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Fix race conditions between Lisp threads in GTK builds

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* src/xgselect.c (release_select_lock, acquire_select_lock)
[GCC >= 4.7.0]: Use '__atomic' builtins to prevent races between
threads in accessing 'threads_holding_glib_lock'.  Reported by
<dick.r.chiang@gmail.com>.  (Bug#36609)
This commit is contained in:
Eli Zaretskii 2021-06-25 16:52:48 +03:00
parent 2fbe17c49a
commit 6e0bff0296
1 changed files with 16 additions and 0 deletions
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16
src/xgselect.c
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@ -34,12 +34,27 @@ static GMainContext *glib_main_context;
void release_select_lock (void)
{
#if GNUC_PREREQ (4, 7, 0)
if (__atomic_sub_fetch (&threads_holding_glib_lock, 1, __ATOMIC_ACQ_REL) == 0)
g_main_context_release (glib_main_context);
#else
if (--threads_holding_glib_lock == 0)
g_main_context_release (glib_main_context);
#endif
}
static void acquire_select_lock (GMainContext *context)
{
#if GNUC_PREREQ (4, 7, 0)
if (__atomic_fetch_add (&threads_holding_glib_lock, 1, __ATOMIC_ACQ_REL) == 0)
{
glib_main_context = context;
while (!g_main_context_acquire (context))
{
/* Spin. */
}
}
#else
if (threads_holding_glib_lock++ == 0)
{
glib_main_context = context;
@ -48,6 +63,7 @@ static void acquire_select_lock (GMainContext *context)
/* Spin. */
}
}
#endif
}
/* `xg_select' is a `pselect' replacement. Why do we need a separate function?