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Fix a possible deadlock

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the FdSource was calling g_cancellable_disconnect while holding the
main context lock, which is bad news if the ::cancelled handler is
trying to get that lock to wake up the mainloop...

Bug 586432
This commit is contained in:
Matthias Clasen
2010-08-03 10:41:21 -04:00
parent 5179d92e9c
commit b2715bbc5e
2 changed files with 7 additions and 23 deletions
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6
gio/gasynchelper.c
View File

@@ -86,8 +86,12 @@ fd_source_finalize (GSource *source)
{ {
FDSource *fd_source = (FDSource *)source; FDSource *fd_source = (FDSource *)source;
/* we don't use g_cancellable_disconnect() here, since we are holding
* the main context lock here, and the ::disconnect signal handler
* will try to grab that, and deadlock looms.
*/
if (fd_source->cancelled_tag) if (fd_source->cancelled_tag)
g_cancellable_disconnect (fd_source->cancellable, g_signal_handler_disconnect (fd_source->cancellable,
fd_source->cancelled_tag); fd_source->cancelled_tag);
if (fd_source->cancellable) if (fd_source->cancellable)

22
gio/tests/unix-streams.c
View File

@@ -33,16 +33,6 @@ int writer_pipe[2], reader_pipe[2];
GCancellable *writer_cancel, *reader_cancel, *main_cancel; GCancellable *writer_cancel, *reader_cancel, *main_cancel;
GMainLoop *loop; GMainLoop *loop;
static gboolean
cancel_main (gpointer data)
{
GCancellable *main_cancel = data;
g_cancellable_cancel (main_cancel);
return FALSE;
}
static gpointer static gpointer
writer_thread (gpointer user_data) writer_thread (gpointer user_data)
@@ -74,17 +64,7 @@ writer_thread (gpointer user_data)
if (g_cancellable_is_cancelled (writer_cancel)) if (g_cancellable_is_cancelled (writer_cancel))
{ {
/* FIXME: directly calling g_cancellable_cancel (main_cancel) here g_cancellable_cancel (main_cancel);
* leads to sporadic deadlock, because it will try to wake up the
* main context, for which it needs to acquire the main context lock.
* This lock may be held by the main loop running in the main thread,
* and it may be held while the main thread is blocking in
* fd_source_finalize -> g_cancellable_disconnect
* until the ::cancelled callbacks have run.
*
* Work around by deferring the cancellation to a timeout.
*/
g_timeout_add (0, cancel_main, main_cancel);
g_object_unref (out); g_object_unref (out);
return NULL; return NULL;
} }