write a debug message to the log when we're stuck in the sicko state

of trying to take over scoreboard slots that aren't going to be released
(we could also be stalled while taking over slots if a thread in child
gracefully terminating is serving a long-running request)

update a comment describing the sicko state to remove any information
I'm not absolutely sure of

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@94059 13f79535-47bb-0310-9956-ffa450edef68

diff --git a/server/mpm/worker/worker.c b/server/mpm/worker/worker.c
index f6594e505651280a388fcfee427f10156dabcf0a..e3b5cf03fe769bff3cc131e67d24f435826c7f4a 100644 (file)
--- a/server/mpm/worker/worker.c
+++ b/server/mpm/worker/worker.c
@@ -848,14 +848,10 @@ static int check_signal(int signum)
     return 0;
 }
 
-/* XXX unfortunate issue:
- *     with apachectl restart (not graceful), previous generation dies
- *     abruptly with no chance to clean up scoreboard entries; when new
- *     generation is started, processes can loop forever in start_threads()
- *     waiting for scoreboard entries for threads of prior generation to
- *     get cleaned up...  but it will never happen and the new generation
- *     child looping here, waiting for scoreboard to get cleaned up, is
- *     wasted
+/* XXX under some circumstances not understood, children can get stuck
+ *     in start_threads forever trying to take over slots which will
+ *     never be cleaned up; for now there is an APLOG_DEBUG message issued
+ *     every so often when this condition occurs
  */
 static void * APR_THREAD_FUNC start_threads(apr_thread_t *thd, void *dummy)
 {
@@ -868,6 +864,8 @@ static void * APR_THREAD_FUNC start_threads(apr_thread_t *thd, void *dummy)
     apr_status_t rv;
     int i = 0;
     int threads_created = 0;
+    int loops;
+    int prev_threads_created;
 
     /* We must create the fd queues before we start up the listener
      * and worker threads. */
@@ -898,6 +896,7 @@ static void * APR_THREAD_FUNC start_threads(apr_thread_t *thd, void *dummy)
         clean_child_exit(APEXIT_CHILDFATAL);
     }
     apr_os_thread_get(&listener_os_thread, ts->listener);
+    loops = prev_threads_created = 0;
     while (1) {
         /* ap_threads_per_child does not include the listener thread */
         for (i = 0; i < ap_threads_per_child; i++) {
@@ -941,6 +940,16 @@ static void * APR_THREAD_FUNC start_threads(apr_thread_t *thd, void *dummy)
         }
         /* wait for previous generation to clean up an entry */
         apr_sleep(1 * APR_USEC_PER_SEC);
+        ++loops;
+        if (loops % 120 == 0) { /* every couple of minutes */
+            if (prev_threads_created == threads_created) {
+                ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, ap_server_conf,
+                             "child %" APR_PID_T_FMT " isn't taking over "
+                             "slots very quickly (%d of %d)",
+                             ap_my_pid, threads_created, ap_threads_per_child);
+            }
+            prev_threads_created = threads_created;
+        }
     }
     
     /* What state should this child_main process be listed as in the