From 361f679c652647cdea4d5a66999a4b96c1653576 Mon Sep 17 00:00:00 2001 From: Leonid Lisovskiy Date: Sun, 29 May 2016 10:06:55 +0300 Subject: linuxthreads.old: Fix segfault when pthread_mutex_unlock() called against unlocked NORMAL mutex. Althought, it is undefined behavior, there is no reason for segfault. Program received signal SIGSEGV, Segmentation fault. __pthread_unlock (lock=lock@entry=0x804b03c ) at libpthread/linuxthreads.old/spinlock.c:231 231 (&lock->__status, oldstatus, (long)(thr->p_nextlock) & ~1L)) It occurs only on platforms which has HAS_COMPARE_AND_SWAP defined. Restore glibc commit fbaf6e72d6 "spinlock.c (__pthread_unlock): Don't crash if called for an untaken mutex." behavior, broken later by commit 4ad1d0cfbf. Signed-off-by: Leonid Lisovskiy --- libpthread/linuxthreads/spinlock.c | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-) (limited to 'libpthread') diff --git a/libpthread/linuxthreads/spinlock.c b/libpthread/linuxthreads/spinlock.c index 80aeda529..ce970029e 100644 --- a/libpthread/linuxthreads/spinlock.c +++ b/libpthread/linuxthreads/spinlock.c @@ -188,10 +188,16 @@ int __pthread_unlock(struct _pthread_fastlock * lock) WRITE_MEMORY_BARRIER(); again: - while ((oldstatus = lock->__status) == 1) { - if (__compare_and_swap_with_release_semantics(&lock->__status, + oldstatus = lock->__status; + if (oldstatus == 0 || oldstatus == 1) { + /* No threads are waiting for this lock. Please note that we also + enter this case if the lock is not taken at all. If this wouldn't + be done here we would crash further down. */ + if (! __compare_and_swap_with_release_semantics(&lock->__status, oldstatus, 0)) - return 0; + goto again; + + return 0; } /* Find thread in waiting queue with maximal priority */ -- cgit v1.2.3