Attachment 86366 Details for Bug 69711 – 0005-mainloop-avoid-race-y-double-wakeup-status.patch

0005-mainloop-avoid-race-y-double-wakeup-status.patch

0005-mainloop-avoid-race-y-double-wakeup-status.patch (text/plain), 1.72 KB, created by Pierre Ossman on 2013-09-23 13:12:41 UTC

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Creator: Pierre Ossman

Created: 2013-09-23 13:12:41 UTC

Size: 1.72 KB

patch

obsolete

>From 68dd51f087a5ca70e44dd0558dad5fb935df3dc3 Mon Sep 17 00:00:00 2001
>From: Pierre Ossman <ossman@cendio.se>
>Date: Fri, 20 Sep 2013 10:26:30 +0200
>Subject: [PATCH 5/8] mainloop: avoid race-y double wakeup status
>
>Having an extra variable that tracks the wakeup status introduces a
>race where the variable is set but the data has yet to propagate from
>the write end of the pipe to the read end. When this happens the
>system goes into a tight loop as select() always returns immediately.
>---
> src/pulse/mainloop.c | 9 ++-------
> 1 file changed, 2 insertions(+), 7 deletions(-)
>
>diff --git a/src/pulse/mainloop.c b/src/pulse/mainloop.c
>index 60fbbb9..498ac7d 100644
>--- a/src/pulse/mainloop.c
>+++ b/src/pulse/mainloop.c
>@@ -114,7 +114,6 @@ struct pa_mainloop {
>     int retval;
>     bool quit:1;
> 
>-    pa_atomic_t wakeup_requested;
>     int wakeup_pipe[2];
>     int wakeup_pipe_type;
> 
>@@ -772,8 +771,6 @@ void pa_mainloop_wakeup(pa_mainloop *m) {
>     if (pa_write(m->wakeup_pipe[1], &c, sizeof(c), &m->wakeup_pipe_type) < 0)
>         /* Not much options for recovering from the error. Let's at least log something. */
>         pa_log("pa_write() failed while trying to wake up the mainloop: %s", pa_cstrerror(errno));
>-
>-    pa_atomic_store(&m->wakeup_requested, true);
> }
> 
> static void clear_wakeup(pa_mainloop *m) {
>@@ -781,10 +778,8 @@ static void clear_wakeup(pa_mainloop *m) {
> 
>     pa_assert(m);
> 
>-    if (pa_atomic_cmpxchg(&m->wakeup_requested, true, false)) {
>-        while (pa_read(m->wakeup_pipe[0], &c, sizeof(c), &m->wakeup_pipe_type) == sizeof(c))
>-            ;
>-    }
>+    while (pa_read(m->wakeup_pipe[0], &c, sizeof(c), &m->wakeup_pipe_type) == sizeof(c))
>+        ;
> }
> 
> int pa_mainloop_prepare(pa_mainloop *m, int timeout) {
>-- 
>1.8.3.1
>

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