex); - while (!current_data) - g_cond_wait (data_cond, data_mutex); - data = current_data; - current_data = NULL; - g_mutex_unlock (data_mutex); - return data; -} - - - - - -Whenever a thread calls pop_data() now, it will -wait until current_data is non-%NULL, i.e. until some other thread -has called push_data(). - - - - -It is important to use the g_cond_wait() and g_cond_timed_wait() -functions only inside a loop which checks for the condition to be -true. It is not guaranteed that the waiting thread will find the -condition fulfilled after it wakes up, even if the signaling thread -left the condition in that state: another thread may have altered the -condition before the waiting thread got the chance to be woken up, -even if the condition itself is protected by a #GMutex, like above. - - - - -A #GCond should only be accessed via the following functions. - - - - -All of the g_cond_* functions are actually macros. -Apart from taking their addresses, you can however use them as if they -were functions. - - - - - - - -Creates a new #GCond. This function will abort, if g_thread_init() -has not been called yet. - - -@Returns: a new #GCond. - - - - -If threads are waiting for @cond, exactly one of them is woken up. It -is good practice to hold the same lock as the waiting thread while -calling this function, though not required. - - - -This function can be used even if g_thread_init() has not yet been called, -and, in that case, will do nothing. - - -@cond: a #GCond. - - - - - -If threads are waiting for @cond, all of them are woken up. It is good -practice to lock the same mutex as the waiting threads, while calling -this function, though not required. - - - -This function can be used even if g_thread_init() has not yet been called, -and, in that case, will do nothing. - - -@cond: a #GCond. - - - - - -Waits until this thread is woken up on @cond. The @mutex is unlocked -before falling asleep and locked again before resuming. - - - -This function can be used even if g_thread_init() has not yet been -called, and, in that case, will immediately return. - - -@cond: a #GCond. -@mutex: a #GMutex, that is currently locked. - - - - - -Waits until this thread is woken up on @cond, but not longer than -until the time specified by @abs_time. The @mutex is -unlocked before falling asleep and locked again before resuming. - - - -If @abs_time is %NULL, g_cond_timed_wait() acts like g_cond_wait(). - - - -This function can be used even if g_thread_init() has not yet been -called, and, in that case, will immediately return %TRUE. - - - -To easily calculate @abs_time a combination of g_get_current_time() -and g_time_val_add() can be used. - - -@cond: a #GCond. -@mutex: a #GMutex that is currently locked. -@abs_time: a #GTimeVal, determining the final time. -@Returns: %TRUE if @cond was signalled, or %FALSE on timeout. - - - - - -Destroys the #GCond. - - -@cond: a #GCond. - - - - -The #GPrivate struct is an opaque data structure to represent a thread -private data key. Threads can thereby obtain and set a pointer which -is private to the current thread. -Take our give_me_next_number() example from above. -Suppose we don't want current_number to be shared -between the threads, but instead to be private to each thread. This can be -done as follows: - - -Using GPrivate for per-thread data - - GPrivate* current_number_key = NULL; /* Must be initialized somewhere */ - /* with g_private_new (g_free); */ - - int give_me_next_number () - { - int *current_number = g_private_get (current_number_key); - - if (!current_number) - { - current_number = g_new (int, 1); - *current_number = 0; - g_private_set (current_number_key, current_number); - } - *current_number = calc_next_number (*current_number); - return *current_number; - } - - - - - -Here the pointer belonging to the key current_number_key -is read. If it is %NULL, it has not been set yet. Then get memory for an -integer value, assign this memory to the pointer and write the pointer -back. Now we have an integer value that is private to the current thread. - - - -The #GPrivate struct should only be accessed via the following functions. - - - - -All of the g_private_* functions are actually macros. -Apart from taking their addresses, you can however use them as if they were -functions. - - - - - - - -Creates a new #GPrivate. If @destructor is non-%NULL, it is a pointer -to a destructor function. Whenever a thread ends and the corresponding -pointer keyed to this instance of #GPrivate is non-%NULL, the -destructor is called with this pointer as the argument. - - - - -@destructor is used quite differently from @notify in -g_static_private_set(). - - - - - -A #GPrivate can not be freed. Reuse it instead, if you can, to avoid -shortage, or use #GStaticPrivate. - - - - - -This function will abort if g_thread_init() has not been called yet. - - - -@destructor: a function to destroy the data keyed to #GPrivate when a -thread ends. -@Returns: a new #GPrivate. - - - - - -Returns the pointer keyed to @private_key for the current thread. -If g_private_set() hasn't been called for the -current @private_key and thread yet, this pointer will be %NULL. - - - -This function can be used even if g_thread_init() has not yet been called, and, -in that case, will return the value of @private_key casted to #gpointer. -Note however, that private data set before g_thread_init() will -not be retained after the call. Instead, %NULL -will be returned in all threads directly after g_thread_init(), regardless of -any g_private_set() calls issued before threading system intialization. - - -@private_key: a #GPrivate. -@Returns: the corresponding pointer. - - - - - -Sets the pointer keyed to @private_key for the current thread. - - - -This function can be used even if g_thread_init() has not yet been -called, and, in that case, will set @private_key to @data casted to #GPrivate*. -See g_private_get() for resulting caveats. - - -@private_key: a #GPrivate. -@data: the new pointer. - - - - - -A #GStaticPrivate works almost like a #GPrivate, but it has one -significant advantage. It doesn't need to be created at run-time like -a #GPrivate, but can be defined at compile-time. This is similar to -the difference between #GMutex and #GStaticMutex. Now look at our -give_me_next_number() example with #GStaticPrivate: - - - - -Using GStaticPrivate for per-thread data - - int give_me_next_number () - { - static GStaticPrivate current_number_key = G_STATIC_PRIVATE_INIT; - int *current_number = g_static_private_get (&current_number_key); - - if (!current_number) - { - current_number = g_new (int,1); - *current_number = 0; - g_static_private_set (&current_number_key, current_number, g_free); - } - *current_number = calc_next_number (*current_number); - return *current_number; - } - - - - - - - -Every #GStaticPrivate must be initialized with this macro, before it can -be used. - - - - - -GStaticPrivate my_private = G_STATIC_PRIVATE_INIT; - - - - - - - - -Initializes @private_key. Alternatively you can initialize it with -#G_STATIC_PRIVATE_INIT. - - -@private_key: a #GStaticPrivate to be initialized. - - - - -Works like g_private_get() only for a #GStaticPrivate. - - - -This function works even if g_thread_init() has not yet been called. - - -@private_key: a #GStaticPrivate. -@Returns: the corresponding pointer. - - - - -Sets the pointer keyed to @private_key for the current thread and the -function @notify to be called with that pointer (%NULL or non-%NULL), -whenever the pointer is set again or whenever the current thread ends. - - - -This function works even if g_thread_init() has not yet been -called. If g_thread_init() is called later, the @data keyed to -@private_key will be inherited only by the main thread, i.e. the one that -called g_thread_init(). - - - - -@notify is used quite differently from @destructor in -g_private_new(). - - - -@private_key: a #GStaticPrivate. -@data: the new pointer. -@notify: a function to be called with the pointer whenever the -current thread ends or sets this pointer again. - - - - -Releases all resources allocated to @private_key. - - - -You don't have to call this functions for a #GStaticPrivate with an -unbounded lifetime, i.e. objects declared 'static', but if you have a -#GStaticPrivate as a member of a structure and the structure is freed, -you should also free the #GStaticPrivate. - - -@private_key: a #GStaticPrivate to be freed. - - - - -A GOnce struct controls a one-time initialization -function. Any one-time initialization function must have its own unique -GOnce struct. - - -@status: the status of the #GOnce -@retval: the value returned by the call to the function, if @status - is %G_ONCE_STATUS_READY -@Since: 2.4 - - - -The possible statuses of a one-time initialization function controlled by a #GOnce struct. - - -@G_ONCE_STATUS_NOTCALLED: the function has not been called yet. -@G_ONCE_STATUS_PROGRESS: the function call is currently in progress. -@G_ONCE_STATUS_READY: the function has been called. -@Since: 2.4 - - - -A #GOnce must be initialized with this macro before it can be used. - - - - -GOnce my_once = G_ONCE_INIT; - - - - -@Since: 2.4 - - - - -The first call to this routine by a process with a given #GOnce struct calls -@func with the given argument. Thereafter, subsequent calls to g_once() with -the same #GOnce struct do not call @func again, but return the stored result -of the first call. On return from g_once(), the status of @once will be -%G_ONCE_STATUS_READY. - - -For example, a mutex or a thread-specific data key must be created exactly -once. In a threaded environment, calling g_once() ensures that the -initialization is serialized across multiple threads. - - -Calling g_once() recursively on the same #GOnce struct in @func will lead -to a deadlock. - - - - -gpointer -get_debug_flags () -{ - static GOnce my_once = G_ONCE_INIT; - - g_once (&my_once, parse_debug_flags, NULL); - - return my_once.retval; -} - - - - -@once: a #GOnce structure -@func: the #GThreadFunc function associated to @once. This function is - called only once, regardless of the number of times it and its - associated #GOnce struct are passed to g_once() . -@arg: data to be passed to @func -@Since: 2.4 - - - - -Function to be called when starting a critical initialization section. -The argument @value_location must point to a static 0-initialized variable -that will be set to a value other than 0 at the end of the initialization -section. -In combination with g_once_init_leave() and the unique address @value_location, -it can be ensured that an initialization section will be executed only once -during a program's life time, and that concurrent threads are blocked until -initialization completed. To be used in constructs like this: - - - - -static gsize initialization_value = 0; -if (g_once_init_enter (&initialization_value)) /* section start */ - { - gsize setup_value = 42; /* initialization code here */ - g_once_init_leave (&initialization_value, setup_value); /* section end */ - } -/* use initialization_value here */ - - - -@value_location: location of a static initializable variable containing 0. -@Returns: %TRUE if the initialization section should be entered, %FALSE and blocks otherwise -@Since: 2.14 - - - - -Counterpart to g_once_init_enter(). Expects a location of a static -0-initialized initialization variable, and an initialization value other -than 0. Sets the variable to the initialization value, and releases -concurrent threads blocking in g_once_init_enter() on this initialization -variable. - - -@value_location: location of a static initializable variable containing 0. -@initialization_value: new non-0 value for *@value_location. -@Since: 2.14 - - diff --git a/glib/gthread.c b/glib/gthread.c index 0fe367b95..cb5c547db 100644 --- a/glib/gthread.c +++ b/glib/gthread.c @@ -21,6 +21,8 @@ * Boston, MA 02111-1307, USA. */ +/* Prelude {{{1 ----------------------------------------------------------- */ + /* * Modified by the GLib Team and others 1997-2000. See the AUTHORS * file for a list of people on the GLib Team. See the ChangeLog @@ -56,12 +58,186 @@ #include "galias.h" +/** + * SECTION: threads + * @title: Threads + * @short_description: thread abstraction; including threads, different + * mutexes, conditions and thread private data + * @see_also: #GThreadPool, #GAsyncQueue + * + * Threads act almost like processes, but unlike processes all threads + * of one process share the same memory. This is good, as it provides + * easy communication between the involved threads via this shared + * memory, and it is bad, because strange things (so called + * "Heisenbugs") might happen if the program is not carefully designed. + * In particular, due to the concurrent nature of threads, no + * assumptions on the order of execution of code running in different + * threads can be made, unless order is explicitly forced by the + * programmer through synchronization primitives. + * + * The aim of the thread related functions in GLib is to provide a + * portable means for writing multi-threaded software. There are + * primitives for mutexes to protect the access to portions of memory + * (#GMutex, #GStaticMutex, #G_LOCK_DEFINE, #GStaticRecMutex and + * #GStaticRWLock). There are primitives for condition variables to + * allow synchronization of threads (#GCond). There are primitives for + * thread-private data - data that every thread has a private instance + * of (#GPrivate, #GStaticPrivate). Last but definitely not least there + * are primitives to portably create and manage threads (#GThread). + * + * The threading system is initialized with g_thread_init(), which + * takes an optional custom thread implementation or %NULL for the + * default implementation. If you want to call g_thread_init() with a + * non-%NULL argument this must be done before executing any other GLib + * functions (except g_mem_set_vtable()). This is a requirement even if + * no threads are in fact ever created by the process. + * + * Calling g_thread_init() with a %NULL argument is somewhat more + * relaxed. You may call any other glib functions in the main thread + * before g_thread_init() as long as g_thread_init() is not called from + * a glib callback, or with any locks held. However, many libraries + * above glib does not support late initialization of threads, so doing + * this should be avoided if possible. + * + * Please note that since version 2.24 the GObject initialization + * function g_type_init() initializes threads (with a %NULL argument), + * so most applications, including those using Gtk+ will run with + * threads enabled. If you want a special thread implementation, make + * sure you call g_thread_init() before g_type_init() is called. + * + * After calling g_thread_init(), GLib is completely thread safe (all + * global data is automatically locked), but individual data structure + * instances are not automatically locked for performance reasons. So, + * for example you must coordinate accesses to the same #GHashTable + * from multiple threads. The two notable exceptions from this rule + * are #GMainLoop and #GAsyncQueue, which are + * threadsafe and needs no further application-level locking to be + * accessed from multiple threads. + * + * To help debugging problems in multithreaded applications, GLib + * supports error-checking mutexes that will give you helpful error + * messages on common problems. To use error-checking mutexes, define + * the symbol #G_ERRORCHECK_MUTEXES when compiling the application. + **/ + +/** + * G_THREADS_IMPL_POSIX: + * + * This macro is defined if POSIX style threads are used. + **/ + +/** + * G_THREADS_ENABLED: + * + * This macro is defined if GLib was compiled with thread support. This + * does not necessarily mean that there is a thread implementation + * available, but it does mean that the infrastructure is in place and + * that once you provide a thread implementation to g_thread_init(), + * GLib will be multi-thread safe. If #G_THREADS_ENABLED is not + * defined, then Glib is not, and cannot be, multi-thread safe. + **/ + +/** + * G_THREADS_IMPL_NONE: + * + * This macro is defined if no thread implementation is used. You can, + * however, provide one to g_thread_init() to make GLib multi-thread + * safe. + **/ + +/* G_LOCK Documentation {{{1 ---------------------------------------------- */ + +/* IMPLEMENTATION NOTE: + * + * G_LOCK_DEFINE and friends are convenience macros defined in + * gthread.h. Their documentation lives here. + */ + +/** + * G_LOCK_DEFINE: + * @name: the name of the lock. + * + * The %G_LOCK_* macros provide a convenient interface to #GStaticMutex + * with the advantage that they will expand to nothing in programs + * compiled against a thread-disabled GLib, saving code and memory + * there. #G_LOCK_DEFINE defines a lock. It can appear anywhere + * variable definitions may appear in programs, i.e. in the first block + * of a function or outside of functions. The @name parameter will be + * mangled to get the name of the #GStaticMutex. This means that you + * can use names of existing variables as the parameter - e.g. the name + * of the variable you intent to protect with the lock. Look at our + * give_me_next_number() example using the + * %G_LOCK_* macros: + * + * Using the %G_LOCK_* convenience macros + * G_LOCK_DEFINE (current_number); int + * give_me_next_number () { static int current_number = 0; int + * ret_val; G_LOCK (current_number); ret_val = current_number = + * calc_next_number (current_number); G_UNLOCK (current_number); return + * ret_val; } + **/ + +/** + * G_LOCK_DEFINE_STATIC: + * @name: the name of the lock. + * + * This works like #G_LOCK_DEFINE, but it creates a static object. + **/ + +/** + * G_LOCK_EXTERN: + * @name: the name of the lock. + * + * This declares a lock, that is defined with #G_LOCK_DEFINE in another + * module. + **/ + +/** + * G_LOCK: + * @name: the name of the lock. + * + * Works like g_mutex_lock(), but for a lock defined with + * #G_LOCK_DEFINE. + **/ + +/** + * G_TRYLOCK: + * @name: the name of the lock. + * @Returns: %TRUE, if the lock could be locked. + * + * Works like g_mutex_trylock(), but for a lock defined with + * #G_LOCK_DEFINE. + **/ + +/** + * G_UNLOCK: + * @name: the name of the lock. + * + * Works like g_mutex_unlock(), but for a lock defined with + * #G_LOCK_DEFINE. + **/ + +/* GThreadError {{{1 ------------------------------------------------------- */ +/** + * GThreadError: + * @G_THREAD_ERROR_AGAIN: a thread couldn't be created due to resource + * shortage. Try again later. + * + * Possible errors of thread related functions. + **/ + +/** + * G_THREAD_ERROR: + * + * The error domain of the GLib thread subsystem. + **/ GQuark g_thread_error_quark (void) { return g_quark_from_static_string ("g_thread_error"); } +/* Miscellaneous Structures {{{1 ------------------------------------------ */ /* Keep this in sync with GRealThread in gmain.c! */ typedef struct _GRealThread GRealThread; struct _GRealThread @@ -86,31 +262,577 @@ static guint64 gettime (void); guint64 (*g_thread_gettime) (void) = gettime; -/* Global variables */ +/* Global Variables {{{1 -------------------------------------------------- */ static GSystemThread zero_thread; /* This is initialized to all zero */ gboolean g_thread_use_default_impl = TRUE; + +/** + * g_thread_supported: + * @Returns: %TRUE, if the thread system is initialized. + * + * This function returns %TRUE if the thread system is initialized, and + * %FALSE if it is not. + * + * This function is actually a macro. Apart from taking the + * address of it you can however use it as if it was a + * function. + **/ + +/* IMPLEMENTATION NOTE: + * + * g_thread_supported() is just returns g_threads_got_initialized + */ gboolean g_threads_got_initialized = FALSE; + +/* Thread Implementation Virtual Function Table {{{1 ---------------------- */ +/* Virtual Function Table Documentation {{{2 ------------------------------ */ +/** + * GThreadFunctions: + * @mutex_new: virtual function pointer for g_mutex_new() + * @mutex_lock: virtual function pointer for g_mutex_lock() + * @mutex_trylock: virtual function pointer for g_mutex_trylock() + * @mutex_unlock: virtual function pointer for g_mutex_unlock() + * @mutex_free: virtual function pointer for g_mutex_free() + * @cond_new: virtual function pointer for g_cond_new() + * @cond_signal: virtual function pointer for g_cond_signal() + * @cond_broadcast: virtual function pointer for g_cond_broadcast() + * @cond_wait: virtual function pointer for g_cond_wait() + * @cond_timed_wait: virtual function pointer for g_cond_timed_wait() + * @cond_free: virtual function pointer for g_cond_free() + * @private_new: virtual function pointer for g_private_new() + * @private_get: virtual function pointer for g_private_get() + * @private_set: virtual function pointer for g_private_set() + * @thread_create: virtual function pointer for g_thread_create() + * @thread_yield: virtual function pointer for g_thread_yield() + * @thread_join: virtual function pointer for g_thread_join() + * @thread_exit: virtual function pointer for g_thread_exit() + * @thread_set_priority: virtual function pointer for + * g_thread_set_priority() + * @thread_self: virtual function pointer for g_thread_self() + * @thread_equal: used internally by recursive mutex locks and by some + * assertion checks + * + * This function table is used by g_thread_init() to initialize the + * thread system. The functions in the table are directly used by their + * g_* prepended counterparts (described in this document). For + * example, if you call g_mutex_new() then mutex_new() from the table + * provided to g_thread_init() will be called. + * + * Do not use this struct unless you know what you are + * doing. + **/ + +/* IMPLEMENTATION NOTE: + * + * g_thread_functions_for_glib_use is a global symbol that gets used by + * most of the "primative" threading calls. g_mutex_lock(), for + * example, is just a macro that calls the appropriate virtual function + * out of this table. + * + * For that reason, all of those macros are documented here. + */ GThreadFunctions g_thread_functions_for_glib_use = { - (GMutex*(*)())g_thread_fail, /* mutex_new */ - NULL, /* mutex_lock */ - NULL, /* mutex_trylock */ - NULL, /* mutex_unlock */ - NULL, /* mutex_free */ - (GCond*(*)())g_thread_fail, /* cond_new */ - NULL, /* cond_signal */ - NULL, /* cond_broadcast */ - NULL, /* cond_wait */ - NULL, /* cond_timed_wait */ - NULL, /* cond_free */ - (GPrivate*(*)(GDestroyNotify))g_thread_fail, /* private_new */ - NULL, /* private_get */ - NULL, /* private_set */ +/* GMutex Virtual Functions {{{2 ------------------------------------------ */ + +/** + * GMutex: + * + * The #GMutex struct is an opaque data structure to represent a mutex + * (mutual exclusion). It can be used to protect data against shared + * access. Take for example the following function: + * + * + * A function which will not work in a threaded environment + * + * int + * give_me_next_number (void) + * { + * static int current_number = 0; + * + * /* now do a very complicated calculation to calculate the new + * * number, this might for example be a random number generator + * */ + * current_number = calc_next_number (current_number); + * + * return current_number; + * } + * + * + * + * It is easy to see that this won't work in a multi-threaded + * application. There current_number must be protected against shared + * access. A first naive implementation would be: + * + * + * The wrong way to write a thread-safe function + * + * int + * give_me_next_number (void) + * { + * static int current_number = 0; + * int ret_val; + * static GMutex * mutex = NULL; + * + * if (!mutex) mutex = g_mutex_new (); + * + * g_mutex_lock (mutex); + * ret_val = current_number = calc_next_number (current_number); + * g_mutex_unlock (mutex); + * + * return ret_val; + * } + * + * + * + * This looks like it would work, but there is a race condition while + * constructing the mutex and this code cannot work reliable. Please do + * not use such constructs in your own programs! One working solution + * is: + * + * + * A correct thread-safe function + * + * static GMutex *give_me_next_number_mutex = NULL; + * + * /* this function must be called before any call to + * * give_me_next_number() + * * + * * it must be called exactly once. + * */ + * void + * init_give_me_next_number (void) + * { + * g_assert (give_me_next_number_mutex == NULL); + * give_me_next_number_mutex = g_mutex_new (); + * } + * + * int + * give_me_next_number (void) + * { + * static int current_number = 0; + * int ret_val; + * + * g_mutex_lock (give_me_next_number_mutex); + * ret_val = current_number = calc_next_number (current_number); + * g_mutex_unlock (give_me_next_number_mutex); + * + * return ret_val; + * } + * + * + * + * #GStaticMutex provides a simpler and safer way of doing this. + * + * If you want to use a mutex, and your code should also work without + * calling g_thread_init() first, then you can not use a #GMutex, as + * g_mutex_new() requires that the thread system be initialized. Use a + * #GStaticMutex instead. + * + * A #GMutex should only be accessed via the following functions. + * + * All of the g_mutex_* functions are + * actually macros. Apart from taking their addresses, you can however + * use them as if they were functions. + **/ + +/** + * g_mutex_new: + * @Returns: a new #GMutex. + * + * Creates a new #GMutex. + * + * This function will abort if g_thread_init() has not been + * called yet. + **/ + (GMutex*(*)())g_thread_fail, + +/** + * g_mutex_lock: + * @mutex: a #GMutex. + * + * Locks @mutex. If @mutex is already locked by another thread, the + * current thread will block until @mutex is unlocked by the other + * thread. + * + * This function can be used even if g_thread_init() has not yet been + * called, and, in that case, will do nothing. + * + * #GMutex is neither guaranteed to be recursive nor to be + * non-recursive, i.e. a thread could deadlock while calling + * g_mutex_lock(), if it already has locked @mutex. Use + * #GStaticRecMutex, if you need recursive mutexes. + **/ + NULL, + +/** + * g_mutex_trylock: + * @mutex: a #GMutex. + * @Returns: %TRUE, if @mutex could be locked. + * + * Tries to lock @mutex. If @mutex is already locked by another thread, + * it immediately returns %FALSE. Otherwise it locks @mutex and returns + * %TRUE. + * + * This function can be used even if g_thread_init() has not yet been + * called, and, in that case, will immediately return %TRUE. + * + * #GMutex is neither guaranteed to be recursive nor to be + * non-recursive, i.e. the return value of g_mutex_trylock() could be + * both %FALSE or %TRUE, if the current thread already has locked + * @mutex. Use #GStaticRecMutex, if you need recursive + * mutexes. + **/ + NULL, + +/** + * g_mutex_unlock: + * @mutex: a #GMutex. + * + * Unlocks @mutex. If another thread is blocked in a g_mutex_lock() + * call for @mutex, it will be woken and can lock @mutex itself. + * + * This function can be used even if g_thread_init() has not yet been + * called, and, in that case, will do nothing. + **/ + NULL, + +/** + * g_mutex_free: + * @mutex: a #GMutex. + * + * Destroys @mutex. + * + * Calling g_mutex_free() on a locked mutex may result in + * undefined behaviour. + **/ + NULL, + +/* GCond Virtual Functions {{{2 ------------------------------------------ */ + +/** + * GCond: + * + * The #GCond struct is an opaque data structure that represents a + * condition. Threads can block on a #GCond if they find a certain + * condition to be false. If other threads change the state of this + * condition they signal the #GCond, and that causes the waiting + * threads to be woken up. + * + * + * + * Using GCond to block a thread until a condition is satisfied + * + * + * GCond* data_cond = NULL; /* Must be initialized somewhere */ + * GMutex* data_mutex = NULL; /* Must be initialized somewhere */ + * gpointer current_data = NULL; + * + * void + * push_data (gpointer data) + * { + * g_mutex_lock (data_mutex); + * current_data = data; + * g_cond_signal (data_cond); + * g_mutex_unlock (data_mutex); + * } + * + * gpointer + * pop_data (void) + * { + * gpointer data; + * + * g_mutex_lock (data_mutex); + * while (!current_data) + * g_cond_wait (data_cond, data_mutex); + * data = current_data; + * current_data = NULL; + * g_mutex_unlock (data_mutex); + * + * return data; + * } + * + * + * + * Whenever a thread calls pop_data() now, it will + * wait until current_data is non-%NULL, i.e. until some other thread + * has called push_data(). + * + * It is important to use the g_cond_wait() and + * g_cond_timed_wait() functions only inside a loop which checks for the + * condition to be true. It is not guaranteed that the waiting thread + * will find the condition fulfilled after it wakes up, even if the + * signaling thread left the condition in that state: another thread may + * have altered the condition before the waiting thread got the chance + * to be woken up, even if the condition itself is protected by a + * #GMutex, like above. + * + * A #GCond should only be accessed via the following functions. + * + * All of the g_cond_* functions are + * actually macros. Apart from taking their addresses, you can however + * use them as if they were functions. + **/ + +/** + * g_cond_new: + * @Returns: a new #GCond. + * + * Creates a new #GCond. This function will abort, if g_thread_init() + * has not been called yet. + **/ + (GCond*(*)())g_thread_fail, + +/** + * g_cond_signal: + * @cond: a #GCond. + * + * If threads are waiting for @cond, exactly one of them is woken up. + * It is good practice to hold the same lock as the waiting thread + * while calling this function, though not required. + * + * This function can be used even if g_thread_init() has not yet been + * called, and, in that case, will do nothing. + **/ + NULL, + +/** + * g_cond_broadcast: + * @cond: a #GCond. + * + * If threads are waiting for @cond, all of them are woken up. It is + * good practice to lock the same mutex as the waiting threads, while + * calling this function, though not required. + * + * This function can be used even if g_thread_init() has not yet been + * called, and, in that case, will do nothing. + **/ + NULL, + +/** + * g_cond_wait: + * @cond: a #GCond. + * @mutex: a #GMutex, that is currently locked. + * + * Waits until this thread is woken up on @cond. The @mutex is unlocked + * before falling asleep and locked again before resuming. + * + * This function can be used even if g_thread_init() has not yet been + * called, and, in that case, will immediately return. + **/ + NULL, + +/** + * g_cond_timed_wait: + * @cond: a #GCond. + * @mutex: a #GMutex that is currently locked. + * @abs_time: a #GTimeVal, determining the final time. + * @Returns: %TRUE if @cond was signalled, or %FALSE on timeout. + * + * Waits until this thread is woken up on @cond, but not longer than + * until the time specified by @abs_time. The @mutex is unlocked before + * falling asleep and locked again before resuming. + * + * If @abs_time is %NULL, g_cond_timed_wait() acts like g_cond_wait(). + * + * This function can be used even if g_thread_init() has not yet been + * called, and, in that case, will immediately return %TRUE. + * + * To easily calculate @abs_time a combination of g_get_current_time() + * and g_time_val_add() can be used. + **/ + NULL, + +/** + * g_cond_free: + * @cond: a #GCond. + * + * Destroys the #GCond. + **/ + NULL, + +/* GPrivate Virtual Functions {{{2 --------------------------------------- */ + +/** + * GPrivate: + * + * The #GPrivate struct is an opaque data structure to represent a + * thread private data key. Threads can thereby obtain and set a + * pointer which is private to the current thread. Take our + * give_me_next_number() example from + * above. Suppose we don't want current_number to be + * shared between the threads, but instead to be private to each thread. + * This can be done as follows: + * + * + * Using GPrivate for per-thread data + * + * GPrivate* current_number_key = NULL; /* Must be initialized somewhere + * with g_private_new (g_free); a;/ + * + * int + * give_me_next_number (void) + * { + * int *current_number = g_private_get (current_number_key); + * + * if (!current_number) + * { + * current_number = g_new (int, 1); + * *current_number = 0; + * g_private_set (current_number_key, current_number); + * } + * + * *current_number = calc_next_number (*current_number); + * + * return *current_number; + * } + * + * + * + * Here the pointer belonging to the key + * current_number_key is read. If it is %NULL, it has + * not been set yet. Then get memory for an integer value, assign this + * memory to the pointer and write the pointer back. Now we have an + * integer value that is private to the current thread. + * + * The #GPrivate struct should only be accessed via the following + * functions. + * + * All of the g_private_* functions are + * actually macros. Apart from taking their addresses, you can however + * use them as if they were functions. + **/ + +/** + * g_private_new: + * @destructor: a function to destroy the data keyed to #GPrivate when + * a thread ends. + * @Returns: a new #GPrivate. + * + * Creates a new #GPrivate. If @destructor is non-%NULL, it is a + * pointer to a destructor function. Whenever a thread ends and the + * corresponding pointer keyed to this instance of #GPrivate is + * non-%NULL, the destructor is called with this pointer as the + * argument. + * + * @destructor is used quite differently from @notify in + * g_static_private_set(). + * + * A #GPrivate can not be freed. Reuse it instead, if you + * can, to avoid shortage, or use #GStaticPrivate. + * + * This function will abort if g_thread_init() has not been + * called yet. + **/ + (GPrivate*(*)(GDestroyNotify))g_thread_fail, + +/** + * g_private_get: + * @private_key: a #GPrivate. + * @Returns: the corresponding pointer. + * + * Returns the pointer keyed to @private_key for the current thread. If + * g_private_set() hasn't been called for the current @private_key and + * thread yet, this pointer will be %NULL. + * + * This function can be used even if g_thread_init() has not yet been + * called, and, in that case, will return the value of @private_key + * casted to #gpointer. Note however, that private data set + * before g_thread_init() will + * not be retained after the + * call. Instead, %NULL will be returned in all threads directly after + * g_thread_init(), regardless of any g_private_set() calls issued + * before threading system intialization. + **/ + NULL, + +/** + * g_private_set: + * @private_key: a #GPrivate. + * @data: the new pointer. + * + * Sets the pointer keyed to @private_key for the current thread. + * + * This function can be used even if g_thread_init() has not yet been + * called, and, in that case, will set @private_key to @data casted to + * #GPrivate*. See g_private_get() for resulting caveats. + **/ + NULL, + +/* GThread Virtual Functions {{{2 ---------------------------------------- */ +/** + * GThread: + * + * The #GThread struct represents a running thread. It has three public + * read-only members, but the underlying struct is bigger, so you must + * not copy this struct. + * + * Resources for a joinable thread are not fully released + * until g_thread_join() is called for that thread. + **/ + +/** + * GThreadFunc: + * @data: data passed to the thread. + * @Returns: the return value of the thread, which will be returned by + * g_thread_join(). + * + * Specifies the type of the @func functions passed to + * g_thread_create() or g_thread_create_full(). + **/ + +/** + * GThreadPriority: + * @G_THREAD_PRIORITY_LOW: a priority lower than normal + * @G_THREAD_PRIORITY_NORMAL: the default priority + * @G_THREAD_PRIORITY_HIGH: a priority higher than normal + * @G_THREAD_PRIORITY_URGENT: the highest priority + * + * Specifies the priority of a thread. + * + * It is not guaranteed that threads with different priorities + * really behave accordingly. On some systems (e.g. Linux) there are no + * thread priorities. On other systems (e.g. Solaris) there doesn't + * seem to be different scheduling for different priorities. All in all + * try to avoid being dependent on priorities. + **/ + +/** + * g_thread_create: + * @func: a function to execute in the new thread. + * @data: an argument to supply to the new thread. + * @joinable: should this thread be joinable? + * @error: return location for error. + * @Returns: the new #GThread on success. + * + * This function creates a new thread with the default priority. + * + * If @joinable is %TRUE, you can wait for this threads termination + * calling g_thread_join(). Otherwise the thread will just disappear + * when it terminates. + * + * The new thread executes the function @func with the argument @data. + * If the thread was created successfully, it is returned. + * + * @error can be %NULL to ignore errors, or non-%NULL to report errors. + * The error is set, if and only if the function returns %NULL. + **/ (void(*)(GThreadFunc, gpointer, gulong, gboolean, gboolean, GThreadPriority, - gpointer, GError**))g_thread_fail, /* thread_create */ - NULL, /* thread_yield */ + gpointer, GError**))g_thread_fail, + +/** + * g_thread_yield: + * + * Gives way to other threads waiting to be scheduled. + * + * This function is often used as a method to make busy wait less evil. + * But in most cases you will encounter, there are better methods to do + * that. So in general you shouldn't use this function. + **/ + NULL, + NULL, /* thread_join */ NULL, /* thread_exit */ NULL, /* thread_set_priority */ @@ -118,7 +840,7 @@ GThreadFunctions g_thread_functions_for_glib_use = { NULL /* thread_equal */ }; -/* Local data */ +/* Local Data {{{1 -------------------------------------------------------- */ static GMutex *g_once_mutex = NULL; static GCond *g_once_cond = NULL; @@ -129,7 +851,44 @@ static GSList* g_once_init_list = NULL; G_LOCK_DEFINE_STATIC (g_thread); +/* Initialisation {{{1 ---------------------------------------------------- */ + #ifdef G_THREADS_ENABLED +/** + * g_thread_init: + * @vtable: a function table of type #GThreadFunctions, that provides + * the entry points to the thread system to be used. + * + * If you use GLib from more than one thread, you must initialize the + * thread system by calling g_thread_init(). Most of the time you will + * only have to call g_thread_init (NULL). + * + * Do not call g_thread_init() with a non-%NULL parameter unless + * you really know what you are doing. + * + * g_thread_init() must not be called directly or indirectly as a + * callback from GLib. Also no mutexes may be currently locked while + * calling g_thread_init(). + * + * g_thread_init() changes the way in which #GTimer measures + * elapsed time. As a consequence, timers that are running while + * g_thread_init() is called may report unreliable times. + * + * Calling g_thread_init() multiple times is allowed (since version + * 2.24), but nothing happens except for the first call. If the + * argument is non-%NULL on such a call a warning will be printed, but + * otherwise the argument is ignored. + * + * If no thread system is available and @vtable is %NULL or if not all + * elements of @vtable are non-%NULL, then g_thread_init() will abort. + * + * To use g_thread_init() in your program, you have to link with + * the libraries that the command pkg-config --libs + * gthread-2.0 outputs. This is not the case for all the + * other thread related functions of GLib. Those can be used without + * having to link with the thread libraries. + **/ + /* This must be called only once, before any threads are created. * It will only be called from g_thread_init() in -lgthread. */ @@ -173,6 +932,80 @@ g_thread_init_glib (void) } #endif /* G_THREADS_ENABLED */ +/* The following sections implement: GOnce, GStaticMutex, GStaticRecMutex, + * GStaticPrivate, + **/ + +/* GOnce {{{1 ------------------------------------------------------------- */ + +/** + * GOnce: + * @status: the status of the #GOnce + * @retval: the value returned by the call to the function, if @status + * is %G_ONCE_STATUS_READY + * + * A #GOnce struct controls a one-time initialization function. Any + * one-time initialization function must have its own unique #GOnce + * struct. + * + * Since: 2.4 + **/ + +/** + * G_ONCE_INIT: + * + * A #GOnce must be initialized with this macro before it can be used. + * + * + * GOnce my_once = G_ONCE_INIT; + * + * + * Since: 2.4 + **/ + +/** + * GOnceStatus: + * @G_ONCE_STATUS_NOTCALLED: the function has not been called yet. + * @G_ONCE_STATUS_PROGRESS: the function call is currently in progress. + * @G_ONCE_STATUS_READY: the function has been called. + * + * The possible statuses of a one-time initialization function + * controlled by a #GOnce struct. + * + * Since: 2.4 + **/ + +/** + * g_once: + * @once: a #GOnce structure + * @func: the #GThreadFunc function associated to @once. This function + * is called only once, regardless of the number of times it and + * its associated #GOnce struct are passed to g_once(). + * @arg: data to be passed to @func + * + * The first call to this routine by a process with a given #GOnce + * struct calls @func with the given argument. Thereafter, subsequent + * calls to g_once() with the same #GOnce struct do not call @func + * again, but return the stored result of the first call. On return + * from g_once(), the status of @once will be %G_ONCE_STATUS_READY. + * + * For example, a mutex or a thread-specific data key must be created + * exactly once. In a threaded environment, calling g_once() ensures + * that the initialization is serialized across multiple threads. + * + * Calling g_once() recursively on the same #GOnce struct in + * @func will lead to a deadlock. + * + * + * gpointer get_debug_flags () { + * static GOnce my_once = G_ONCE_INIT; + * g_once (&my_once, parse_debug_flags, NULL); + * return my_once.retval; + * } + * + * + * Since: 2.4 + **/ gpointer g_once_impl (GOnce *once, GThreadFunc func, @@ -200,6 +1033,40 @@ g_once_impl (GOnce *once, return once->retval; } +/** + * g_once_init_enter: + * @value_location: location of a static initializable variable + * containing 0. + * @Returns: %TRUE if the initialization section should be entered, + * %FALSE and blocks otherwise + * + * Function to be called when starting a critical initialization + * section. The argument @value_location must point to a static + * 0-initialized variable that will be set to a value other than 0 at + * the end of the initialization section. In combination with + * g_once_init_leave() and the unique address @value_location, it can + * be ensured that an initialization section will be executed only once + * during a program's life time, and that concurrent threads are + * blocked until initialization completed. To be used in constructs + * like this: + * + * + * + * static gsize initialization_value = 0; + * + * if (g_once_init_enter (&initialization_value)) + * { + * gsize setup_value = 42; /* initialization code here */ + * + * g_once_init_leave (&initialization_value, setup_value); + * } + * + * /* use initialization_value here */ + * + * + * + * Since: 2.14 + **/ gboolean g_once_init_enter_impl (volatile gsize *value_location) { @@ -221,6 +1088,20 @@ g_once_init_enter_impl (volatile gsize *value_location) return need_init; } +/** + * g_once_init_leave: + * @value_location: location of a static initializable variable + * containing 0. + * @initialization_value: new non-0 value for *@value_location. + * + * Counterpart to g_once_init_enter(). Expects a location of a static + * 0-initialized initialization variable, and an initialization value + * other than 0. Sets the variable to the initialization value, and + * releases concurrent threads blocking in g_once_init_enter() on this + * initialization variable. + * + * Since: 2.14 + **/ void g_once_init_leave (volatile gsize *value_location, gsize initialization_value) @@ -236,6 +1117,68 @@ g_once_init_leave (volatile gsize *value_location, g_mutex_unlock (g_once_mutex); } +/* GStaticMutex {{{1 ------------------------------------------------------ */ + +/** + * GStaticMutex: + * + * A #GStaticMutex works like a #GMutex, but it has one significant + * advantage. It doesn't need to be created at run-time like a #GMutex, + * but can be defined at compile-time. Here is a shorter, easier and + * safer version of our give_me_next_number() + * example: + * + * Using <structname>GStaticMutex</structname> to + * simplify thread-safe programming int + * give_me_next_number () { static int current_number = 0; int + * ret_val; static GStaticMutex mutex = G_STATIC_MUTEX_INIT; + * g_static_mutex_lock (&mutex); ret_val = current_number = + * calc_next_number (current_number); g_static_mutex_unlock + * (&mutex); return ret_val; } + * + * Sometimes you would like to dynamically create a mutex. If you don't + * want to require prior calling to g_thread_init(), because your code + * should also be usable in non-threaded programs, you are not able to + * use g_mutex_new() and thus #GMutex, as that requires a prior call to + * g_thread_init(). In theses cases you can also use a #GStaticMutex. + * It must be initialized with g_static_mutex_init() before using it + * and freed with with g_static_mutex_free() when not needed anymore to + * free up any allocated resources. + * + * Even though #GStaticMutex is not opaque, it should only be used with + * the following functions, as it is defined differently on different + * platforms. + * + * All of the g_static_mutex_* functions apart + * from g_static_mutex_get_mutex can also be used + * even if g_thread_init() has not yet been called. Then they do + * nothing, apart from g_static_mutex_trylock, + * which does nothing but returning %TRUE. + * + * All of the g_static_mutex_* + * functions are actually macros. Apart from taking their addresses, you + * can however use them as if they were functions. + **/ + +/** + * G_STATIC_MUTEX_INIT: + * + * A #GStaticMutex must be initialized with this macro, before it can + * be used. This macro can used be to initialize a variable, but it + * cannot be assigned to a variable. In that case you have to use + * g_static_mutex_init(). + * + * GStaticMutex my_mutex = + * G_STATIC_MUTEX_INIT; + **/ + +/** + * g_static_mutex_init: + * @mutex: a #GStaticMutex to be initialized. + * + * Initializes @mutex. Alternatively you can initialize it with + * #G_STATIC_MUTEX_INIT. + **/ void g_static_mutex_init (GStaticMutex *mutex) { @@ -246,6 +1189,32 @@ g_static_mutex_init (GStaticMutex *mutex) *mutex = init_mutex; } +/* IMPLEMENTATION NOTE: + * + * On some platforms a GStaticMutex is actually a normal GMutex stored + * inside of a structure instead of being allocated dynamically. We can + * only do this for platforms on which we know, in advance, how to + * allocate (size) and initialise (value) that memory. + * + * On other platforms, a GStaticMutex is nothing more than a pointer to + * a GMutex. In that case, the first access we make to the static mutex + * must first allocate the normal GMutex and store it into the pointer. + * + * configure.in writes macros into glibconfig.h to determine if + * g_static_mutex_get_mutex() accesses the sturcture in memory directly + * (on platforms where we are able to do that) or if it ends up here, + * where we may have to allocate the GMutex before returning it. + */ + +/** + * g_static_mutex_get_mutex: + * @mutex: a #GStaticMutex. + * @Returns: the #GMutex corresponding to @mutex. + * + * For some operations (like g_cond_wait()) you must have a #GMutex + * instead of a #GStaticMutex. This function will return the + * corresponding #GMutex for @mutex. + **/ GMutex * g_static_mutex_get_mutex_impl (GMutex** mutex) { @@ -264,6 +1233,50 @@ g_static_mutex_get_mutex_impl (GMutex** mutex) return *mutex; } +/* IMPLEMENTATION NOTE: + * + * g_static_mutex_lock(), g_static_mutex_trylock() and + * g_static_mutex_unlock() are all preprocessor macros that wrap the + * corresponding g_mutex_*() function around a call to + * g_static_mutex_get_mutex(). + */ + +/** + * g_static_mutex_lock: + * @mutex: a #GStaticMutex. + * + * Works like g_mutex_lock(), but for a #GStaticMutex. + **/ + +/** + * g_static_mutex_trylock: + * @mutex: a #GStaticMutex. + * @Returns: %TRUE, if the #GStaticMutex could be locked. + * + * Works like g_mutex_trylock(), but for a #GStaticMutex. + **/ + +/** + * g_static_mutex_unlock: + * @mutex: a #GStaticMutex. + * + * Works like g_mutex_unlock(), but for a #GStaticMutex. + **/ + +/** + * g_static_mutex_free: + * @mutex: a #GStaticMutex to be freed. + * + * Releases all resources allocated to @mutex. + * + * You don't have to call this functions for a #GStaticMutex with an + * unbounded lifetime, i.e. objects declared 'static', but if you have + * a #GStaticMutex as a member of a structure and the structure is + * freed, you should also free the #GStaticMutex. + * + * Calling g_static_mutex_free() on a locked mutex may + * result in undefined behaviour. + **/ void g_static_mutex_free (GStaticMutex* mutex) { @@ -284,6 +1297,49 @@ g_static_mutex_free (GStaticMutex* mutex) *runtime_mutex = NULL; } +/* ------------------------------------------------------------------------ */ + +/** + * GStaticRecMutex: + * + * A #GStaticRecMutex works like a #GStaticMutex, but it can be locked + * multiple times by one thread. If you enter it n times, you have to + * unlock it n times again to let other threads lock it. An exception + * is the function g_static_rec_mutex_unlock_full(): that allows you to + * unlock a #GStaticRecMutex completely returning the depth, (i.e. the + * number of times this mutex was locked). The depth can later be used + * to restore the state of the #GStaticRecMutex by calling + * g_static_rec_mutex_lock_full(). + * + * Even though #GStaticRecMutex is not opaque, it should only be used + * with the following functions. + * + * All of the g_static_rec_mutex_* functions can + * be used even if g_thread_init() has not been called. Then they do + * nothing, apart from g_static_rec_mutex_trylock, + * which does nothing but returning %TRUE. + **/ + +/** + * G_STATIC_REC_MUTEX_INIT: + * + * A #GStaticRecMutex must be initialized with this macro before it can + * be used. This macro can used be to initialize a variable, but it + * cannot be assigned to a variable. In that case you have to use + * g_static_rec_mutex_init(). + * + * GStaticRecMutex my_mutex = + * G_STATIC_REC_MUTEX_INIT; + **/ + +/** + * g_static_rec_mutex_init: + * @mutex: a #GStaticRecMutex to be initialized. + * + * A #GStaticRecMutex must be initialized with this function before it + * can be used. Alternatively you can initialize it with + * #G_STATIC_REC_MUTEX_INIT. + **/ void g_static_rec_mutex_init (GStaticRecMutex *mutex) { @@ -294,6 +1350,15 @@ g_static_rec_mutex_init (GStaticRecMutex *mutex) *mutex = init_mutex; } +/** + * g_static_rec_mutex_lock: + * @mutex: a #GStaticRecMutex to lock. + * + * Locks @mutex. If @mutex is already locked by another thread, the + * current thread will block until @mutex is unlocked by the other + * thread. If @mutex is already locked by the calling thread, this + * functions increases the depth of @mutex and returns immediately. + **/ void g_static_rec_mutex_lock (GStaticRecMutex* mutex) { @@ -316,6 +1381,17 @@ g_static_rec_mutex_lock (GStaticRecMutex* mutex) mutex->depth = 1; } +/** + * g_static_rec_mutex_trylock: + * @mutex: a #GStaticRecMutex to lock. + * @Returns: %TRUE, if @mutex could be locked. + * + * Tries to lock @mutex. If @mutex is already locked by another thread, + * it immediately returns %FALSE. Otherwise it locks @mutex and returns + * %TRUE. If @mutex is already locked by the calling thread, this + * functions increases the depth of @mutex and immediately returns + * %TRUE. + **/ gboolean g_static_rec_mutex_trylock (GStaticRecMutex* mutex) { @@ -342,6 +1418,16 @@ g_static_rec_mutex_trylock (GStaticRecMutex* mutex) return TRUE; } +/** + * g_static_rec_mutex_unlock: + * @mutex: a #GStaticRecMutex to unlock. + * + * Unlocks @mutex. Another thread will be allowed to lock @mutex only + * when it has been unlocked as many times as it had been locked + * before. If @mutex is completely unlocked and another thread is + * blocked in a g_static_rec_mutex_lock() call for @mutex, it will be + * woken and can lock @mutex itself. + **/ void g_static_rec_mutex_unlock (GStaticRecMutex* mutex) { @@ -359,6 +1445,14 @@ g_static_rec_mutex_unlock (GStaticRecMutex* mutex) g_static_mutex_unlock (&mutex->mutex); } +/** + * g_static_rec_mutex_lock_full: + * @mutex: a #GStaticRecMutex to lock. + * @depth: number of times this mutex has to be unlocked to be + * completely unlocked. + * + * Works like calling g_static_rec_mutex_lock() for @mutex @depth times. + **/ void g_static_rec_mutex_lock_full (GStaticRecMutex *mutex, guint depth) @@ -384,6 +1478,20 @@ g_static_rec_mutex_lock_full (GStaticRecMutex *mutex, mutex->depth = depth; } +/** + * g_static_rec_mutex_unlock_full: + * @mutex: a #GStaticRecMutex to completely unlock. + * @Returns: number of times @mutex has been locked by the current + * thread. + * + * Completely unlocks @mutex. If another thread is blocked in a + * g_static_rec_mutex_lock() call for @mutex, it will be woken and can + * lock @mutex itself. This function returns the number of times that + * @mutex has been locked by the current thread. To restore the state + * before the call to g_static_rec_mutex_unlock_full() you can call + * g_static_rec_mutex_lock_full() with the depth returned by this + * function. + **/ guint g_static_rec_mutex_unlock_full (GStaticRecMutex *mutex) { @@ -403,6 +1511,17 @@ g_static_rec_mutex_unlock_full (GStaticRecMutex *mutex) return depth; } +/** + * g_static_rec_mutex_free: + * @mutex: a #GStaticRecMutex to be freed. + * + * Releases all resources allocated to a #GStaticRecMutex. + * + * You don't have to call this functions for a #GStaticRecMutex with an + * unbounded lifetime, i.e. objects declared 'static', but if you have + * a #GStaticRecMutex as a member of a structure and the structure is + * freed, you should also free the #GStaticRecMutex. + **/ void g_static_rec_mutex_free (GStaticRecMutex *mutex) { @@ -411,12 +1530,60 @@ g_static_rec_mutex_free (GStaticRecMutex *mutex) g_static_mutex_free (&mutex->mutex); } +/* GStaticPrivate {{{1 ---------------------------------------------------- */ + +/** + * GStaticPrivate: + * + * A #GStaticPrivate works almost like a #GPrivate, but it has one + * significant advantage. It doesn't need to be created at run-time + * like a #GPrivate, but can be defined at compile-time. This is + * similar to the difference between #GMutex and #GStaticMutex. Now + * look at our give_me_next_number() example with + * #GStaticPrivate: + * + * Using GStaticPrivate for per-thread data + * int give_me_next_number () { static + * GStaticPrivate current_number_key = G_STATIC_PRIVATE_INIT; int + * *current_number = g_static_private_get (&current_number_key); if + * (!current_number) { current_number = g_new (int,1); *current_number + * = 0; g_static_private_set (&current_number_key, current_number, + * g_free); } *current_number = calc_next_number (*current_number); + * return *current_number; } + **/ + +/** + * G_STATIC_PRIVATE_INIT: + * + * Every #GStaticPrivate must be initialized with this macro, before it + * can be used. + * + * GStaticPrivate my_private = + * G_STATIC_PRIVATE_INIT; + **/ + +/** + * g_static_private_init: + * @private_key: a #GStaticPrivate to be initialized. + * + * Initializes @private_key. Alternatively you can initialize it with + * #G_STATIC_PRIVATE_INIT. + **/ void g_static_private_init (GStaticPrivate *private_key) { private_key->index = 0; } +/** + * g_static_private_get: + * @private_key: a #GStaticPrivate. + * @Returns: the corresponding pointer. + * + * Works like g_private_get() only for a #GStaticPrivate. + * + * This function works even if g_thread_init() has not yet been called. + **/ gpointer g_static_private_get (GStaticPrivate *private_key) { @@ -436,6 +1603,26 @@ g_static_private_get (GStaticPrivate *private_key) return NULL; } +/** + * g_static_private_set: + * @private_key: a #GStaticPrivate. + * @data: the new pointer. + * @notify: a function to be called with the pointer whenever the + * current thread ends or sets this pointer again. + * + * Sets the pointer keyed to @private_key for the current thread and + * the function @notify to be called with that pointer (%NULL or + * non-%NULL), whenever the pointer is set again or whenever the + * current thread ends. + * + * This function works even if g_thread_init() has not yet been called. + * If g_thread_init() is called later, the @data keyed to @private_key + * will be inherited only by the main thread, i.e. the one that called + * g_thread_init(). + * + * @notify is used quite differently from @destructor in + * g_private_new(). + **/ void g_static_private_set (GStaticPrivate *private_key, gpointer data, @@ -495,6 +1682,17 @@ g_static_private_set (GStaticPrivate *private_key, } } +/** + * g_static_private_free: + * @private_key: a #GStaticPrivate to be freed. + * + * Releases all resources allocated to @private_key. + * + * You don't have to call this functions for a #GStaticPrivate with an + * unbounded lifetime, i.e. objects declared 'static', but if you have + * a #GStaticPrivate as a member of a structure and the structure is + * freed, you should also free the #GStaticPrivate. + **/ void g_static_private_free (GStaticPrivate *private_key) { @@ -538,6 +1736,7 @@ g_static_private_free (GStaticPrivate *private_key) G_UNLOCK (g_thread); } +/* GThread Extra Functions {{{1 ------------------------------------------- */ static void g_thread_cleanup (gpointer data) { @@ -638,6 +1837,48 @@ g_thread_create_proxy (gpointer data) return NULL; } +/** + * g_thread_create_full: + * @func: a function to execute in the new thread. + * @data: an argument to supply to the new thread. + * @stack_size: a stack size for the new thread. + * @joinable: should this thread be joinable? + * @bound: should this thread be bound to a system thread? + * @priority: a priority for the thread. + * @error: return location for error. + * @Returns: the new #GThread on success. + * + * This function creates a new thread with the priority @priority. If + * the underlying thread implementation supports it, the thread gets a + * stack size of @stack_size or the default value for the current + * platform, if @stack_size is 0. + * + * If @joinable is %TRUE, you can wait for this threads termination + * calling g_thread_join(). Otherwise the thread will just disappear + * when it terminates. If @bound is %TRUE, this thread will be + * scheduled in the system scope, otherwise the implementation is free + * to do scheduling in the process scope. The first variant is more + * expensive resource-wise, but generally faster. On some systems (e.g. + * Linux) all threads are bound. + * + * The new thread executes the function @func with the argument @data. + * If the thread was created successfully, it is returned. + * + * @error can be %NULL to ignore errors, or non-%NULL to report errors. + * The error is set, if and only if the function returns %NULL. + * + * It is not guaranteed that threads with different priorities + * really behave accordingly. On some systems (e.g. Linux) there are no + * thread priorities. On other systems (e.g. Solaris) there doesn't + * seem to be different scheduling for different priorities. All in all + * try to avoid being dependent on priorities. Use + * %G_THREAD_PRIORITY_NORMAL here as a default. + * + * Only use g_thread_create_full() if you really can't use + * g_thread_create() instead. g_thread_create() does not take + * @stack_size, @bound, and @priority as arguments, as they should only + * be used in cases in which it is unavoidable. + **/ GThread* g_thread_create_full (GThreadFunc func, gpointer data, @@ -681,6 +1922,30 @@ g_thread_create_full (GThreadFunc func, return (GThread*) result; } +/** + * g_thread_exit: + * @retval: the return value of this thread. + * + * Exits the current thread. If another thread is waiting for that + * thread using g_thread_join() and the current thread is joinable, the + * waiting thread will be woken up and get @retval as the return value + * of g_thread_join(). If the current thread is not joinable, @retval + * is ignored. Calling + * + * g_thread_exit (retval); + * + * + * is equivalent to calling + * + * return retval; + * + * + * in the function @func, as given to g_thread_create(). + * + * Never call g_thread_exit() from within a thread of a + * #GThreadPool, as that will mess up the bookkeeping and lead to funny + * and unwanted results. + **/ void g_thread_exit (gpointer retval) { @@ -689,6 +1954,18 @@ g_thread_exit (gpointer retval) G_THREAD_CF (thread_exit, (void)0, ()); } +/** + * g_thread_join: + * @thread: a #GThread to be waited for. + * @Returns: the return value of the thread. + * + * Waits until @thread finishes, i.e. the function @func, as given to + * g_thread_create(), returns or g_thread_exit() is called by @thread. + * All resources of @thread including the #GThread struct are released. + * @thread must have been created with @joinable=%TRUE in + * g_thread_create(). The value returned by @func or given to + * g_thread_exit() by @thread is returned by this function. + **/ gpointer g_thread_join (GThread* thread) { @@ -732,6 +2009,19 @@ g_thread_join (GThread* thread) return retval; } +/** + * g_thread_set_priority: + * @thread: a #GThread. + * @priority: a new priority for @thread. + * + * Changes the priority of @thread to @priority. + * + * It is not guaranteed that threads with different + * priorities really behave accordingly. On some systems (e.g. Linux) + * there are no thread priorities. On other systems (e.g. Solaris) there + * doesn't seem to be different scheduling for different priorities. All + * in all try to avoid being dependent on priorities. + **/ void g_thread_set_priority (GThread* thread, GThreadPriority priority) @@ -749,6 +2039,13 @@ g_thread_set_priority (GThread* thread, (&real->system_thread, priority)); } +/** + * g_thread_self: + * @Returns: the current thread. + * + * This functions returns the #GThread corresponding to the calling + * thread. + **/ GThread* g_thread_self (void) { @@ -781,6 +2078,83 @@ g_thread_self (void) return (GThread*)thread; } +/* GStaticRWLock {{{1 ----------------------------------------------------- */ + +/** + * GStaticRWLock: + * + * The #GStaticRWLock struct represents a read-write lock. A read-write + * lock can be used for protecting data that some portions of code only + * read from, while others also write. In such situations it is + * desirable that several readers can read at once, whereas of course + * only one writer may write at a time. Take a look at the following + * example: An array with access functions + * GStaticRWLock rwlock = G_STATIC_RW_LOCK_INIT; + * GPtrArray *array; gpointer my_array_get (guint index) { gpointer + * retval = NULL; if (!array) return NULL; g_static_rw_lock_reader_lock + * (&rwlock); if (index < array->len) retval = g_ptr_array_index + * (array, index); g_static_rw_lock_reader_unlock (&rwlock); return + * retval; } void my_array_set (guint index, gpointer data) { + * g_static_rw_lock_writer_lock (&rwlock); if (!array) array = + * g_ptr_array_new (); if (index >= array->len) + * g_ptr_array_set_size (array, index+1); g_ptr_array_index (array, + * index) = data; g_static_rw_lock_writer_unlock (&rwlock); } + * + * + * This example shows an array which can be accessed by many readers + * (the my_array_get() function) simultaneously, + * whereas the writers (the my_array_set() + * function) will only be allowed once at a time and only if no readers + * currently access the array. This is because of the potentially + * dangerous resizing of the array. Using these functions is fully + * multi-thread safe now. + * + * Most of the time, writers should have precedence over readers. That + * means, for this implementation, that as soon as a writer wants to + * lock the data, no other reader is allowed to lock the data, whereas, + * of course, the readers that already have locked the data are allowed + * to finish their operation. As soon as the last reader unlocks the + * data, the writer will lock it. + * + * Even though #GStaticRWLock is not opaque, it should only be used + * with the following functions. + * + * All of the g_static_rw_lock_* functions can be + * used even if g_thread_init() has not been called. Then they do + * nothing, apart from g_static_rw_lock_*_trylock, + * which does nothing but returning %TRUE. + * + * A read-write lock has a higher overhead than a mutex. For + * example, both g_static_rw_lock_reader_lock() and + * g_static_rw_lock_reader_unlock() have to lock and unlock a + * #GStaticMutex, so it takes at least twice the time to lock and unlock + * a #GStaticRWLock that it does to lock and unlock a #GStaticMutex. So + * only data structures that are accessed by multiple readers, and which + * keep the lock for a considerable time justify a #GStaticRWLock. The + * above example most probably would fare better with a + * #GStaticMutex. + **/ + +/** + * G_STATIC_RW_LOCK_INIT: + * + * A #GStaticRWLock must be initialized with this macro before it can + * be used. This macro can used be to initialize a variable, but it + * cannot be assigned to a variable. In that case you have to use + * g_static_rw_lock_init(). + * + * GStaticRWLock my_lock = + * G_STATIC_RW_LOCK_INIT; + **/ + +/** + * g_static_rw_lock_init: + * @lock: a #GStaticRWLock to be initialized. + * + * A #GStaticRWLock must be initialized with this function before it + * can be used. Alternatively you can initialize it with + * #G_STATIC_RW_LOCK_INIT. + **/ void g_static_rw_lock_init (GStaticRWLock* lock) { @@ -808,6 +2182,22 @@ g_static_rw_lock_signal (GStaticRWLock* lock) g_cond_broadcast (lock->read_cond); } +/** + * g_static_rw_lock_reader_lock: + * @lock: a #GStaticRWLock to lock for reading. + * + * Locks @lock for reading. There may be unlimited concurrent locks for + * reading of a #GStaticRWLock at the same time. If @lock is already + * locked for writing by another thread or if another thread is already + * waiting to lock @lock for writing, this function will block until + * @lock is unlocked by the other writing thread and no other writing + * threads want to lock @lock. This lock has to be unlocked by + * g_static_rw_lock_reader_unlock(). + * + * #GStaticRWLock is not recursive. It might seem to be possible to + * recursively lock for reading, but that can result in a deadlock, due + * to writer preference. + **/ void g_static_rw_lock_reader_lock (GStaticRWLock* lock) { @@ -825,6 +2215,17 @@ g_static_rw_lock_reader_lock (GStaticRWLock* lock) g_static_mutex_unlock (&lock->mutex); } +/** + * g_static_rw_lock_reader_trylock: + * @lock: a #GStaticRWLock to lock for reading. + * @Returns: %TRUE, if @lock could be locked for reading. + * + * Tries to lock @lock for reading. If @lock is already locked for + * writing by another thread or if another thread is already waiting to + * lock @lock for writing, immediately returns %FALSE. Otherwise locks + * @lock for reading and returns %TRUE. This lock has to be unlocked by + * g_static_rw_lock_reader_unlock(). + **/ gboolean g_static_rw_lock_reader_trylock (GStaticRWLock* lock) { @@ -845,6 +2246,14 @@ g_static_rw_lock_reader_trylock (GStaticRWLock* lock) return ret_val; } +/** + * g_static_rw_lock_reader_unlock: + * @lock: a #GStaticRWLock to unlock after reading. + * + * Unlocks @lock. If a thread waits to lock @lock for writing and all + * locks for reading have been unlocked, the waiting thread is woken up + * and can lock @lock for writing. + **/ void g_static_rw_lock_reader_unlock (GStaticRWLock* lock) { @@ -860,6 +2269,18 @@ g_static_rw_lock_reader_unlock (GStaticRWLock* lock) g_static_mutex_unlock (&lock->mutex); } +/** + * g_static_rw_lock_writer_lock: + * @lock: a #GStaticRWLock to lock for writing. + * + * Locks @lock for writing. If @lock is already locked for writing or + * reading by other threads, this function will block until @lock is + * completely unlocked and then lock @lock for writing. While this + * functions waits to lock @lock, no other thread can lock @lock for + * reading. When @lock is locked for writing, no other thread can lock + * @lock (neither for reading nor writing). This lock has to be + * unlocked by g_static_rw_lock_writer_unlock(). + **/ void g_static_rw_lock_writer_lock (GStaticRWLock* lock) { @@ -877,6 +2298,16 @@ g_static_rw_lock_writer_lock (GStaticRWLock* lock) g_static_mutex_unlock (&lock->mutex); } +/** + * g_static_rw_lock_writer_trylock: + * @lock: a #GStaticRWLock to lock for writing. + * @Returns: %TRUE, if @lock could be locked for writing. + * + * Tries to lock @lock for writing. If @lock is already locked (for + * either reading or writing) by another thread, it immediately returns + * %FALSE. Otherwise it locks @lock for writing and returns %TRUE. This + * lock has to be unlocked by g_static_rw_lock_writer_unlock(). + **/ gboolean g_static_rw_lock_writer_trylock (GStaticRWLock* lock) { @@ -897,6 +2328,17 @@ g_static_rw_lock_writer_trylock (GStaticRWLock* lock) return ret_val; } +/** + * g_static_rw_lock_writer_unlock: + * @lock: a #GStaticRWLock to unlock after writing. + * + * Unlocks @lock. If a thread is waiting to lock @lock for writing and + * all locks for reading have been unlocked, the waiting thread is + * woken up and can lock @lock for writing. If no thread is waiting to + * lock @lock for writing, and some thread or threads are waiting to + * lock @lock for reading, the waiting threads are woken up and can + * lock @lock for reading. + **/ void g_static_rw_lock_writer_unlock (GStaticRWLock* lock) { @@ -911,6 +2353,17 @@ g_static_rw_lock_writer_unlock (GStaticRWLock* lock) g_static_mutex_unlock (&lock->mutex); } +/** + * g_static_rw_lock_free: + * @lock: a #GStaticRWLock to be freed. + * + * Releases all resources allocated to @lock. + * + * You don't have to call this functions for a #GStaticRWLock with an + * unbounded lifetime, i.e. objects declared 'static', but if you have + * a #GStaticRWLock as a member of a structure, and the structure is + * freed, you should also free the #GStaticRWLock. + **/ void g_static_rw_lock_free (GStaticRWLock* lock) { @@ -929,6 +2382,8 @@ g_static_rw_lock_free (GStaticRWLock* lock) g_static_mutex_free (&lock->mutex); } +/* Unsorted {{{1 ---------------------------------------------------------- */ + /** * g_thread_foreach * @thread_func: function to call for all GThread structures @@ -992,3 +2447,4 @@ g_thread_get_initialized () #define __G_THREAD_C__ #include "galiasdef.c" +