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Fix sem_post race (bug 14532).

This commit is contained in:
Joseph Myers 2012-08-31 19:49:31 +00:00
parent d22e28b070
commit 033d54a2d4
5 changed files with 101 additions and 6 deletions
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2
NEWS
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@ -12,7 +12,7 @@ Version 2.17
3479, 5400, 6778, 6808, 9685, 11607, 13717, 13696, 13939, 14042, 14090,
14166, 14150, 14151, 14154, 14157, 14166, 14173, 14195, 14252, 14283,
14298, 14303, 14307, 14328, 14331, 14336, 14337, 14347, 14349, 14459,
14476, 14505, 14516, 14519
14476, 14505, 14516, 14519, 14532
* Support for STT_GNU_IFUNC symbols added for s390 and s390x.
Optimized versions of memcpy, memset, and memcmp added for System z10 and

8
nptl/ChangeLog
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@ -1,6 +1,10 @@
2012-08-15 Roland McGrath <roland@hack.frob.com>
2012-08-31 Joseph Myers <joseph@codesourcery.com>
2012-08-15 Roland McGrath <roland@hack.frob.com>
[BZ #14532]
* sysdeps/unix/sysv/linux/sem_post.c (__new_sem_post): Use
atomic_compare_and_exchange_bool_rel.
* tst-sem14.c: New file.
* Makefile (tests): Add tst-sem14.
2012-08-15 Roland McGrath <roland@hack.frob.com>

2
nptl/Makefile
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@ -217,7 +217,7 @@ tests = tst-typesizes \
tst-once1 tst-once2 tst-once3 tst-once4 \
tst-key1 tst-key2 tst-key3 tst-key4 \
tst-sem1 tst-sem2 tst-sem3 tst-sem4 tst-sem5 tst-sem6 tst-sem7 \
tst-sem8 tst-sem9 tst-sem10 tst-sem11 tst-sem12 tst-sem13 \
tst-sem8 tst-sem9 tst-sem10 tst-sem11 tst-sem12 tst-sem13 tst-sem14 \
tst-barrier1 tst-barrier2 tst-barrier3 tst-barrier4 \
tst-align tst-align2 tst-align3 \
tst-basic1 tst-basic2 tst-basic3 tst-basic4 tst-basic5 tst-basic6 \

4
nptl/sysdeps/unix/sysv/linux/sem_post.c
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@ -1,5 +1,5 @@
/* sem_post -- post to a POSIX semaphore. Generic futex-using version.
Copyright (C) 2003, 2004, 2007, 2008 Free Software Foundation, Inc.
Copyright (C) 2003-2012 Free Software Foundation, Inc.
This file is part of the GNU C Library.
Contributed by Jakub Jelinek <jakub@redhat.com>, 2003.
@ -40,7 +40,7 @@ __new_sem_post (sem_t *sem)
return -1;
}
}
while (atomic_compare_and_exchange_bool_acq (&isem->value, cur + 1, cur));
while (atomic_compare_and_exchange_bool_rel (&isem->value, cur + 1, cur));
atomic_full_barrier ();
if (isem->nwaiters > 0)

91
nptl/tst-sem14.c Normal file
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@ -0,0 +1,91 @@
/* Test for sem_post race: bug 14532.
Copyright (C) 2012 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<http://www.gnu.org/licenses/>. */
#include <pthread.h>
#include <semaphore.h>
#include <stdio.h>
#define NTHREADS 10
#define NITER 100000
sem_t sem;
int c;
volatile int thread_fail;
static void *
tf (void *arg)
{
for (int i = 0; i < NITER; i++)
{
if (sem_wait (&sem) != 0)
{
perror ("sem_wait");
thread_fail = 1;
}
++c;
if (sem_post (&sem) != 0)
{
perror ("sem_post");
thread_fail = 1;
}
}
return NULL;
}
static int
do_test (void)
{
if (sem_init (&sem, 0, 0) != 0)
{
perror ("sem_init");
return 1;
}
pthread_t th[NTHREADS];
for (int i = 0; i < NTHREADS; i++)
{
if (pthread_create (&th[i], NULL, tf, NULL) != 0)
{
puts ("pthread_create failed");
return 1;
}
}
if (sem_post (&sem) != 0)
{
perror ("sem_post");
return 1;
}
for (int i = 0; i < NTHREADS; i++)
if (pthread_join (th[i], NULL) != 0)
{
puts ("pthread_join failed");
return 1;
}
if (c != NTHREADS * NITER)
{
printf ("c = %d, should be %d\n", c, NTHREADS * NITER);
return 1;
}
return thread_fail;
}
#define TEST_FUNCTION do_test ()
#include "../test-skeleton.c"