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gtask: don't deadlock when tasks block on other tasks

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If tasks block waiting for other tasks to complete then the system can
end up starved for threads. Avoid this by bumping up max-threads in
that case.

This also reverts 7b1f8c58 and reverts max-threads for GTask's
GThreadPool back to 10.

https://bugzilla.gnome.org/show_bug.cgi?id=687223
This commit is contained in:
Dan Winship 2012-12-15 11:44:59 -05:00
parent 2149b29468
commit 07bb8097e5
2 changed files with 114 additions and 10 deletions
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41
gio/gtask.c
View File

@ -584,6 +584,7 @@ struct _GTask {
gboolean thread_cancelled;
gboolean synchronous;
gboolean thread_complete;
gboolean blocking_other_task;
GError *error;
union {
@ -613,6 +614,8 @@ G_DEFINE_TYPE_WITH_CODE (GTask, g_task, G_TYPE_OBJECT,
g_task_thread_pool_init ();)
static GThreadPool *task_pool;
static GMutex task_pool_mutex;
static GPrivate task_private = G_PRIVATE_INIT (NULL);
static void
g_task_init (GTask *task)
@ -1208,6 +1211,15 @@ g_task_thread_complete (GTask *task)
}
task->thread_complete = TRUE;
if (task->blocking_other_task)
{
g_mutex_lock (&task_pool_mutex);
g_thread_pool_set_max_threads (task_pool,
g_thread_pool_get_max_threads (task_pool) - 1,
NULL);
g_mutex_unlock (&task_pool_mutex);
}
g_mutex_unlock (&task->lock);
if (task->cancellable)
@ -1225,9 +1237,13 @@ g_task_thread_pool_thread (gpointer thread_data,
{
GTask *task = thread_data;
g_private_set (&task_private, task);
task->task_func (task, task->source_object, task->task_data,
task->cancellable);
g_task_thread_complete (task);
g_private_set (&task_private, NULL);
g_object_unref (task);
}
@ -1294,6 +1310,18 @@ g_task_start_task_thread (GTask *task,
g_thread_pool_push (task_pool, g_object_ref (task), &task->error);
if (task->error)
task->thread_complete = TRUE;
else if (g_private_get (&task_private))
{
/* This thread is being spawned from another GTask thread, so
* bump up max-threads so we don't starve.
*/
g_mutex_lock (&task_pool_mutex);
if (g_thread_pool_set_max_threads (task_pool,
g_thread_pool_get_max_threads (task_pool) + 1,
NULL))
task->blocking_other_task = TRUE;
g_mutex_unlock (&task_pool_mutex);
}
}
/**
@ -1747,12 +1775,19 @@ g_task_compare_priority (gconstpointer a,
const GTask *tb = b;
gboolean a_cancelled, b_cancelled;
/* Tasks that are causing other tasks to block have higher
* priority.
*/
if (ta->blocking_other_task && !tb->blocking_other_task)
return -1;
else if (tb->blocking_other_task && !ta->blocking_other_task)
return 1;
/* Let already-cancelled tasks finish right away */
a_cancelled = (ta->check_cancellable &&
g_cancellable_is_cancelled (ta->cancellable));
b_cancelled = (tb->check_cancellable &&
g_cancellable_is_cancelled (tb->cancellable));
/* Let already-cancelled tasks finish right away */
if (a_cancelled && !b_cancelled)
return -1;
else if (b_cancelled && !a_cancelled)
@ -1766,7 +1801,7 @@ static void
g_task_thread_pool_init (void)
{
task_pool = g_thread_pool_new (g_task_thread_pool_thread, NULL,
100, FALSE, NULL);
10, FALSE, NULL);
g_assert (task_pool != NULL);
g_thread_pool_set_sort_function (task_pool, g_task_compare_priority, NULL);

83
gio/tests/task.c
View File

@ -824,29 +824,37 @@ fake_task_thread (GTask *task,
g_task_return_boolean (task, TRUE);
}
#define G_TASK_THREAD_POOL_SIZE 100
#define G_TASK_THREAD_POOL_SIZE 10
static int fake_tasks_running;
static void
test_run_in_thread_priority (void)
fake_task_callback (GObject *source,
GAsyncResult *result,
gpointer user_data)
{
if (--fake_tasks_running == 0)
g_main_loop_quit (loop);
}
static void
clog_up_thread_pool (void)
{
GTask *task;
GCancellable *cancellable;
int seq_a, seq_b, seq_c, seq_d;
int i;
/* Flush the thread pool, then clog it up with junk tasks */
g_thread_pool_stop_unused_threads ();
g_mutex_lock (&fake_task_mutex);
for (i = 0; i < G_TASK_THREAD_POOL_SIZE - 1; i++)
{
task = g_task_new (NULL, NULL, NULL, NULL);
task = g_task_new (NULL, NULL, fake_task_callback, NULL);
g_task_set_task_data (task, &fake_task_mutex, NULL);
g_assert_cmpint (g_task_get_priority (task), ==, G_PRIORITY_DEFAULT);
g_task_set_priority (task, G_PRIORITY_HIGH * 2);
g_assert_cmpint (g_task_get_priority (task), ==, G_PRIORITY_HIGH * 2);
g_task_run_in_thread (task, fake_task_thread);
g_object_unref (task);
fake_tasks_running++;
}
g_mutex_lock (&last_fake_task_mutex);
@ -855,6 +863,23 @@ test_run_in_thread_priority (void)
g_task_set_priority (task, G_PRIORITY_HIGH * 2);
g_task_run_in_thread (task, fake_task_thread);
g_object_unref (task);
}
static void
unclog_thread_pool (void)
{
g_mutex_unlock (&fake_task_mutex);
g_main_loop_run (loop);
}
static void
test_run_in_thread_priority (void)
{
GTask *task;
GCancellable *cancellable;
int seq_a, seq_b, seq_c, seq_d;
clog_up_thread_pool ();
/* Queue three more tasks that we'll arrange to have run serially */
task = g_task_new (NULL, NULL, NULL, NULL);
@ -894,7 +919,50 @@ test_run_in_thread_priority (void)
g_assert_cmpint (seq_a, ==, 3);
g_assert_cmpint (seq_b, ==, 4);
g_mutex_unlock (&fake_task_mutex);
unclog_thread_pool ();
}
/* test_run_in_thread_nested: task threads that block waiting on
* other task threads will not cause the thread pool to starve.
*/
static void
run_nested_task_thread (GTask *task,
gpointer source_object,
gpointer task_data,
GCancellable *cancellable)
{
GTask *nested;
int *nested_tasks_left = task_data;
if ((*nested_tasks_left)--)
{
nested = g_task_new (NULL, NULL, NULL, NULL);
g_task_set_task_data (nested, nested_tasks_left, NULL);
g_task_run_in_thread_sync (nested, run_nested_task_thread);
g_object_unref (nested);
}
g_task_return_boolean (task, TRUE);
}
static void
test_run_in_thread_nested (void)
{
GTask *task;
int nested_tasks_left = 2;
clog_up_thread_pool ();
task = g_task_new (NULL, NULL, quit_main_loop_callback, NULL);
g_task_set_task_data (task, &nested_tasks_left, NULL);
g_task_run_in_thread (task, run_nested_task_thread);
g_object_unref (task);
g_mutex_unlock (&last_fake_task_mutex);
g_main_loop_run (loop);
unclog_thread_pool ();
}
/* test_return_on_cancel */
@ -1652,6 +1720,7 @@ main (int argc, char **argv)
g_test_add_func ("/gtask/run-in-thread", test_run_in_thread);
g_test_add_func ("/gtask/run-in-thread-sync", test_run_in_thread_sync);
g_test_add_func ("/gtask/run-in-thread-priority", test_run_in_thread_priority);
g_test_add_func ("/gtask/run-in-thread-nested", test_run_in_thread_nested);
g_test_add_func ("/gtask/return-on-cancel", test_return_on_cancel);
g_test_add_func ("/gtask/return-on-cancel-sync", test_return_on_cancel_sync);
g_test_add_func ("/gtask/return-on-cancel-atomic", test_return_on_cancel_atomic);