In the current code, rdlock_count is not correctly handled for some cases.

The most notable is that it is not bumped in rwlock_rdlock_common() when
the hard path (__thr_rwlock_rdlock()) returns successfully.
This can lead to deadlocks in libthr when rwlocks recursion in read mode
happens.
Fix the interested parts by correctly handling rdlock_count.

PR:		threads/136345
Reported by:	rink
Tested by:	rink
Reviewed by:	jeff
Approved by:	re (kib)
MFC:		2 weeks

2 files changed, 4 insertions, 1 deletions

diff --git a/lib/libthr/thread/thr_rtld.c b/lib/libthr/thread/thr_rtld.c
index 7e26340..4db08bd 100644
--- a/lib/libthr/thread/thr_rtld.c
+++ b/lib/libthr/thread/thr_rtld.c
@@ -114,6 +114,7 @@ _thr_rtld_rlock_acquire(void *lock)
 	THR_CRITICAL_ENTER(curthread);
 	while (_thr_rwlock_rdlock(&l->lock, 0, NULL) != 0)
 		;
+	curthread->rdlock_count++;
 	RESTORE_ERRNO();
 }
 
@@ -148,6 +149,7 @@ _thr_rtld_lock_release(void *lock)
 	
 	state = l->lock.rw_state;
 	if (_thr_rwlock_unlock(&l->lock) == 0) {
+		curthread->rdlock_count--;
 		if ((state & URWLOCK_WRITE_OWNER) == 0) {
 			THR_CRITICAL_LEAVE(curthread);
 		} else {
diff --git a/lib/libthr/thread/thr_rwlock.c b/lib/libthr/thread/thr_rwlock.c
index 641749b..de61e51 100644
--- a/lib/libthr/thread/thr_rwlock.c
+++ b/lib/libthr/thread/thr_rwlock.c
@@ -177,10 +177,11 @@ rwlock_rdlock_common(pthread_rwlock_t *rwlock, const struct timespec *abstime)
 		/* if interrupted, try to lock it in userland again. */
 		if (_thr_rwlock_tryrdlock(&prwlock->lock, flags) == 0) {
 			ret = 0;
-			curthread->rdlock_count++;
 			break;
 		}
 	}
+	if (ret == 0)
+		curthread->rdlock_count++;
 	return (ret);
 }