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* sysdeps/unix/sysv/linux/lowlevelrobustlock.c

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(__lll_robust_lock_wait): Fix race caused by reloading of futex value.
	(__lll_robust_timedlock_wait): Likewise.
	Reported by Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>.
This commit is contained in:
Ulrich Drepper 2007-05-07 14:26:13 +00:00
parent f84ecfd74f
commit 6780bc44e8
2 changed files with 26 additions and 3 deletions
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7
nptl/ChangeLog
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@ -1,3 +1,10 @@
2007-05-07 Ulrich Drepper <drepper@redhat.com>
* sysdeps/unix/sysv/linux/lowlevelrobustlock.c
(__lll_robust_lock_wait): Fix race caused by reloading of futex value.
(__lll_robust_timedlock_wait): Likewise.
Reported by Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>.
2007-05-06 Mike Frysinger <vapier@gentoo.org> 2007-05-06 Mike Frysinger <vapier@gentoo.org>
[BZ #4465] [BZ #4465]

22
nptl/sysdeps/unix/sysv/linux/lowlevelrobustlock.c
View File

@ -1,4 +1,4 @@
/* Copyright (C) 2006 Free Software Foundation, Inc. /* Copyright (C) 2006, 2007 Free Software Foundation, Inc.
This file is part of the GNU C Library. This file is part of the GNU C Library.
Contributed by Jakub Jelinek <jakub@redhat.com>, 2006. Contributed by Jakub Jelinek <jakub@redhat.com>, 2006.
@ -30,6 +30,10 @@ __lll_robust_lock_wait (int *futex)
int oldval = *futex; int oldval = *futex;
int tid = THREAD_GETMEM (THREAD_SELF, tid); int tid = THREAD_GETMEM (THREAD_SELF, tid);
/* If the futex changed meanwhile try locking again. */
if (oldval == 0)
goto try;
do do
{ {
if (__builtin_expect (oldval & FUTEX_OWNER_DIED, 0)) if (__builtin_expect (oldval & FUTEX_OWNER_DIED, 0))
@ -41,6 +45,9 @@ __lll_robust_lock_wait (int *futex)
continue; continue;
lll_futex_wait (futex, newval); lll_futex_wait (futex, newval);
try:
;
} }
while ((oldval = atomic_compare_and_exchange_val_acq (futex, while ((oldval = atomic_compare_and_exchange_val_acq (futex,
tid | FUTEX_WAITERS, tid | FUTEX_WAITERS,
@ -57,6 +64,11 @@ __lll_robust_timedlock_wait (int *futex, const struct timespec *abstime)
return EINVAL; return EINVAL;
int tid = THREAD_GETMEM (THREAD_SELF, tid); int tid = THREAD_GETMEM (THREAD_SELF, tid);
int oldval = *futex;
/* If the futex changed meanwhile try locking again. */
if (oldval == 0)
goto try;
do do
{ {
@ -80,7 +92,6 @@ __lll_robust_timedlock_wait (int *futex, const struct timespec *abstime)
return ETIMEDOUT; return ETIMEDOUT;
/* Wait. */ /* Wait. */
int oldval = *futex;
if (__builtin_expect (oldval & FUTEX_OWNER_DIED, 0)) if (__builtin_expect (oldval & FUTEX_OWNER_DIED, 0))
return oldval; return oldval;
@ -90,8 +101,13 @@ __lll_robust_timedlock_wait (int *futex, const struct timespec *abstime)
continue; continue;
lll_futex_timed_wait (futex, newval, &rt); lll_futex_timed_wait (futex, newval, &rt);
try:
;
} }
while (atomic_compare_and_exchange_bool_acq (futex, tid | FUTEX_WAITERS, 0)); while ((oldval = atomic_compare_and_exchange_val_acq (futex,
tid | FUTEX_WAITERS,
0)) != 0);
return 0; return 0;
} }