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 (file)
index 0000000..f7126bd
--- /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 3f9a063e11758c8e6035ef61e71abc2e7e0ac1b4..cf63634076354ba61f9e0b5f2effafdfdff86135 100644 (file)
--- 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)