Keep affinity of threadpool threads the same as the main thread on entry

Keep affinity of threadpool threads the same as the main thread on entry, regardless of later changes to the main thread. This makes sure that we don't pin the threadpool threads to one CPU when the engine_pin() function is in effect.

Fixes #846 (closed)

src/engine.c

@@ -2913,6 +2913,11 @@ void engine_pin(void) {
 
 #ifdef HAVE_SETAFFINITY
   cpu_set_t *entry_affinity = engine_entry_affinity();
+
+  /* Share this affinity with the threadpool, it will use this even when the
+   * main thread is otherwise pinned. */
+  threadpool_set_affinity_mask(entry_affinity);
+
   int pin;
   for (pin = 0; pin < CPU_SETSIZE && !CPU_ISSET(pin, entry_affinity); ++pin)
     ;