From 3e926ca209e9ed7946d8287e579bdaff05f3c2b3 Mon Sep 17 00:00:00 2001
From: Dirk Engling <erdgeist@erdgeist.org>
Date: Thu, 5 Nov 2026 19:00:31 +0100
Subject: Use poll instead of a condition variable to time the sleepers

---
 src/ot_clean.c | 45 ++++++++++++++++++++++-----------------------
 1 file changed, 22 insertions(+), 23 deletions(-)

(limited to 'src')

diff --git a/src/ot_clean.c b/src/ot_clean.c
index 2ebfd42..dfac011 100644
--- a/src/ot_clean.c
+++ b/src/ot_clean.c
@@ -2,8 +2,9 @@
    It is considered beerware. Prost. Skol. Cheers or whatever. */
 
 /* System */
-#include <errno.h>
+#include <poll.h>
 #include <pthread.h>
+#include <stdio.h>
 #include <string.h>
 #include <unistd.h>
 
@@ -102,27 +103,18 @@ int clean_single_torrent(ot_torrent *torrent) {
   return clean_single_peer_list(torrent->peer_list6, OT_PEER_SIZE6) * clean_single_peer_list(torrent->peer_list4, OT_PEER_SIZE4);
 }
 
-static pthread_mutex_t g_clean_mutex  = PTHREAD_MUTEX_INITIALIZER;
-static pthread_cond_t  g_clean_wakeup = PTHREAD_COND_INITIALIZER;
+/* Written to once, by clean_deinit, and never read: the byte stays in and
+   every sleep after it returns at once */
+static int g_clean_pipe[2] = {-1, -1};
 
 static void clean_sleep(void) {
-  struct timespec deadline;
-
-  clock_gettime(CLOCK_REALTIME, &deadline);
-  deadline.tv_sec  += OT_CLEAN_SLEEP / 1000000;
-  deadline.tv_nsec += (OT_CLEAN_SLEEP % 1000000) * 1000;
-  if (deadline.tv_nsec >= 1000000000) {
-    ++deadline.tv_sec;
-    deadline.tv_nsec -= 1000000000;
-  }
+  struct pollfd pfd;
 
-  /* Both sides hold the mutex, so the flag cannot be cleared and signalled
-     in the window between testing it and waiting on it */
-  pthread_mutex_lock(&g_clean_mutex);
-  while (g_opentracker_running)
-    if (pthread_cond_timedwait(&g_clean_wakeup, &g_clean_mutex, &deadline) == ETIMEDOUT)
-      break;
-  pthread_mutex_unlock(&g_clean_mutex);
+  pfd.fd      = g_clean_pipe[0];
+  pfd.events  = POLLIN;
+  pfd.revents = 0;
+
+  poll(&pfd, 1, OT_CLEAN_SLEEP / 1000);
 }
 
 /* Clean up all peers in one bucket, remove timedout pools and torrents */
@@ -166,11 +158,18 @@ static void *clean_worker(void *args) {
 }
 
 static pthread_t thread_id;
-void clean_init(void) { pthread_create(&thread_id, NULL, clean_worker, NULL); }
+void clean_init(void) {
+  if (pipe(g_clean_pipe) == -1)
+    fprintf(stderr, "Warning: the cleaner has no pipe to be woken through and will take up to one sleep interval to stop.\n");
+  pthread_create(&thread_id, NULL, clean_worker, NULL);
+}
 
 void clean_deinit(void) {
-  pthread_mutex_lock(&g_clean_mutex);
-  pthread_cond_signal(&g_clean_wakeup);
-  pthread_mutex_unlock(&g_clean_mutex);
+  const char byte = 0;
+
+  (void)!write(g_clean_pipe[1], &byte, 1);
   pthread_join(thread_id, NULL);
+
+  close(g_clean_pipe[0]);
+  close(g_clean_pipe[1]);
 }
-- 
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