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This patch fixes both sem_wait and sem_timedwait cancellation point for
uncontended case. In this scenario only atomics are involved and thus
the futex cancellable call is not issue and a pending cancellation signal
is not handled.
The fix is straighforward by calling pthread_testcancel is both function
start. Although it would be simpler to call CANCELLATION_P directly, I
decided to add an internal pthread_testcancel alias and use it to export
less internal implementation on such function. A possible change on
how pthread_testcancel is internally implemented would lead to either
continue to force use CANCELLATION_P or to adjust its every use.
GLIBC testcase also does have tests for uncontended cases, test-cancel12
and test-cancel14.c, however both are flawed by adding another
cancellation point just after thread pthread_cleanup_pop:
47 static void *
48 tf (void *arg)
49 {
50 pthread_cleanup_push (cleanup, NULL);
51
52 int e = pthread_barrier_wait (&bar);
53 if (e != 0 && e != PTHREAD_BARRIER_SERIAL_THREAD)
54 {
55 puts ("tf: 1st barrier_wait failed");
56 exit (1);
57 }
58
59 /* This call should block and be cancelable. */
60 sem_wait (&sem);
61
62 pthread_cleanup_pop (0);
63
64 puts ("sem_wait returned");
65
66 return NULL;
67 }
So sem_{timed}wait does not act on cancellation, pthread_cleanup_pop executes
'cleanup' and then 'puts' acts on cancellation. Since pthread_cleanup_pop
removed the clean-up handler, it will ran only once and thus it won't accuse
an error to indicate sem_wait has not acted on the cancellation signal.
This patch also fixes this behavior by removing the cancellation point 'puts'.
It also adds some cleanup on all sem_{timed}wait cancel tests.
It partially fixes BZ #18243. Checked on x86_64.
[BZ #18243]
* nptl/pthreadP.h (__pthread_testcancel): Add prototype and hidden_proto.
* nptl/pthread_testcancel.c (pthread_cancel): Add internal aliais
definition.
* nptl/sem_timedwait.c (sem_timedwait): Add cancellation check for
uncontended case.
* nptl/sem_wait.c (__new_sem_wait): Likewise.
* nptl/tst-cancel12.c (cleanup): Remove wrong cancellation point.
(tf): Fix check for uncontended case.
(do_test): Likewise.
* nptl/tst-cancel13.c (cleanup): Remove wrong cancellation point.
(tf): Fix check for uncontended case.
(do_test): Likewise.
* nptl/tst-cancel14.c (cleanup): Remove wrong cancellation point.
(tf): Fix check for uncontended case.
(do_test): Likewise.
* nptl/tst-cancel15.c (cleanup): Remove wrong cancellation point.
(tf): Fix check for uncontended case.
(do_test): Likewise.
128 lines
2.7 KiB
C
128 lines
2.7 KiB
C
/* Test sem_wait cancellation for contended case.
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Copyright (C) 2003-2016 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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Contributed by Ulrich Drepper <drepper@redhat.com>, 2003.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<http://www.gnu.org/licenses/>. */
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#include <errno.h>
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#include <pthread.h>
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#include <semaphore.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <unistd.h>
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static pthread_barrier_t bar;
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static sem_t sem;
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static void
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cleanup (void *arg)
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{
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static int ncall;
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if (++ncall != 1)
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{
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puts ("second call to cleanup");
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exit (1);
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}
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}
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static void *
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tf (void *arg)
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{
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pthread_cleanup_push (cleanup, NULL);
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int e = pthread_barrier_wait (&bar);
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if (e != 0 && e != PTHREAD_BARRIER_SERIAL_THREAD)
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{
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puts ("error: tf: 1st barrier_wait failed");
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exit (1);
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}
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/* This call should block and be cancelable. */
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sem_wait (&sem);
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pthread_cleanup_pop (0);
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return NULL;
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}
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static int
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do_test (void)
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{
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pthread_t th;
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if (pthread_barrier_init (&bar, NULL, 2) != 0)
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{
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puts ("error: barrier_init failed");
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exit (1);
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}
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/* A value equal to 0 will check for contended pthread cancellation,
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where the sem_wait operation will block. */
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if (sem_init (&sem, 0, 0) != 0)
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{
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puts ("error: sem_init failed");
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exit (1);
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}
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if (pthread_create (&th, NULL, tf, NULL) != 0)
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{
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puts ("error: create failed");
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exit (1);
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}
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int e = pthread_barrier_wait (&bar);
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if (e != 0 && e != PTHREAD_BARRIER_SERIAL_THREAD)
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{
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puts ("error: 1st barrier_wait failed");
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exit (1);
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}
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/* Give the child a chance to go to sleep in sem_wait. */
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sleep (1);
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/* Check whether cancellation is honored when waiting in sem_wait. */
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if (pthread_cancel (th) != 0)
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{
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puts ("error: 1st cancel failed");
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exit (1);
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}
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void *r;
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if (pthread_join (th, &r) != 0)
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{
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puts ("error: join failed");
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exit (1);
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}
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if (r != PTHREAD_CANCELED)
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{
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puts ("thread not canceled");
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exit (1);
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}
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return 0;
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}
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#define TEST_FUNCTION do_test ()
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#include "../test-skeleton.c"
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