From: cypherpunks <cypherpunks@torproject.org>
Date: Thu, 23 Jul 2015 09:28:31 +0000 (+0200)
Subject: Switch order of unblocking threads and releasing the mutex.
X-Git-Tag: tor-0.2.7.3-rc~137
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=b3ea3c8e2f3f49f2633c5283a886de650e3cec78;p=thirdparty%2Ftor.git

Switch order of unblocking threads and releasing the mutex.

According to POSIX, the mutex must be locked by the thread calling the signal
functions to ensure predictable scheduling behavior.

Found the issue using Helgrind which gave the warning `dubious: associated lock
is not held by any thread`.
---

diff --git a/changes/bug16644 b/changes/bug16644
new file mode 100644
index 0000000000..f7126bdc9d
--- /dev/null
+++ b/changes/bug16644
@@ -0,0 +1,3 @@
+  o Minor bugfixes (relay):
+    - Unblock threads before releasing the mutex to ensure predictable
+      scheduling behavior. Fixes bug 16644; bugfix on 0.2.6.3-alpha.
diff --git a/src/common/workqueue.c b/src/common/workqueue.c
index 3f9a063e11..cf63634076 100644
--- a/src/common/workqueue.c
+++ b/src/common/workqueue.c
@@ -293,10 +293,10 @@ threadpool_queue_work(threadpool_t *pool,
 
   TOR_TAILQ_INSERT_TAIL(&pool->work, ent, next_work);
 
-  tor_mutex_release(&pool->lock);
-
   tor_cond_signal_one(&pool->condition);
 
+  tor_mutex_release(&pool->lock);
+
   return ent;
 }
 
@@ -345,10 +345,10 @@ threadpool_queue_update(threadpool_t *pool,
   pool->update_fn = fn;
   ++pool->generation;
 
-  tor_mutex_release(&pool->lock);
-
   tor_cond_signal_all(&pool->condition);
 
+  tor_mutex_release(&pool->lock);
+
   if (old_args) {
     for (i = 0; i < n_threads; ++i) {
       if (old_args[i] && old_args_free_fn)