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`.

1 files changed, 4 insertions, 4 deletions

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)