glibc/fix-locking-in-_IO_cleanup.patch

Always do locking when accessing streams

	[BZ #15142]
	* include/libio.h (_IO_ftrylockfile) [_IO_MTSAVE_IO]: Define.
	* libio/genops.c (_IO_list_all_stamp): Delete.	All uses removed.
	* libio/genops.c (_IO_flush_all_lockp): Make static.  Rename
	argument to skip_locked, callers changed.  Skip files that are
	locked if skip_locked.
	(_IO_unbuffer_all): Lock files before access, but skip locked
	files.
	* libio/libioP.h (_IO_flush_all_all_lockp): Don't declare.

Index: glibc-2.26/include/libio.h
===================================================================
--- glibc-2.26.orig/include/libio.h
+++ glibc-2.26/include/libio.h
@@ -33,11 +33,15 @@ libc_hidden_proto (_IO_vfscanf)
   if (((_fp)->_flags & _IO_USER_LOCK) == 0) _IO_lock_lock (*(_fp)->_lock)
 #  define _IO_funlockfile(_fp) \
   if (((_fp)->_flags & _IO_USER_LOCK) == 0) _IO_lock_unlock (*(_fp)->_lock)
+#  define _IO_ftrylockfile(_fp) \
+  (((_fp)->_flags & _IO_USER_LOCK) == 0 ? _IO_lock_trylock (*(_fp)->_lock) : 0)
 # else
 #  define _IO_flockfile(_fp) \
   if (((_fp)->_flags & _IO_USER_LOCK) == 0) _IO_flockfile (_fp)
 #  define _IO_funlockfile(_fp) \
   if (((_fp)->_flags & _IO_USER_LOCK) == 0) _IO_funlockfile (_fp)
+#  define _IO_ftrylockfile(_fp) \
+  (((_fp)->_flags & _IO_USER_LOCK) == 0 ? _IO_ftrylockfile (_fp) : 0)
 # endif
 #endif /* _IO_MTSAFE_IO */
 
Index: glibc-2.26/libio/genops.c
===================================================================
--- glibc-2.26.orig/libio/genops.c
+++ glibc-2.26/libio/genops.c
@@ -38,10 +38,6 @@
 static _IO_lock_t list_all_lock = _IO_lock_initializer;
 #endif
 
-/* Used to signal modifications to the list of FILE decriptors.  */
-static int _IO_list_all_stamp;
-
-
 static _IO_FILE *run_fp;
 
 #ifdef _IO_MTSAFE_IO
@@ -69,16 +65,12 @@ _IO_un_link (struct _IO_FILE_plus *fp)
       if (_IO_list_all == NULL)
 	;
       else if (fp == _IO_list_all)
-	{
-	  _IO_list_all = (struct _IO_FILE_plus *) _IO_list_all->file._chain;
-	  ++_IO_list_all_stamp;
-	}
+	_IO_list_all = (struct _IO_FILE_plus *) _IO_list_all->file._chain;
       else
 	for (f = &_IO_list_all->file._chain; *f; f = &(*f)->_chain)
 	  if (*f == (_IO_FILE *) fp)
 	    {
 	      *f = fp->file._chain;
-	      ++_IO_list_all_stamp;
 	      break;
 	    }
       fp->file._flags &= ~_IO_LINKED;
@@ -106,7 +98,6 @@ _IO_link_in (struct _IO_FILE_plus *fp)
 #endif
       fp->file._chain = (_IO_FILE *) _IO_list_all;
       _IO_list_all = fp;
-      ++_IO_list_all_stamp;
 #ifdef _IO_MTSAFE_IO
       _IO_funlockfile ((_IO_FILE *) fp);
       run_fp = NULL;
@@ -789,25 +780,30 @@ _IO_get_column (_IO_FILE *fp)
 #endif
 
 
-int
-_IO_flush_all_lockp (int do_lock)
+static int
+_IO_flush_all_lockp (bool skip_locked)
 {
   int result = 0;
   struct _IO_FILE *fp;
-  int last_stamp;
 
 #ifdef _IO_MTSAFE_IO
-  __libc_cleanup_region_start (do_lock, flush_cleanup, NULL);
-  if (do_lock)
-    _IO_lock_lock (list_all_lock);
+  _IO_cleanup_region_start_noarg (flush_cleanup);
+  _IO_lock_lock (list_all_lock);
 #endif
 
-  last_stamp = _IO_list_all_stamp;
-  fp = (_IO_FILE *) _IO_list_all;
-  while (fp != NULL)
+  for (fp = (_IO_FILE *) _IO_list_all; fp != NULL; fp = fp->_chain)
     {
       run_fp = fp;
-      if (do_lock)
+      if (skip_locked)
+	{
+	  /* Skip files that are currently locked.  */
+	  if (_IO_ftrylockfile (fp))
+	    {
+	      run_fp = NULL;
+	      continue;
+	    }
+	}
+      else
 	_IO_flockfile (fp);
 
       if (((fp->_mode <= 0 && fp->_IO_write_ptr > fp->_IO_write_base)
@@ -820,24 +816,13 @@ _IO_flush_all_lockp (int do_lock)
 	  && _IO_OVERFLOW (fp, EOF) == EOF)
 	result = EOF;
 
-      if (do_lock)
-	_IO_funlockfile (fp);
+      _IO_funlockfile (fp);
       run_fp = NULL;
-
-      if (last_stamp != _IO_list_all_stamp)
-	{
-	  /* Something was added to the list.  Start all over again.  */
-	  fp = (_IO_FILE *) _IO_list_all;
-	  last_stamp = _IO_list_all_stamp;
-	}
-      else
-	fp = fp->_chain;
     }
 
 #ifdef _IO_MTSAFE_IO
-  if (do_lock)
-    _IO_lock_unlock (list_all_lock);
-  __libc_cleanup_region_end (0);
+  _IO_lock_unlock (list_all_lock);
+  _IO_cleanup_region_end (0);
 #endif
 
   return result;
@@ -848,7 +833,7 @@ int
 _IO_flush_all (void)
 {
   /* We want locking.  */
-  return _IO_flush_all_lockp (1);
+  return _IO_flush_all_lockp (false);
 }
 libc_hidden_def (_IO_flush_all)
 
@@ -856,16 +841,13 @@ void
 _IO_flush_all_linebuffered (void)
 {
   struct _IO_FILE *fp;
-  int last_stamp;
 
 #ifdef _IO_MTSAFE_IO
   _IO_cleanup_region_start_noarg (flush_cleanup);
   _IO_lock_lock (list_all_lock);
 #endif
 
-  last_stamp = _IO_list_all_stamp;
-  fp = (_IO_FILE *) _IO_list_all;
-  while (fp != NULL)
+  for (fp = (_IO_FILE *) _IO_list_all; fp != NULL; fp = fp->_chain)
     {
       run_fp = fp;
       _IO_flockfile (fp);
@@ -875,15 +857,6 @@ _IO_flush_all_linebuffered (void)
 
       _IO_funlockfile (fp);
       run_fp = NULL;
-
-      if (last_stamp != _IO_list_all_stamp)
-	{
-	  /* Something was added to the list.  Start all over again.  */
-	  fp = (_IO_FILE *) _IO_list_all;
-	  last_stamp = _IO_list_all_stamp;
-	}
-      else
-	fp = fp->_chain;
     }
 
 #ifdef _IO_MTSAFE_IO
@@ -919,24 +892,26 @@ static void
 _IO_unbuffer_all (void)
 {
   struct _IO_FILE *fp;
+
+#ifdef _IO_MTSAFE_IO
+  _IO_cleanup_region_start_noarg (flush_cleanup);
+  _IO_lock_lock (list_all_lock);
+#endif
+
   for (fp = (_IO_FILE *) _IO_list_all; fp; fp = fp->_chain)
     {
+      run_fp = fp;
+      /* Skip files that are currently locked.  */
+      if (_IO_ftrylockfile (fp))
+	{
+	  run_fp = NULL;
+	  continue;
+	}
+
       if (! (fp->_flags & _IO_UNBUFFERED)
 	  /* Iff stream is un-orientated, it wasn't used. */
 	  && fp->_mode != 0)
 	{
-#ifdef _IO_MTSAFE_IO
-	  int cnt;
-#define MAXTRIES 2
-	  for (cnt = 0; cnt < MAXTRIES; ++cnt)
-	    if (fp->_lock == NULL || _IO_lock_trylock (*fp->_lock) == 0)
-	      break;
-	    else
-	      /* Give the other thread time to finish up its use of the
-		 stream.  */
-	      __sched_yield ();
-#endif
-
 	  if (! dealloc_buffers && !(fp->_flags & _IO_USER_BUF))
 	    {
 	      fp->_flags |= _IO_USER_BUF;
@@ -950,17 +925,20 @@ _IO_unbuffer_all (void)
 
 	  if (fp->_mode > 0)
 	    _IO_wsetb (fp, NULL, NULL, 0);
-
-#ifdef _IO_MTSAFE_IO
-	  if (cnt < MAXTRIES && fp->_lock != NULL)
-	    _IO_lock_unlock (*fp->_lock);
-#endif
 	}
 
       /* Make sure that never again the wide char functions can be
 	 used.  */
       fp->_mode = -1;
+
+      _IO_funlockfile (fp);
+      run_fp = NULL;
     }
+
+#ifdef _IO_MTSAFE_IO
+  _IO_lock_unlock (list_all_lock);
+  _IO_cleanup_region_end (0);
+#endif
 }
 
 
@@ -980,9 +958,9 @@ libc_freeres_fn (buffer_free)
 int
 _IO_cleanup (void)
 {
-  /* We do *not* want locking.  Some threads might use streams but
-     that is their problem, we flush them underneath them.  */
-  int result = _IO_flush_all_lockp (0);
+  /* We want to skip locked streams.  Some threads might use streams but
+     that is their problem, we don't flush those.  */
+  int result = _IO_flush_all_lockp (true);
 
   /* We currently don't have a reliable mechanism for making sure that
      C++ static destructors are executed in the correct order.
Index: glibc-2.26/libio/libioP.h
===================================================================
--- glibc-2.26.orig/libio/libioP.h
+++ glibc-2.26/libio/libioP.h
@@ -507,7 +507,6 @@ extern int _IO_new_do_write (_IO_FILE *,
 extern int _IO_old_do_write (_IO_FILE *, const char *, _IO_size_t);
 extern int _IO_wdo_write (_IO_FILE *, const wchar_t *, _IO_size_t);
 libc_hidden_proto (_IO_wdo_write)
-extern int _IO_flush_all_lockp (int);
 extern int _IO_flush_all (void);
 libc_hidden_proto (_IO_flush_all)
 extern int _IO_cleanup (void);