From: Rich Felker <dalias@aerifal.cx>
Date: Mon, 3 Oct 2011 04:09:08 +0000 (-0400)
Subject: use count=0 instead of 1 for recursive mutex with only one lock reference
X-Git-Url: http://nsz.repo.hu/git/?p=musl;a=commitdiff_plain;h=7fe58d3511387ab6c57909f6e4baef58acd6bd56

use count=0 instead of 1 for recursive mutex with only one lock reference

this simplifies the code paths slightly, but perhaps what's nicer is
that it makes recursive mutexes fully reentrant, i.e. locking and
unlocking from a signal handler works even if the interrupted code was
in the middle of locking or unlocking.
---

diff --git a/src/thread/pthread_mutex_trylock.c b/src/thread/pthread_mutex_trylock.c
index 4a424bc9..fb277970 100644
--- a/src/thread/pthread_mutex_trylock.c
+++ b/src/thread/pthread_mutex_trylock.c
@@ -30,8 +30,6 @@ int pthread_mutex_trylock(pthread_mutex_t *m)
 	if ((own && !(own & 0x40000000)) || a_cas(&m->_m_lock, old, tid)!=old)
 		return EBUSY;
 
-	m->_m_count = 1;
-
 	if (m->_m_type < 4) return 0;
 
 	if (m->_m_type >= 8) {
diff --git a/src/thread/pthread_mutex_unlock.c b/src/thread/pthread_mutex_unlock.c
index 0f4a5e6c..05baec18 100644
--- a/src/thread/pthread_mutex_unlock.c
+++ b/src/thread/pthread_mutex_unlock.c
@@ -12,8 +12,8 @@ int pthread_mutex_unlock(pthread_mutex_t *m)
 		self = __pthread_self();
 		if ((m->_m_lock&0x1fffffff) != self->tid)
 			return EPERM;
-		if ((m->_m_type&3) == PTHREAD_MUTEX_RECURSIVE && --m->_m_count)
-			return 0;
+		if ((m->_m_type&3) == PTHREAD_MUTEX_RECURSIVE && m->_m_count)
+			return m->_m_count--, 0;
 		if (m->_m_type >= 4) {
 			self->robust_list.pending = &m->_m_next;
 			*(void **)m->_m_prev = m->_m_next;