tor

commit 250c88014d81fcd4406359d44c9f3f3432844a2f
parent 0ae0b5aa4136fe6df7863c8a5b7d239d519b7393
Author: Nick Mathewson <nickm@torproject.org>
Date:   Wed, 12 Jul 2017 12:23:33 -0400

Always start with one additional worker thread

Now that half the threads are permissive and half are strict, we
need to make sure we have at least two threads, so that we'll
have at least one of each kind.

Diffstat:
A
changes/more-threads
 | 
3
+++
M
src/or/cpuworker.c
 | 
9
++++++++-

2 files changed, 11 insertions(+), 1 deletion(-)
diff --git a/changes/more-threads b/changes/more-threads
@@ -0,0 +1,3 @@
+  o Minor features (relay, performance):
+    - Always start relays with at least two worker threads, to prevent
+      priority inversion on slow tasks.  Part of the fix for bug 22883.
diff --git a/src/or/cpuworker.c b/src/or/cpuworker.c
@@ -89,7 +89,14 @@ cpu_init(void)
     event_add(reply_event, NULL);
   }
   if (!threadpool) {
-    threadpool = threadpool_new(get_num_cpus(get_options()),
+    /*
+      In our threadpool implementation, half the threads are permissive and
+      half are strict (when it comes to running lower-priority tasks). So we
+      always make sure we have at least two threads, so that there will be at
+      least one thread of each kind.
+    */
+    const int n_threads = get_num_cpus(get_options()) + 1;
+    threadpool = threadpool_new(n_threads,
                                 replyqueue,
                                 worker_state_new,
                                 worker_state_free,