MonetDB: default - Fix a race condition in dead thread cleanup c...

[Sjoerd Mullender]

Changeset: d21bbc3df6ac for MonetDB
URL: http://dev.monetdb.org/hg/MonetDB?cmd=changeset;node=d21bbc3df6ac
Modified Files:
        gdk/gdk_system.c
Branch: default
Log Message:

Fix a race condition in dead thread cleanup code.


diffs (63 lines):

diff --git a/gdk/gdk_system.c b/gdk/gdk_system.c
--- a/gdk/gdk_system.c
+++ b/gdk/gdk_system.c
@@ -482,16 +482,18 @@ MT_thread_sigmask(sigset_t * new_mask, s
 #endif
 
 static void
-rm_posthread(struct posthread *p)
+rm_posthread(struct posthread *p, int lock)
 {
        struct posthread **pp;
 
-       pthread_mutex_lock(&posthread_lock);
+       if (lock)
+               pthread_mutex_lock(&posthread_lock);
        for (pp = &posthreads; *pp && *pp != p; pp = &(*pp)->next)
                ;
        if (*pp)
                *pp = p->next;
-       pthread_mutex_unlock(&posthread_lock);
+       if (lock)
+               pthread_mutex_unlock(&posthread_lock);
        free(p);
 }
 
@@ -509,22 +511,24 @@ join_threads(void)
 {
        struct posthread *p;
        int waited;
+       pthread_t tid;
 
+       pthread_mutex_lock(&posthread_lock);
        do {
                waited = 0;
-               pthread_mutex_lock(&posthread_lock);
                for (p = posthreads; p; p = p->next) {
                        if (p->exited) {
+                               tid = p->tid;
+                               rm_posthread(p, 0);
                                pthread_mutex_unlock(&posthread_lock);
-                               pthread_join(p->tid, NULL);
-                               rm_posthread(p);
+                               pthread_join(tid, NULL);
                                pthread_mutex_lock(&posthread_lock);
                                waited = 1;
                                break;
                        }
                }
-               pthread_mutex_unlock(&posthread_lock);
        } while (waited);
+       pthread_mutex_unlock(&posthread_lock);
 }
 
 int
@@ -570,7 +574,7 @@ MT_create_thread(MT_Id *t, void (*f) (vo
                *t = (MT_Id) (((size_t) newt) + 1);     /* use pthread-id + 1 */
 #endif
        } else if (p) {
-               rm_posthread(p);
+               rm_posthread(p, 1);
        }
 #ifdef HAVE_PTHREAD_SIGMASK
        MT_thread_sigmask(&orig_mask, NULL);
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