diff options
Diffstat (limited to 'linuxthreads/spinlock.c')
| -rw-r--r-- | linuxthreads/spinlock.c | 24 |
1 files changed, 23 insertions, 1 deletions
diff --git a/linuxthreads/spinlock.c b/linuxthreads/spinlock.c index ce6ff9e310..b1a99d9753 100644 --- a/linuxthreads/spinlock.c +++ b/linuxthreads/spinlock.c @@ -40,6 +40,7 @@ void internal_function __pthread_lock(struct _pthread_fastlock * lock, pthread_descr self) { long oldstatus, newstatus; + int spurious_wakeup_count = 0; do { oldstatus = lock->__status; @@ -56,7 +57,28 @@ void internal_function __pthread_lock(struct _pthread_fastlock * lock, } } while(! compare_and_swap(&lock->__status, oldstatus, newstatus, &lock->__spinlock)); - if (oldstatus != 0) suspend(self); + + /* Suspend with guard against spurious wakeup. + This can happen in pthread_cond_timedwait_relative, when the thread + wakes up due to timeout and is still on the condvar queue, and then + locks the queue to remove itself. At that point it may still be on the + queue, and may be resumed by a condition signal. */ + + if (oldstatus != 0) { + for (;;) { + suspend(self); + if (self->p_nextlock != NULL) { + /* Count resumes that don't belong to us. */ + spurious_wakeup_count++; + continue; + } + break; + } + } + + /* Put back any resumes we caught that don't belong to us. */ + while (spurious_wakeup_count--) + restart(self); } void internal_function __pthread_unlock(struct _pthread_fastlock * lock) |