Changeset: 478f2e4ef2c9 for MonetDB
URL: http://dev.monetdb.org/hg/MonetDB?cmd=changeset;node=478f2e4ef2c9
Modified Files:
gdk/gdk_system.c
Branch: Oct2014
Log Message:
Work around issue found by Coverity.
Coverity complained about non-atomic use of the variable p in
join_threads. The pointer was set when the lock was held, then the
lock was released and reacquired. The pointer should then not be used
again, since another thread might have done something to it in the
mean time.
diffs (116 lines):
diff --git a/gdk/gdk_system.c b/gdk/gdk_system.c
--- a/gdk/gdk_system.c
+++ b/gdk/gdk_system.c
@@ -473,6 +473,28 @@ static struct posthread {
} *posthreads = NULL;
static pthread_mutex_t posthread_lock = PTHREAD_MUTEX_INITIALIZER;
+static struct posthread *
+find_posthread_locked(pthread_t tid)
+{
+ struct posthread *p;
+
+ for (p = posthreads; p; p = p->next)
+ if (p->tid == tid)
+ return p;
+ return NULL;
+}
+
+static struct posthread *
+find_posthread(pthread_t tid)
+{
+ struct posthread *p;
+
+ pthread_mutex_lock(&posthread_lock);
+ p = find_posthread_locked(tid);
+ pthread_mutex_unlock(&posthread_lock);
+ return p;
+}
+
static void
MT_thread_sigmask(sigset_t * new_mask, sigset_t * orig_mask)
{
@@ -483,18 +505,22 @@ MT_thread_sigmask(sigset_t * new_mask, s
#endif
static void
-rm_posthread(struct posthread *p, int lock)
+rm_posthread_locked(struct posthread *p)
{
struct posthread **pp;
- if (lock)
- pthread_mutex_lock(&posthread_lock);
for (pp = &posthreads; *pp && *pp != p; pp = &(*pp)->next)
;
if (*pp)
*pp = p->next;
- if (lock)
- pthread_mutex_unlock(&posthread_lock);
+}
+
+static void
+rm_posthread(struct posthread *p)
+{
+ pthread_mutex_lock(&posthread_lock);
+ rm_posthread_locked(p);
+ pthread_mutex_unlock(&posthread_lock);
}
static void
@@ -522,10 +548,14 @@ join_threads(void)
n = p->next;
if (p->exited) {
tid = p->tid;
- rm_posthread(p, 0);
pthread_mutex_unlock(&posthread_lock);
pthread_join(tid, NULL);
pthread_mutex_lock(&posthread_lock);
+ /* find the thread again, mostly to
+ * keep Coverity happy */
+ p = find_posthread_locked(tid);
+ assert(p != NULL);
+ rm_posthread_locked(p);
free(p);
waited = 1;
break;
@@ -578,7 +608,7 @@ MT_create_thread(MT_Id *t, void (*f) (vo
*t = (MT_Id) (((size_t) *newtp) + 1); /* use pthread-id + 1 */
#endif
} else if (p) {
- rm_posthread(p, 1);
+ rm_posthread(p);
free(p);
}
#ifdef HAVE_PTHREAD_SIGMASK
@@ -587,26 +617,16 @@ MT_create_thread(MT_Id *t, void (*f) (vo
return ret;
}
-static struct posthread *
-find_posthread(pthread_t tid)
-{
- struct posthread *p;
-
- pthread_mutex_lock(&posthread_lock);
- for (p = posthreads; p; p = p->next)
- if (p->tid == tid)
- break;
- pthread_mutex_unlock(&posthread_lock);
- return p;
-}
-
void
MT_exiting_thread(void)
{
struct posthread *p;
+ pthread_t tid = pthread_self();
- if ((p = find_posthread(pthread_self())) != NULL)
+ pthread_mutex_lock(&posthread_lock);
+ if ((p = find_posthread_locked(tid)) != NULL)
p->exited = 1;
+ pthread_mutex_unlock(&posthread_lock);
}
void
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