mpm_event: use apr_atomic_read32() to read queues' ->total instead of volatile access.

* server/mpm/event/event.c (listener_thread): Use apr_atomic_read32() instead
  open coded *(volatile apr_uint32_t*)q->total.

No functional change.

Follow up to r1891716.
Github: #208


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1891718 13f79535-47bb-0310-9956-ffa450edef68
diff --git a/server/mpm/event/event.c b/server/mpm/event/event.c
index b43b05e..1f3d751 100644
--- a/server/mpm/event/event.c
+++ b/server/mpm/event/event.c
@@ -1895,8 +1895,8 @@
                              "keep-alive: %d lingering: %d suspended: %u)",
                              apr_atomic_read32(&connection_count),
                              apr_atomic_read32(&clogged_count),
-                             *(volatile apr_uint32_t*)write_completion_q->total,
-                             *(volatile apr_uint32_t*)keepalive_q->total,
+                             apr_atomic_read32(write_completion_q->total),
+                             apr_atomic_read32(keepalive_q->total),
                              apr_atomic_read32(&lingering_count),
                              apr_atomic_read32(&suspended_count));
                 if (dying) {
@@ -2260,14 +2260,14 @@
                          queues_next_expiry > now ? queues_next_expiry - now
                                                   : -1);
 
-            ps->keep_alive = *(volatile apr_uint32_t*)keepalive_q->total;
-            ps->write_completion = *(volatile apr_uint32_t*)write_completion_q->total;
+            ps->keep_alive = apr_atomic_read32(keepalive_q->total);
+            ps->write_completion = apr_atomic_read32(write_completion_q->total);
             ps->connections = apr_atomic_read32(&connection_count);
             ps->suspended = apr_atomic_read32(&suspended_count);
             ps->lingering_close = apr_atomic_read32(&lingering_count);
         }
         else if ((workers_were_busy || dying)
-                 && *(volatile apr_uint32_t*)keepalive_q->total) {
+                 && apr_atomic_read32(keepalive_q->total)) {
             apr_thread_mutex_lock(timeout_mutex);
             process_keepalive_queue(0); /* kill'em all \m/ */
             apr_thread_mutex_unlock(timeout_mutex);