From: "Tulio Magno Quites Machado Filho" <tuliom@linux.vnet.ibm.com>
To: libc-alpha@sourceware.org
Subject: [PATCH] Document a behavior of an elided pthread_rwlock_unlock
Date: Fri, 21 Oct 2016 21:06:00 -0000 [thread overview]
Message-ID: <1477083990-9983-1-git-send-email-tuliom@linux.vnet.ibm.com> (raw)
Explain that pthread_rwlock_unlock may crash if called on a lock not
held by the current thread.
2016-10-21 Tulio Magno Quites Machado Filho <tuliom@linux.vnet.ibm.com>
* nptl/pthread_rwlock_unlock.c: Add a comment explaining its
behavior when eliding a lock not held by the current thread.
* sysdeps/powerpc/nptl/elide.h: Likewise.
---
nptl/pthread_rwlock_unlock.c | 4 ++++
sysdeps/powerpc/nptl/elide.h | 2 ++
2 files changed, 6 insertions(+)
diff --git a/nptl/pthread_rwlock_unlock.c b/nptl/pthread_rwlock_unlock.c
index a6cadd4..112f748 100644
--- a/nptl/pthread_rwlock_unlock.c
+++ b/nptl/pthread_rwlock_unlock.c
@@ -35,6 +35,10 @@ __pthread_rwlock_unlock (pthread_rwlock_t *rwlock)
LIBC_PROBE (rwlock_unlock, 1, rwlock);
+ /* Trying to elide an unlocked lock may crash the process. This
+ is expected and is compatible with POSIX.1-2008: "results are
+ undefined if the read-write lock rwlock is not held by the
+ calling thread". */
if (ELIDE_UNLOCK (rwlock->__data.__writer == 0
&& rwlock->__data.__nr_readers == 0))
return 0;
diff --git a/sysdeps/powerpc/nptl/elide.h b/sysdeps/powerpc/nptl/elide.h
index 77bd82e..c573981 100644
--- a/sysdeps/powerpc/nptl/elide.h
+++ b/sysdeps/powerpc/nptl/elide.h
@@ -102,6 +102,8 @@ __elide_unlock (int is_lock_free)
{
if (is_lock_free)
{
+ /* Intentionally crashes when trying to unlock a lock not held by this
+ thread. */
__libc_tend (0);
return true;
}
--
2.1.0
next reply other threads:[~2016-10-21 21:06 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-10-21 21:06 Tulio Magno Quites Machado Filho [this message]
2016-10-24 17:08 ` Torvald Riegel
2016-10-28 20:28 ` Tulio Magno Quites Machado Filho
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