Event loop: call after sleep() only from top level.

In general we do not want before/after sleep() callbacks to be called
when we re-enter the event loop, since those calls are only designed in
order to perform operations every main iteration of the event loop, and
re-entering is often just a way to incrementally serve clietns with
error messages or other auxiliary operations. However, if we call the
callbacks, we are then forced to think at before/after sleep callbacks
as re-entrant, which is much harder without any good need.

However here there was also a clear bug: beforeSleep() was actually
never called when re-entering the event loop. But the new afterSleep()
callback was. This is broken and in this instance re-entering
afterSleep() caused a modules GIL dead lock.

src/ae.c

@@ -344,6 +344,7 @@ static int processTimeEvents(aeEventLoop *eventLoop) {
  * if flags has AE_FILE_EVENTS set, file events are processed.
  * if flags has AE_TIME_EVENTS set, time events are processed.
  * if flags has AE_DONT_WAIT set the function returns ASAP until all
+ * if flags has AE_CALL_AFTER_SLEEP set, the aftersleep callback is called.
  * the events that's possible to process without to wait are processed.
  *
  * The function returns the number of events processed. */
@@ -403,7 +404,7 @@ int aeProcessEvents(aeEventLoop *eventLoop, int flags)
         numevents = aeApiPoll(eventLoop, tvp);
 
         /* After sleep callback. */
-        if (eventLoop->aftersleep != NULL)
+        if (eventLoop->aftersleep != NULL && flags & AE_CALL_AFTER_SLEEP)
             eventLoop->aftersleep(eventLoop);
 
         for (j = 0; j < numevents; j++) {
@@ -460,7 +461,7 @@ void aeMain(aeEventLoop *eventLoop) {
     while (!eventLoop->stop) {
         if (eventLoop->beforesleep != NULL)
             eventLoop->beforesleep(eventLoop);
-        aeProcessEvents(eventLoop, AE_ALL_EVENTS);
+        aeProcessEvents(eventLoop, AE_ALL_EVENTS|AE_CALL_AFTER_SLEEP);
     }
 }
 

src/ae.h

@@ -46,6 +46,7 @@
 #define AE_TIME_EVENTS 2
 #define AE_ALL_EVENTS (AE_FILE_EVENTS|AE_TIME_EVENTS)
 #define AE_DONT_WAIT 4
+#define AE_CALL_AFTER_SLEEP 8
 
 #define AE_NOMORE -1
 #define AE_DELETED_EVENT_ID -1