On graceless shutdown or restart, send AP_SIG_GRACEFUL to all worker

threads so that any that are polling on Keep-Alive connections will
wake up and exit promptly.  Otherwise, on Linux, they wait until
poll()'s timeout interval completes, which is often too long for
the parent process; the parent issues SIGKILL before the child's main
thread manages to re-join all the worker threads.  PR 38737.

On Solaris, by contrast, the close_worker_sockets() function
successfully alerts all worker threads that they should exit quickly.
On Linux, this side-effect of one thread closing another's socket
doesn't occur; see:

http://bugme.osdl.org/show_bug.cgi?id=546

Also, expand on the placeholder in CHANGES regarding previous
cleanups to scoreboard.c and scoreboard.h in r404848 and r404849.

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@409715 13f79535-47bb-0310-9956-ffa450edef68

diff --git a/CHANGES b/CHANGES
index 942c058b36518899dd70c980d8fce0d74b77a674..8086806bce4685dcac373fb554cec9047a4f39dd 100644 (file)
--- a/CHANGES
+++ b/CHANGES
@@ -2,6 +2,10 @@
 Changes with Apache 2.3.0
   [Remove entries to the current 2.0 and 2.2 section below, when backported]
 
+  *) Worker MPM: On graceless shutdown or restart, send signals to
+     each worker thread to wake them up if they're polling on a
+     Keep-Alive connection.  PR 38737.  [Chris Darroch]
+
   *) Worker and event MPMs: Remove improper scoreboard updates which were
      performed in the event of a fork() failure.  [Chris Darroch]
 
@@ -11,7 +15,13 @@ Changes with Apache 2.3.0
   *) Add support for fcgi:// proxies to mod_rewrite.
      [Markus Schiegl <ms schiegl.com>]
 
-  *) Tidy up scoreboard [Chris Darroch <chrisd pearsoncmg.com> ]
+  *) Remove incorrect comments from scoreboard.h regarding conditional
+     loading of worker_score structure with mod_status, and remove unused
+     definitions relating to old life_status field.
+     [Chris Darroch <chrisd pearsoncmg.com>]
+
+  *) Remove allocation of memory for unused array of lb_score pointers
+     in ap_init_scoreboard().  [Chris Darroch <chrisd pearsoncmg.com>]
 
   *) core, mod_http: add optional 'scheme://' prefix to ServerName directive. 
      For 'https', mod_http returns "https" for the ap_hook_http_scheme and

diff --git a/server/mpm/worker/worker.c b/server/mpm/worker/worker.c
index a4ea5c7adf80f64ba342f85f323a11f02329eea6..7f504fc553625a138848fee7e910e464a34a628b 100644 (file)
--- a/server/mpm/worker/worker.c
+++ b/server/mpm/worker/worker.c
@@ -213,6 +213,19 @@ static apr_proc_mutex_t *accept_mutex;
  */
 #define LISTENER_SIGNAL     SIGHUP
 
+/* The WORKER_SIGNAL signal will be sent from the main thread to the
+ * worker threads during an ungraceful restart or shutdown.
+ * This ensures that on systems (i.e., Linux) where closing the worker
+ * socket doesn't awake the worker thread when it is polling on the socket
+ * (especially in apr_wait_for_io_or_timeout() when handling
+ * Keep-Alive connections), close_worker_sockets() and join_workers()
+ * still function in timely manner and allow ungraceful shutdowns to
+ * proceed to completion.  Otherwise join_workers() doesn't return
+ * before the main process decides the child process is non-responsive
+ * and sends a SIGKILL.
+ */
+#define WORKER_SIGNAL       AP_SIG_GRACEFUL
+
 /* An array of socket descriptors in use by each thread used to
  * perform a non-graceful (forced) shutdown of the server. */
 static apr_socket_t **worker_sockets;
@@ -822,6 +835,11 @@ static void * APR_THREAD_FUNC worker_thread(apr_thread_t *thd, void * dummy)
     ap_scoreboard_image->servers[process_slot][thread_slot].generation = ap_my_generation;
     ap_update_child_status_from_indexes(process_slot, thread_slot, SERVER_STARTING, NULL);
 
+#ifdef HAVE_PTHREAD_KILL
+    unblock_signal(WORKER_SIGNAL);
+    apr_signal(WORKER_SIGNAL, dummy_signal_handler);
+#endif
+
     while (!workers_may_exit) {
         if (!is_idle) {
             rv = ap_queue_info_set_idle(worker_queue_info, last_ptrans);
@@ -1077,6 +1095,13 @@ static void join_workers(apr_thread_t *listener, apr_thread_t **threads)
 
     for (i = 0; i < ap_threads_per_child; i++) {
         if (threads[i]) { /* if we ever created this thread */
+#ifdef HAVE_PTHREAD_KILL
+            apr_os_thread_t *worker_os_thread;
+
+            apr_os_thread_get(&worker_os_thread, threads[i]);
+            pthread_kill(*worker_os_thread, WORKER_SIGNAL);
+#endif
+
             rv = apr_thread_join(&thread_rv, threads[i]);
             if (rv != APR_SUCCESS) {
                 ap_log_error(APLOG_MARK, APLOG_CRIT, rv, ap_server_conf,