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authorAdhemerval Zanella <adhemerval.zanella@linaro.org>2016-08-22 09:39:46 -0300
committerAdhemerval Zanella <adhemerval.zanella@linaro.org>2016-09-15 11:14:31 -0300
commit47677f2edc815e85d0383a89b09733e95e5d7302 (patch)
treee6c5db6e9cff5127be9efe1ffbd4893a3808a245 /nptl
parent49ad334ab10671dabb40eda8beba887ef902f0f3 (diff)
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nptl: Fix sem_wait and sem_timedwait cancellation (BZ#18243)
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.
Diffstat (limited to 'nptl')
-rw-r--r--nptl/pthreadP.h2
-rw-r--r--nptl/pthread_testcancel.c4
-rw-r--r--nptl/sem_timedwait.c3
-rw-r--r--nptl/sem_wait.c13
-rw-r--r--nptl/tst-cancel12.c29
-rw-r--r--nptl/tst-cancel13.c23
-rw-r--r--nptl/tst-cancel14.c17
-rw-r--r--nptl/tst-cancel15.c23
8 files changed, 62 insertions, 52 deletions
diff --git a/nptl/pthreadP.h b/nptl/pthreadP.h
index 4edc74b..6e0dd09 100644
--- a/nptl/pthreadP.h
+++ b/nptl/pthreadP.h
@@ -491,6 +491,7 @@ extern int __pthread_setcanceltype (int type, int *oldtype);
extern int __pthread_enable_asynccancel (void) attribute_hidden;
extern void __pthread_disable_asynccancel (int oldtype)
internal_function attribute_hidden;
+extern void __pthread_testcancel (void);
#if IS_IN (libpthread)
hidden_proto (__pthread_mutex_init)
@@ -505,6 +506,7 @@ hidden_proto (__pthread_getspecific)
hidden_proto (__pthread_setspecific)
hidden_proto (__pthread_once)
hidden_proto (__pthread_setcancelstate)
+hidden_proto (__pthread_testcancel)
#endif
extern int __pthread_cond_broadcast_2_0 (pthread_cond_2_0_t *cond);
diff --git a/nptl/pthread_testcancel.c b/nptl/pthread_testcancel.c
index 51be09f..fdef699 100644
--- a/nptl/pthread_testcancel.c
+++ b/nptl/pthread_testcancel.c
@@ -21,7 +21,9 @@
void
-pthread_testcancel (void)
+__pthread_testcancel (void)
{
CANCELLATION_P (THREAD_SELF);
}
+strong_alias (__pthread_testcancel, pthread_testcancel)
+hidden_def (__pthread_testcancel)
diff --git a/nptl/sem_timedwait.c b/nptl/sem_timedwait.c
index 1aab25a..a02e178 100644
--- a/nptl/sem_timedwait.c
+++ b/nptl/sem_timedwait.c
@@ -30,6 +30,9 @@ sem_timedwait (sem_t *sem, const struct timespec *abstime)
return -1;
}
+ /* Check sem_wait.c for a more detailed explanation why it is required. */
+ __pthread_testcancel ();
+
if (__new_sem_wait_fast ((struct new_sem *) sem, 0) == 0)
return 0;
else
diff --git a/nptl/sem_wait.c b/nptl/sem_wait.c
index 84b523a..b242c08 100644
--- a/nptl/sem_wait.c
+++ b/nptl/sem_wait.c
@@ -23,6 +23,19 @@
int
__new_sem_wait (sem_t *sem)
{
+ /* We need to check whether we need to act upon a cancellation request here
+ because POSIX specifies that cancellation points "shall occur" in
+ sem_wait and sem_timedwait, which also means that they need to check
+ this regardless whether they block or not (unlike "may occur"
+ functions). See the POSIX Rationale for this requirement: Section
+ "Thread Cancellation Overview" [1] and austin group issue #1076 [2]
+ for thoughs on why this may be a suboptimal design.
+
+ [1] http://pubs.opengroup.org/onlinepubs/9699919799/xrat/V4_xsh_chap02.html
+ [2] http://austingroupbugs.net/view.php?id=1076 for thoughts on why this
+ */
+ __pthread_testcancel ();
+
if (__new_sem_wait_fast ((struct new_sem *) sem, 0) == 0)
return 0;
else
diff --git a/nptl/tst-cancel12.c b/nptl/tst-cancel12.c
index ac8f5a0..a720ccf 100644
--- a/nptl/tst-cancel12.c
+++ b/nptl/tst-cancel12.c
@@ -1,4 +1,5 @@
-/* Copyright (C) 2003-2016 Free Software Foundation, Inc.
+/* Test sem_wait cancellation for uncontended case.
+ Copyright (C) 2003-2016 Free Software Foundation, Inc.
This file is part of the GNU C Library.
Contributed by Ulrich Drepper <drepper@redhat.com>, 2003.
@@ -39,8 +40,6 @@ cleanup (void *arg)
puts ("second call to cleanup");
exit (1);
}
-
- printf ("cleanup call #%d\n", ncall);
}
@@ -52,17 +51,15 @@ tf (void *arg)
int e = pthread_barrier_wait (&bar);
if (e != 0 && e != PTHREAD_BARRIER_SERIAL_THREAD)
{
- puts ("tf: 1st barrier_wait failed");
+ puts ("error: tf: 1st barrier_wait failed");
exit (1);
}
- /* This call should block and be cancelable. */
+ /* This call should be cancelable. */
sem_wait (&sem);
pthread_cleanup_pop (0);
- puts ("sem_wait returned");
-
return NULL;
}
@@ -74,47 +71,47 @@ do_test (void)
if (pthread_barrier_init (&bar, NULL, 2) != 0)
{
- puts ("barrier_init failed");
+ puts ("error: barrier_init failed");
exit (1);
}
+ /* A value higher than 0 will check for uncontended pthread cancellation,
+ where the sem_wait operation will return immediatelly. */
if (sem_init (&sem, 0, 1) != 0)
{
- puts ("sem_init failed");
+ puts ("error: sem_init failed");
exit (1);
}
if (pthread_create (&th, NULL, tf, NULL) != 0)
{
- puts ("create failed");
+ puts ("error: create failed");
exit (1);
}
- /* Check whether cancellation is honored even before sem_wait does
- anything. */
if (pthread_cancel (th) != 0)
{
- puts ("1st cancel failed");
+ puts ("error: pthread_cancel failed");
exit (1);
}
int e = pthread_barrier_wait (&bar);
if (e != 0 && e != PTHREAD_BARRIER_SERIAL_THREAD)
{
- puts ("1st barrier_wait failed");
+ puts ("error: 1st barrier_wait failed");
exit (1);
}
void *r;
if (pthread_join (th, &r) != 0)
{
- puts ("join failed");
+ puts ("error: pthread_join failed");
exit (1);
}
if (r != PTHREAD_CANCELED)
{
- puts ("thread not canceled");
+ puts ("error: thread not canceled");
exit (1);
}
diff --git a/nptl/tst-cancel13.c b/nptl/tst-cancel13.c
index c84780d..ee39b96 100644
--- a/nptl/tst-cancel13.c
+++ b/nptl/tst-cancel13.c
@@ -1,4 +1,5 @@
-/* Copyright (C) 2003-2016 Free Software Foundation, Inc.
+/* Test sem_wait cancellation for contended case.
+ Copyright (C) 2003-2016 Free Software Foundation, Inc.
This file is part of the GNU C Library.
Contributed by Ulrich Drepper <drepper@redhat.com>, 2003.
@@ -39,8 +40,6 @@ cleanup (void *arg)
puts ("second call to cleanup");
exit (1);
}
-
- printf ("cleanup call #%d\n", ncall);
}
@@ -52,7 +51,7 @@ tf (void *arg)
int e = pthread_barrier_wait (&bar);
if (e != 0 && e != PTHREAD_BARRIER_SERIAL_THREAD)
{
- puts ("tf: 1st barrier_wait failed");
+ puts ("error: tf: 1st barrier_wait failed");
exit (1);
}
@@ -61,8 +60,6 @@ tf (void *arg)
pthread_cleanup_pop (0);
- puts ("sem_wait returned");
-
return NULL;
}
@@ -74,26 +71,28 @@ do_test (void)
if (pthread_barrier_init (&bar, NULL, 2) != 0)
{
- puts ("barrier_init failed");
+ puts ("error: barrier_init failed");
exit (1);
}
+ /* A value equal to 0 will check for contended pthread cancellation,
+ where the sem_wait operation will block. */
if (sem_init (&sem, 0, 0) != 0)
{
- puts ("sem_init failed");
+ puts ("error: sem_init failed");
exit (1);
}
if (pthread_create (&th, NULL, tf, NULL) != 0)
{
- puts ("create failed");
+ puts ("error: create failed");
exit (1);
}
int e = pthread_barrier_wait (&bar);
if (e != 0 && e != PTHREAD_BARRIER_SERIAL_THREAD)
{
- puts ("1st barrier_wait failed");
+ puts ("error: 1st barrier_wait failed");
exit (1);
}
@@ -103,14 +102,14 @@ do_test (void)
/* Check whether cancellation is honored when waiting in sem_wait. */
if (pthread_cancel (th) != 0)
{
- puts ("1st cancel failed");
+ puts ("error: 1st cancel failed");
exit (1);
}
void *r;
if (pthread_join (th, &r) != 0)
{
- puts ("join failed");
+ puts ("error: join failed");
exit (1);
}
diff --git a/nptl/tst-cancel14.c b/nptl/tst-cancel14.c
index 3810d2b..b6fcbb7 100644
--- a/nptl/tst-cancel14.c
+++ b/nptl/tst-cancel14.c
@@ -1,4 +1,5 @@
-/* Copyright (C) 2003-2016 Free Software Foundation, Inc.
+/* Test sem_timedwait cancellation for uncontended case.
+ Copyright (C) 2003-2016 Free Software Foundation, Inc.
This file is part of the GNU C Library.
Contributed by Ulrich Drepper <drepper@redhat.com>, 2003.
@@ -40,8 +41,6 @@ cleanup (void *arg)
puts ("second call to cleanup");
exit (1);
}
-
- printf ("cleanup call #%d\n", ncall);
}
@@ -53,7 +52,7 @@ tf (void *arg)
int e = pthread_barrier_wait (&bar);
if (e != 0 && e != PTHREAD_BARRIER_SERIAL_THREAD)
{
- puts ("tf: 1st barrier_wait failed");
+ puts ("error: tf: 1st barrier_wait failed");
exit (1);
}
@@ -71,8 +70,6 @@ tf (void *arg)
pthread_cleanup_pop (0);
- puts ("sem_timedwait returned");
-
return NULL;
}
@@ -84,19 +81,19 @@ do_test (void)
if (pthread_barrier_init (&bar, NULL, 2) != 0)
{
- puts ("barrier_init failed");
+ puts ("error: barrier_init failed");
exit (1);
}
if (sem_init (&sem, 0, 1) != 0)
{
- puts ("sem_init failed");
+ puts ("error: sem_init failed");
exit (1);
}
if (pthread_create (&th, NULL, tf, NULL) != 0)
{
- puts ("create failed");
+ puts ("error: create failed");
exit (1);
}
@@ -104,7 +101,7 @@ do_test (void)
anything. */
if (pthread_cancel (th) != 0)
{
- puts ("1st cancel failed");
+ puts ("error: 1st cancel failed");
exit (1);
}
diff --git a/nptl/tst-cancel15.c b/nptl/tst-cancel15.c
index f413839..c8db3e4 100644
--- a/nptl/tst-cancel15.c
+++ b/nptl/tst-cancel15.c
@@ -1,4 +1,5 @@
-/* Copyright (C) 2003-2016 Free Software Foundation, Inc.
+/* Test sem_timedwait cancellation for contended case.
+ Copyright (C) 2003-2016 Free Software Foundation, Inc.
This file is part of the GNU C Library.
Contributed by Ulrich Drepper <drepper@redhat.com>, 2003.
@@ -40,8 +41,6 @@ cleanup (void *arg)
puts ("second call to cleanup");
exit (1);
}
-
- printf ("cleanup call #%d\n", ncall);
}
@@ -55,7 +54,7 @@ tf (void *arg)
e = pthread_barrier_wait (&bar);
if (e != 0 && e != PTHREAD_BARRIER_SERIAL_THREAD)
{
- puts ("tf: 1st barrier_wait failed");
+ puts ("error: tf: 1st barrier_wait failed");
exit (1);
}
@@ -74,8 +73,6 @@ tf (void *arg)
pthread_cleanup_pop (0);
- printf ("sem_timedwait returned, e = %d, errno = %d\n", e, errno);
-
return NULL;
}
@@ -87,26 +84,26 @@ do_test (void)
if (pthread_barrier_init (&bar, NULL, 2) != 0)
{
- puts ("barrier_init failed");
+ puts ("error: barrier_init failed");
exit (1);
}
if (sem_init (&sem, 0, 0) != 0)
{
- puts ("sem_init failed");
+ puts ("error: sem_init failed");
exit (1);
}
if (pthread_create (&th, NULL, tf, NULL) != 0)
{
- puts ("create failed");
+ puts ("error: create failed");
exit (1);
}
int e = pthread_barrier_wait (&bar);
if (e != 0 && e != PTHREAD_BARRIER_SERIAL_THREAD)
{
- puts ("1st barrier_wait failed");
+ puts ("error: 1st barrier_wait failed");
exit (1);
}
@@ -116,20 +113,20 @@ do_test (void)
/* Check whether cancellation is honored when waiting in sem_timedwait. */
if (pthread_cancel (th) != 0)
{
- puts ("1st cancel failed");
+ puts ("error: 1st cancel failed");
exit (1);
}
void *r;
if (pthread_join (th, &r) != 0)
{
- puts ("join failed");
+ puts ("error: join failed");
exit (1);
}
if (r != PTHREAD_CANCELED)
{
- puts ("thread not canceled");
+ puts ("error: thread not canceled");
exit (1);
}