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glib-unix: fix handling of multiple signal source for the same signal

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We can't reset the pending flag for a signal until we've traversed
the whole list, as the documentation clearly says that in case multiple
sources they all get invoked.
This is still racy if you get a signal after checking the flag
but before resetting it, but it was the same before. The correct
fix would be to use sigwait() or signalfd(), but that would mean
blocking all signals in all threads, which is not compatible
with existing applications.

https://bugzilla.gnome.org/show_bug.cgi?id=704322
This commit is contained in:
Giovanni Campagna 2013-07-16 15:26:02 +02:00
parent 72a7e824d6
commit be2c7b83c4
2 changed files with 71 additions and 5 deletions
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6
glib/gmain.c
View File

@ -4828,8 +4828,6 @@ dispatch_unix_signals (void)
/* handle GChildWatchSource instances */
if (unix_signal_pending[SIGCHLD])
{
unix_signal_pending[SIGCHLD] = FALSE;
/* The only way we can do this is to scan all of the children.
*
* The docs promise that we will not reap children that we are not
@ -4875,7 +4873,6 @@ dispatch_unix_signals (void)
{
if (unix_signal_pending[source->signum])
{
unix_signal_pending[source->signum] = FALSE;
source->pending = TRUE;
wake_source ((GSource *) source);
@ -4883,6 +4880,8 @@ dispatch_unix_signals (void)
}
}
memset ((void*)unix_signal_pending, 0, sizeof (unix_signal_pending));
G_UNLOCK(unix_signal_lock);
}
@ -4994,7 +4993,6 @@ _g_main_create_unix_signal_watch (int signum)
unix_signal_watches = g_slist_prepend (unix_signal_watches, unix_signal_source);
if (unix_signal_pending[signum])
unix_signal_source->pending = TRUE;
unix_signal_pending[signum] = FALSE;
G_UNLOCK (unix_signal_lock);
return source;

70
glib/tests/unix.c
View File

@ -65,6 +65,7 @@ test_error (void)
}
static gboolean sig_received = FALSE;
static int sig_counter = 0;
static gboolean
on_sig_received (gpointer user_data)
@ -72,6 +73,7 @@ on_sig_received (gpointer user_data)
GMainLoop *loop = user_data;
g_main_loop_quit (loop);
sig_received = TRUE;
sig_counter ++;
return G_SOURCE_REMOVE;
}
@ -92,6 +94,17 @@ exit_mainloop (gpointer data)
return G_SOURCE_REMOVE;
}
static gboolean
on_sig_received_2 (gpointer data)
{
GMainLoop *loop = data;
sig_counter ++;
if (sig_counter == 2)
g_main_loop_quit (loop);
return G_SOURCE_REMOVE;
}
static void
test_signal (int signum)
{
@ -101,6 +114,7 @@ test_signal (int signum)
mainloop = g_main_loop_new (NULL, FALSE);
sig_received = FALSE;
sig_counter = 0;
g_unix_signal_add (signum, on_sig_received, mainloop);
kill (getpid (), signum);
g_assert (!sig_received);
@ -114,8 +128,19 @@ test_signal (int signum)
g_timeout_add (500, exit_mainloop, mainloop);
g_main_loop_run (mainloop);
g_assert (!sig_received);
g_main_loop_unref (mainloop);
/* Ensure that two sources for the same signal get it */
sig_counter = 0;
g_unix_signal_add (signum, on_sig_received_2, mainloop);
g_unix_signal_add (signum, on_sig_received_2, mainloop);
id = g_timeout_add (500, sig_not_received, mainloop);
kill (getpid (), signum);
g_main_loop_run (mainloop);
g_assert_cmpint (sig_counter, ==, 2);
g_source_remove (id);
g_main_loop_unref (mainloop);
}
static void
@ -147,6 +172,48 @@ test_sighup_add_remove (void)
}
static gboolean
nested_idle (gpointer data)
{
GMainLoop *parent, *nested;
GMainContext *context;
GSource *source;
context = g_main_context_new ();
nested = g_main_loop_new (context, FALSE);
source = g_unix_signal_source_new (SIGHUP);
g_source_set_callback (source, on_sig_received, nested, NULL);
g_source_attach (source, context);
kill (getpid (), SIGHUP);
g_main_loop_run (nested);
g_assert_cmpint (sig_counter, ==, 1);
g_main_loop_unref (nested);
g_main_context_unref (context);
return G_SOURCE_REMOVE;
}
static void
test_sighup_nested (void)
{
GMainLoop *mainloop;
mainloop = g_main_loop_new (NULL, FALSE);
sig_counter = 0;
sig_received = FALSE;
g_unix_signal_add (SIGHUP, on_sig_received, mainloop);
g_idle_add (nested_idle, mainloop);
g_main_loop_run (mainloop);
g_assert_cmpint (sig_counter, ==, 2);
g_main_loop_unref (mainloop);
}
int
main (int argc,
char *argv[])
@ -159,6 +226,7 @@ main (int argc,
g_test_add_func ("/glib-unix/sigterm", test_sigterm);
g_test_add_func ("/glib-unix/sighup_again", test_sighup);
g_test_add_func ("/glib-unix/sighup_add_remove", test_sighup_add_remove);
g_test_add_func ("/glib-unix/sighup_nested", test_sighup_nested);
return g_test_run();
}