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From: Eli Zaretskii <eliz@gnu.org>
To: dick.r.chiang@gmail.com
Cc: 36609@debbugs.gnu.org
Subject: bug#36609: 27.0.50; Possible race-condition in threading implementation
Date: Sun, 20 Jun 2021 14:39:31 +0300	[thread overview]
Message-ID: <837diovk7g.fsf@gnu.org> (raw)
In-Reply-To: <87o8c1wocf.fsf@dick> (dick.r.chiang@gmail.com)

> From: dick.r.chiang@gmail.com
> Cc: 36609@debbugs.gnu.org
> Date: Sat, 19 Jun 2021 17:12:32 -0400
> 
> "Suggest" or "Provide"?
> 
> If the former, well, my recalcitrance should be your answer.
> 
> If the latter, sure

Thanks, please try the patch below.

> although if you've written the patch, then running my MREs would be
> epsilon more effort.

You have a use case and wrote code with which you are familiar, so you
are in a better position to test it.  Moreover, I don't have access to
a system where these problems could happen, so it's far from epsilon
effort for me.

diff --git a/src/xgselect.c b/src/xgselect.c
index 0d91d55bad..9a90670b0f 100644
--- a/src/xgselect.c
+++ b/src/xgselect.c
@@ -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))
+    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?





  reply	other threads:[~2021-06-20 11:39 UTC|newest]

Thread overview: 53+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-07-11 20:51 bug#36609: 27.0.50; Possible race-condition in threading implementation Andreas Politz
2019-07-12  7:47 ` Eli Zaretskii
2019-07-12  8:05   ` Eli Zaretskii
2019-07-12  9:02 ` Pip Cet
2019-07-12 12:42   ` Eli Zaretskii
2019-07-12 12:57     ` Pip Cet
2019-07-12 13:31       ` Eli Zaretskii
2019-07-12 13:51         ` Pip Cet
2019-07-12 15:05           ` Eli Zaretskii
2019-07-12 18:06             ` Pip Cet
2019-07-12 18:27               ` Eli Zaretskii
2019-07-12 18:34                 ` Eli Zaretskii
2019-07-12 19:24                   ` Pip Cet
2019-07-12 19:57                     ` Eli Zaretskii
2019-07-13 14:37                       ` Pip Cet
2019-07-13 15:03                         ` Eli Zaretskii
2019-07-13 15:13                           ` Eli Zaretskii
2019-07-13 15:54                           ` Eli Zaretskii
2019-07-13 15:57                             ` Pip Cet
2019-07-13 16:02                               ` Eli Zaretskii
2019-07-13 18:17                                 ` Pip Cet
2020-08-21 12:57                                   ` Lars Ingebrigtsen
2019-07-13 15:04                         ` Andreas Politz
2019-07-12 12:44   ` Pip Cet
2019-07-12 12:55     ` Eli Zaretskii
2019-07-12 13:40       ` Pip Cet
2019-07-12 13:51         ` Eli Zaretskii
2019-07-12 14:34           ` Pip Cet
2019-07-12 15:02             ` Eli Zaretskii
2019-07-12 19:30               ` Pip Cet
2019-07-13  6:50                 ` Eli Zaretskii
2021-06-06 15:50 ` dick.r.chiang
     [not found] ` <87fsxv8182.fsf@dick>
2021-06-06 16:35   ` Eli Zaretskii
2021-06-06 19:10     ` dick.r.chiang
2021-06-06 19:27       ` Eli Zaretskii
2021-06-09 21:40         ` dick.r.chiang
2021-06-10  6:46           ` Eli Zaretskii
2021-06-10 11:52             ` dick.r.chiang
2021-06-10 14:18               ` Eli Zaretskii
2021-06-10 14:55                 ` dick.r.chiang
2021-06-10 15:04                   ` Eli Zaretskii
2021-06-10 21:36                     ` dick.r.chiang
2021-06-11  6:00                       ` Eli Zaretskii
2021-06-19 17:53                         ` Eli Zaretskii
2021-06-19 19:14                           ` dick.r.chiang
2021-06-19 19:18                             ` Eli Zaretskii
2021-06-19 21:12                               ` dick.r.chiang
2021-06-20 11:39                                 ` Eli Zaretskii [this message]
2021-06-20 14:01                                   ` dick.r.chiang
2021-06-20 15:53                                     ` Eli Zaretskii
2021-06-25 13:54                                       ` Eli Zaretskii
2021-06-10 15:35                 ` Andreas Schwab
2021-06-10 15:39                   ` Eli Zaretskii

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