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gthread: fix minor errno problem in GCond

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The return value from `g_cond_wait_until()` is calculated, based on the
value of `errno` after reacquiring the mutex.  This is a problem because
`errno` can be overwritten in the case the mutex is contended (in which
case the slow-path code will re-enter the kernel).

Perform the calculation before reacquiring the mutex.

See merge request GNOME/glib!958
This commit is contained in:
Allison Karlitskaya
2019-06-28 10:15:33 +02:00
parent 01bc57576b
commit d92f22ab47
1 changed files with 3 additions and 1 deletions
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4
glib/gthread-posix.c
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@@ -1441,6 +1441,7 @@ g_cond_wait_until (GCond *cond,
struct timespec span; struct timespec span;
guint sampled; guint sampled;
int res; int res;
gboolean success;
if (end_time < 0) if (end_time < 0)
return FALSE; return FALSE;
@@ -1460,9 +1461,10 @@ g_cond_wait_until (GCond *cond,
sampled = cond->i[0]; sampled = cond->i[0];
g_mutex_unlock (mutex); g_mutex_unlock (mutex);
res = syscall (__NR_futex, &cond->i[0], (gsize) FUTEX_WAIT_PRIVATE, (gsize) sampled, &span); res = syscall (__NR_futex, &cond->i[0], (gsize) FUTEX_WAIT_PRIVATE, (gsize) sampled, &span);
success = (res < 0 && errno == ETIMEDOUT) ? FALSE : TRUE;
g_mutex_lock (mutex); g_mutex_lock (mutex);
return (res < 0 && errno == ETIMEDOUT) ? FALSE : TRUE; return success;
} }
#endif #endif