fix deadlock in condition wait whenever there are multiple waiters

[musl] / src / thread / pthread_cond_timedwait.c

diff --git a/src/thread/pthread_cond_timedwait.c b/src/thread/pthread_cond_timedwait.c
index ee874a3..ec5aa6f 100644 (file)
--- a/src/thread/pthread_cond_timedwait.c
+++ b/src/thread/pthread_cond_timedwait.c
@@ -1,12 +1,20 @@
 #include "pthread_impl.h"
 
-static void relock(void *m)
+struct cm {
+       pthread_cond_t *c;
+       pthread_mutex_t *m;
+};
+
+static void cleanup(void *p)
 {
-       pthread_mutex_lock(m);
+       struct cm *cm = p;
+       a_dec(&cm->c->_c_waiters);
+       pthread_mutex_lock(cm->m);
 }
 
 int pthread_cond_timedwait(pthread_cond_t *c, pthread_mutex_t *m, const struct timespec *ts)
 {
+       struct cm cm = { .c=c, .m=m };
        int r, e=0;
 
        if (ts && ts->tv_nsec >= 1000000000UL)
@@ -17,8 +25,10 @@ int pthread_cond_timedwait(pthread_cond_t *c, pthread_mutex_t *m, const struct t
        c->_c_block = 1;
        if ((r=pthread_mutex_unlock(m))) return r;
 
-       do e = __timedwait(&c->_c_block, 1, c->_c_clock, ts, relock, m, 0);
+       a_inc(&c->_c_waiters);
+       do e = __timedwait(&c->_c_block, 1, c->_c_clock, ts, cleanup, &cm, 0);
        while (e == EINTR);
+       a_dec(&c->_c_waiters);
 
        if ((r=pthread_mutex_lock(m))) return r;