Make global torrent counter atomic and fix the setter and getter

1 files changed, 6 insertions, 3 deletions

diff --git a/ot_mutex.c b/ot_mutex.c
index c44efed..5392264 100644
--- a/ot_mutex.c
+++ b/ot_mutex.c
@@ -26,7 +26,9 @@
 /* Our global all torrents list */
 static ot_vector       all_torrents[OT_BUCKET_COUNT];
 static pthread_mutex_t bucket_mutex[OT_BUCKET_COUNT];
-static size_t          g_torrent_count;
+/* Every bucket's unlock adjusts this, and a bucket lock only keeps other
+   threads out of that one bucket, so the counter needs its own protection */
+static _Atomic size_t  g_torrent_count;
 
 /* Self pipe from opentracker.c */
 extern int             g_self_pipe[2];
@@ -48,14 +50,15 @@ ot_vector *mutex_bucket_lock_by_hash(ot_hash const hash) { return mutex_bucket_l
 
 void mutex_bucket_unlock(int bucket, int delta_torrentcount) {
   pthread_mutex_unlock(bucket_mutex + bucket);
-  g_torrent_count += delta_torrentcount;
+  if (delta_torrentcount)
+    atomic_fetch_add_explicit(&g_torrent_count, (size_t)delta_torrentcount, memory_order_relaxed);
 }
 
 void mutex_bucket_unlock_by_hash(ot_hash const hash, int delta_torrentcount) {
   mutex_bucket_unlock(bucket_from_hash(hash), delta_torrentcount);
 }
 
-size_t mutex_get_torrent_count(void) { return g_torrent_count; }
+size_t mutex_get_torrent_count(void) { return atomic_load_explicit(&g_torrent_count, memory_order_relaxed); }
 
 /* TaskQueue Magic */