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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
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@@ -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);