Queue consensus diffs at LOW priority.

Fixes bug 22883.

changes/bug22883-priority

@@ -0,0 +1,8 @@
+  o Major bugfixes (relay, performance):
+
+    - Perform circuit handshake operations at a higher priority than we use
+      for consensus diff creation and compression. This should prevent
+      circuits from starving when a relay or bridge receive a new consensus,
+      especially on lower-powered machines. Fixes bug 22883; bugfix on
+      0.3.1.1-alpha.
+

src/or/consdiffmgr.c

@@ -1605,7 +1605,8 @@ consensus_diff_queue_diff_work(consensus_cache_entry_t *diff_from,
     goto err;
 
   workqueue_entry_t *work;
-  work = cpuworker_queue_work(consensus_diff_worker_threadfn,
+  work = cpuworker_queue_work(WQ_PRI_LOW,
+                              consensus_diff_worker_threadfn,
                               consensus_diff_worker_replyfn,
                               job);
   if (!work)
@@ -1768,7 +1769,8 @@ consensus_queue_compression_work(const char *consensus,
 
   if (background_compression) {
     workqueue_entry_t *work;
-    work = cpuworker_queue_work(consensus_compress_worker_threadfn,
+    work = cpuworker_queue_work(WQ_PRI_LOW,
+                                consensus_compress_worker_threadfn,
                                 consensus_compress_worker_replyfn,
                                 job);
     if (!work) {

src/or/cpuworker.c

@@ -481,16 +481,18 @@ queue_pending_tasks(void)
 
 /** DOCDOC */
 MOCK_IMPL(workqueue_entry_t *,
-cpuworker_queue_work,(workqueue_reply_t (*fn)(void *, void *),
+cpuworker_queue_work,(workqueue_priority_t priority,
+                      workqueue_reply_t (*fn)(void *, void *),
                       void (*reply_fn)(void *),
                       void *arg))
 {
   tor_assert(threadpool);
 
-  return threadpool_queue_work(threadpool,
-                               fn,
-                               reply_fn,
-                               arg);
+  return threadpool_queue_work_priority(threadpool,
+                                        priority,
+                                        fn,
+                                        reply_fn,
+                                        arg);
 }
 
 /** Try to tell a cpuworker to perform the public key operations necessary to
@@ -545,7 +547,8 @@ assign_onionskin_to_cpuworker(or_circuit_t *circ,
   memwipe(&req, 0, sizeof(req));
 
   ++total_pending_tasks;
-  queue_entry = threadpool_queue_work(threadpool,
+  queue_entry = threadpool_queue_work_priority(threadpool,
+                                      WQ_PRI_HIGH,
                                       cpuworker_onion_handshake_threadfn,
                                       cpuworker_onion_handshake_replyfn,
                                       job);

src/or/cpuworker.h

@@ -16,7 +16,9 @@ void cpu_init(void);
 void cpuworkers_rotate_keyinfo(void);
 struct workqueue_entry_s;
 enum workqueue_reply_t;
+enum workqueue_priority_t;
 MOCK_DECL(struct workqueue_entry_s *, cpuworker_queue_work, (
+                    enum workqueue_priority_t priority,
                     enum workqueue_reply_t (*fn)(void *, void *),
                     void (*reply_fn)(void *),
                     void *arg));

src/test/test_consdiffmgr.c

@@ -98,10 +98,13 @@ typedef struct fake_work_queue_ent_t {
   void *arg;
 } fake_work_queue_ent_t;
 static struct workqueue_entry_s *
-mock_cpuworker_queue_work(enum workqueue_reply_t (*fn)(void *, void *),
+mock_cpuworker_queue_work(workqueue_priority_t prio,
+                          enum workqueue_reply_t (*fn)(void *, void *),
                           void (*reply_fn)(void *),
                           void *arg)
 {
+  (void) prio;
+
   if (! fake_cpuworker_queue)
     fake_cpuworker_queue = smartlist_new();