Add child_status hook for tracking creation/termination of MPM child

processes.  Add end_generation hook for notification when the last
MPM child of a generation exits.

end_generation is implemented completely by core using the
child_status hook run by the MPM.

simple and mpmt_os2 MPMs don't currently run the child_status
hook, so neither hook is invoked with those MPMs.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1096609 13f79535-47bb-0310-9956-ffa450edef68

5 files changed, 164 insertions, 40 deletions

diff --git a/server/mpm/event/event.c b/server/mpm/event/event.c
index 6efd2f73e2..4efcc903a6 100644
--- a/server/mpm/event/event.c
+++ b/server/mpm/event/event.c
@@ -424,9 +424,47 @@ static int event_query(int query_code, int *result, apr_status_t *rv)
     return OK;
 }
 
-static void event_note_child_killed(int childnum)
+static void event_note_child_killed(int childnum, pid_t pid, ap_generation_t gen)
 {
-    ap_scoreboard_image->parent[childnum].pid = 0;
+    if (childnum != -1) { /* child had a scoreboard slot? */
+        ap_run_child_status(ap_server_conf,
+                            ap_scoreboard_image->parent[childnum].pid,
+                            ap_scoreboard_image->parent[childnum].generation,
+                            childnum, MPM_CHILD_EXITED);
+        ap_scoreboard_image->parent[childnum].pid = 0;
+    }
+    else {
+        ap_run_child_status(ap_server_conf, pid, gen, -1, MPM_CHILD_EXITED);
+    }
+}
+
+static void event_note_child_started(int slot, pid_t pid)
+{
+    ap_scoreboard_image->parent[slot].pid = pid;
+    ap_run_child_status(ap_server_conf,
+                        ap_scoreboard_image->parent[slot].pid,
+                        retained->my_generation, slot, MPM_CHILD_STARTED);
+}
+
+static void event_note_child_lost_slot(int slot, pid_t newpid)
+{
+    ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, ap_server_conf,
+                 "pid %" APR_PID_T_FMT " taking over scoreboard slot from "
+                 "%" APR_PID_T_FMT "%s",
+                 newpid,
+                 ap_scoreboard_image->parent[slot].pid,
+                 ap_scoreboard_image->parent[slot].quiescing ?
+                 " (quiescing)" : "");
+    ap_run_child_status(ap_server_conf,
+                        ap_scoreboard_image->parent[slot].pid,
+                        ap_scoreboard_image->parent[slot].generation,
+                        slot, MPM_CHILD_LOST_SLOT);
+    /* Don't forget about this exiting child process, or we
+     * won't be able to kill it if it doesn't exit by the
+     * time the server is shut down.
+     */
+    ap_register_extra_mpm_process(ap_scoreboard_image->parent[slot].pid,
+                                  ap_scoreboard_image->parent[slot].generation);
 }
 
 static const char *event_get_name(void)
@@ -442,6 +480,11 @@ static void clean_child_exit(int code)
     if (pchild) {
         apr_pool_destroy(pchild);
     }
+
+    if (one_process) {
+        event_note_child_killed(/* slot */ 0, 0, 0);
+    }
+
     exit(code);
 }
 
@@ -1847,7 +1890,7 @@ static int make_child(server_rec * s, int slot)
 
     if (one_process) {
         set_signals();
-        ap_scoreboard_image->parent[slot].pid = getpid();
+        event_note_child_started(slot, getpid());
         child_main(slot);
         /* NOTREACHED */
     }
@@ -1894,19 +1937,11 @@ static int make_child(server_rec * s, int slot)
         /* This new child process is squatting on the scoreboard
          * entry owned by an exiting child process, which cannot
          * exit until all active requests complete.
-         * Don't forget about this exiting child process, or we
-         * won't be able to kill it if it doesn't exit by the
-         * time the server is shut down.
          */
-        ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, ap_server_conf,
-                     "taking over scoreboard slot from %" APR_PID_T_FMT "%s",
-                     ap_scoreboard_image->parent[slot].pid,
-                     ap_scoreboard_image->parent[slot].quiescing ?
-                         " (quiescing)" : "");
-        ap_register_extra_mpm_process(ap_scoreboard_image->parent[slot].pid);
+        event_note_child_lost_slot(slot, pid);
     }
     ap_scoreboard_image->parent[slot].quiescing = 0;
-    ap_scoreboard_image->parent[slot].pid = pid;
+    event_note_child_started(slot, pid);
     return 0;
 }
 
@@ -2104,6 +2139,7 @@ static void perform_idle_server_maintenance(void)
 
 static void server_main_loop(int remaining_children_to_start)
 {
+    ap_generation_t old_gen;
     int child_slot;
     apr_exit_why_e exitwhy;
     int status, processed_status;
@@ -2134,7 +2170,7 @@ static void server_main_loop(int remaining_children_to_start)
                                                         SERVER_DEAD,
                                                         (request_rec *) NULL);
 
-                ap_scoreboard_image->parent[child_slot].pid = 0;
+                event_note_child_killed(child_slot, 0, 0);
                 ap_scoreboard_image->parent[child_slot].quiescing = 0;
                 if (processed_status == APEXIT_CHILDSICK) {
                     /* resource shortage, minimize the fork rate */
@@ -2149,8 +2185,10 @@ static void server_main_loop(int remaining_children_to_start)
                     --remaining_children_to_start;
                 }
             }
-            else if (ap_unregister_extra_mpm_process(pid.pid) == 1) {
-                /* handled */
+            else if (ap_unregister_extra_mpm_process(pid.pid, &old_gen) == 1) {
+
+                event_note_child_killed(-1, /* already out of the scoreboard */
+                                        pid.pid, old_gen);
 #if APR_HAS_OTHER_CHILD
             }
             else if (apr_proc_other_child_alert(&pid, APR_OC_REASON_DEATH,
diff --git a/server/mpm/netware/mpm_netware.c b/server/mpm/netware/mpm_netware.c
index 00b2b5ef67..f30fcbf354 100644
--- a/server/mpm/netware/mpm_netware.c
+++ b/server/mpm/netware/mpm_netware.c
@@ -880,6 +880,11 @@ static int netware_run(apr_pool_t *_pconf, apr_pool_t *plog, server_rec *s)
 
     /* Only set slot 0 since that is all NetWare will ever have. */
     ap_scoreboard_image->parent[0].pid = getpid();
+    ap_run_child_status(ap_server_conf,
+                        ap_scoreboard_image->parent[0].pid,
+                        ap_my_generation,
+                        0,
+                        MPM_CHILD_STARTED);
 
     set_signals();
 
@@ -917,6 +922,11 @@ static int netware_run(apr_pool_t *_pconf, apr_pool_t *plog, server_rec *s)
     }
     mpm_state = AP_MPMQ_STOPPING;
 
+    ap_run_child_status(ap_server_conf,
+                        ap_scoreboard_image->parent[0].pid,
+                        ap_my_generation,
+                        0,
+                        MPM_CHILD_EXITED);
 
     /* Shutdown the listen sockets so that we don't get stuck in a blocking call.
     shutdown_listeners();*/
diff --git a/server/mpm/prefork/prefork.c b/server/mpm/prefork/prefork.c
index 86c8d8c15d..eecd17739c 100644
--- a/server/mpm/prefork/prefork.c
+++ b/server/mpm/prefork/prefork.c
@@ -189,6 +189,25 @@ static void chdir_for_gprof(void)
 #define chdir_for_gprof()
 #endif
 
+static void prefork_note_child_killed(int childnum, pid_t pid,
+                                      ap_generation_t gen)
+{
+    AP_DEBUG_ASSERT(childnum != -1); /* no scoreboard squatting with this MPM */
+    ap_run_child_status(ap_server_conf,
+                        ap_scoreboard_image->parent[childnum].pid,
+                        ap_scoreboard_image->parent[childnum].generation,
+                        childnum, MPM_CHILD_EXITED);
+    ap_scoreboard_image->parent[childnum].pid = 0;
+}
+
+static void prefork_note_child_started(int slot, pid_t pid)
+{
+    ap_scoreboard_image->parent[slot].pid = pid;
+    ap_run_child_status(ap_server_conf,
+                        ap_scoreboard_image->parent[slot].pid,
+                        retained->my_generation, slot, MPM_CHILD_STARTED);
+}
+
 /* a clean exit from a child with proper cleanup */
 static void clean_child_exit(int code) __attribute__ ((noreturn));
 static void clean_child_exit(int code)
@@ -198,6 +217,11 @@ static void clean_child_exit(int code)
     if (pchild) {
         apr_pool_destroy(pchild);
     }
+
+    if (one_process) {
+        prefork_note_child_killed(/* slot */ 0, 0, 0);
+    }
+
     ap_mpm_pod_close(pod);
     chdir_for_gprof();
     exit(code);
@@ -306,11 +330,6 @@ static int prefork_query(int query_code, int *result, apr_status_t *rv)
     return OK;
 }
 
-static void prefork_note_child_killed(int childnum)
-{
-    ap_scoreboard_image->parent[childnum].pid = 0;
-}
-
 static const char *prefork_get_name(void)
 {
     return "prefork";
@@ -716,7 +735,7 @@ static int make_child(server_rec *s, int slot)
         apr_signal(SIGQUIT, SIG_DFL);
 #endif
         apr_signal(SIGTERM, sig_term);
-        ap_scoreboard_image->parent[slot].pid = getpid();
+        prefork_note_child_started(slot, getpid());
         child_main(slot);
         /* NOTREACHED */
     }
@@ -774,7 +793,7 @@ static int make_child(server_rec *s, int slot)
         child_main(slot);
     }
 
-    ap_scoreboard_image->parent[slot].pid = pid;
+    prefork_note_child_started(slot, pid);
 
     return 0;
 }
@@ -995,6 +1014,7 @@ static int prefork_run(apr_pool_t *_pconf, apr_pool_t *plog, server_rec *s)
             if (child_slot >= 0) {
                 (void) ap_update_child_status_from_indexes(child_slot, 0, SERVER_DEAD,
                                                            (request_rec *) NULL);
+                prefork_note_child_killed(child_slot, 0, 0);
                 if (processed_status == APEXIT_CHILDSICK) {
                     /* child detected a resource shortage (E[NM]FILE, ENOBUFS, etc)
                      * cut the fork rate to the minimum
diff --git a/server/mpm/winnt/mpm_winnt.c b/server/mpm/winnt/mpm_winnt.c
index 0d68ea3bc4..e819d863d7 100644
--- a/server/mpm/winnt/mpm_winnt.c
+++ b/server/mpm/winnt/mpm_winnt.c
@@ -139,6 +139,22 @@ AP_INIT_TAKE1("ThreadLimit", set_thread_limit, NULL, RSRC_CONF,
 { NULL }
 };
 
+static void winnt_note_child_started(int slot, pid_t pid)
+{
+    ap_scoreboard_image->parent[slot].pid = pid;
+    ap_run_child_status(ap_server_conf,
+                        ap_scoreboard_image->parent[slot].pid,
+                        my_generation, slot, MPM_CHILD_STARTED);
+}
+
+static void winnt_note_child_killed(int slot)
+{
+    ap_run_child_status(ap_server_conf,
+                        ap_scoreboard_image->parent[slot].pid,
+                        ap_scoreboard_image->parent[slot].generation,
+                        slot, MPM_CHILD_EXITED);
+    ap_scoreboard_image->parent[slot].pid = 0;
+}
 
 /*
  * Signalling Apache on NT.
@@ -767,7 +783,7 @@ static int master_main(server_rec *s, HANDLE shutdown_event, HANDLE restart_even
      * child at once.
      */
     ap_scoreboard_image->parent[0].quiescing = 0;
-    ap_scoreboard_image->parent[0].pid = child_pid;
+    winnt_note_child_started(/* slot */ 0, child_pid);
 
     /* Wait for shutdown or restart events or for child death */
     winnt_mpm_state = AP_MPMQ_RUNNING;
@@ -843,6 +859,9 @@ static int master_main(server_rec *s, HANDLE shutdown_event, HANDLE restart_even
         CloseHandle(event_handles[CHILD_HANDLE]);
         event_handles[CHILD_HANDLE] = NULL;
     }
+
+    winnt_note_child_killed(/* slot */ 0);
+
     if (restart_pending) {
         ++my_generation;
         ap_scoreboard_image->global->running_generation = my_generation;
diff --git a/server/mpm/worker/worker.c b/server/mpm/worker/worker.c
index 705451bd22..752679d458 100644
--- a/server/mpm/worker/worker.c
+++ b/server/mpm/worker/worker.c
@@ -372,9 +372,47 @@ static int worker_query(int query_code, int *result, apr_status_t *rv)
     return OK;
 }
 
-static void worker_note_child_killed(int childnum)
+static void worker_note_child_killed(int childnum, pid_t pid, ap_generation_t gen)
 {
-    ap_scoreboard_image->parent[childnum].pid = 0;
+    if (childnum != -1) { /* child had a scoreboard slot? */
+        ap_run_child_status(ap_server_conf,
+                            ap_scoreboard_image->parent[childnum].pid,
+                            ap_scoreboard_image->parent[childnum].generation,
+                            childnum, MPM_CHILD_EXITED);
+        ap_scoreboard_image->parent[childnum].pid = 0;
+    }
+    else {
+        ap_run_child_status(ap_server_conf, pid, gen, -1, MPM_CHILD_EXITED);
+    }
+}
+
+static void worker_note_child_started(int slot, pid_t pid)
+{
+    ap_scoreboard_image->parent[slot].pid = pid;
+    ap_run_child_status(ap_server_conf,
+                        ap_scoreboard_image->parent[slot].pid,
+                        retained->my_generation, slot, MPM_CHILD_STARTED);
+}
+
+static void worker_note_child_lost_slot(int slot, pid_t newpid)
+{
+    ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, ap_server_conf,
+                 "pid %" APR_PID_T_FMT " taking over scoreboard slot from "
+                 "%" APR_PID_T_FMT "%s",
+                 newpid,
+                 ap_scoreboard_image->parent[slot].pid,
+                 ap_scoreboard_image->parent[slot].quiescing ?
+                 " (quiescing)" : "");
+    ap_run_child_status(ap_server_conf,
+                        ap_scoreboard_image->parent[slot].pid,
+                        ap_scoreboard_image->parent[slot].generation,
+                        slot, MPM_CHILD_LOST_SLOT);
+    /* Don't forget about this exiting child process, or we
+     * won't be able to kill it if it doesn't exit by the
+     * time the server is shut down.
+     */
+    ap_register_extra_mpm_process(ap_scoreboard_image->parent[slot].pid,
+                                  ap_scoreboard_image->parent[slot].generation);
 }
 
 static const char *worker_get_name(void)
@@ -390,6 +428,11 @@ static void clean_child_exit(int code)
     if (pchild) {
         apr_pool_destroy(pchild);
     }
+
+    if (one_process) {
+        worker_note_child_killed(/* slot */ 0, 0, 0);
+    }
+
     exit(code);
 }
 
@@ -1344,7 +1387,7 @@ static int make_child(server_rec *s, int slot)
 
     if (one_process) {
         set_signals();
-        ap_scoreboard_image->parent[slot].pid = getpid();
+        worker_note_child_started(slot, getpid());
         child_main(slot);
         /* NOTREACHED */
     }
@@ -1390,19 +1433,11 @@ static int make_child(server_rec *s, int slot)
         /* This new child process is squatting on the scoreboard
          * entry owned by an exiting child process, which cannot
          * exit until all active requests complete.
-         * Don't forget about this exiting child process, or we
-         * won't be able to kill it if it doesn't exit by the
-         * time the server is shut down.
          */
-        ap_log_error(APLOG_MARK, APLOG_DEBUG, 0, ap_server_conf,
-                     "taking over scoreboard slot from %" APR_PID_T_FMT "%s",
-                     ap_scoreboard_image->parent[slot].pid,
-                     ap_scoreboard_image->parent[slot].quiescing ?
-                         " (quiescing)" : "");
-        ap_register_extra_mpm_process(ap_scoreboard_image->parent[slot].pid);
+        worker_note_child_lost_slot(slot, pid);
     }
     ap_scoreboard_image->parent[slot].quiescing = 0;
-    ap_scoreboard_image->parent[slot].pid = pid;
+    worker_note_child_started(slot, pid);
     return 0;
 }
 
@@ -1611,6 +1646,7 @@ static void perform_idle_server_maintenance(void)
 
 static void server_main_loop(int remaining_children_to_start)
 {
+    ap_generation_t old_gen;
     int child_slot;
     apr_exit_why_e exitwhy;
     int status, processed_status;
@@ -1640,7 +1676,7 @@ static void server_main_loop(int remaining_children_to_start)
                     ap_update_child_status_from_indexes(child_slot, i, SERVER_DEAD,
                                                         (request_rec *) NULL);
 
-                ap_scoreboard_image->parent[child_slot].pid = 0;
+                worker_note_child_killed(child_slot, 0, 0);
                 ap_scoreboard_image->parent[child_slot].quiescing = 0;
                 if (processed_status == APEXIT_CHILDSICK) {
                     /* resource shortage, minimize the fork rate */
@@ -1655,8 +1691,9 @@ static void server_main_loop(int remaining_children_to_start)
                     --remaining_children_to_start;
                 }
             }
-            else if (ap_unregister_extra_mpm_process(pid.pid) == 1) {
-                /* handled */
+            else if (ap_unregister_extra_mpm_process(pid.pid, &old_gen) == 1) {
+                worker_note_child_killed(-1, /* already out of the scoreboard */
+                                         pid.pid, old_gen);
 #if APR_HAS_OTHER_CHILD
             }
             else if (apr_proc_other_child_alert(&pid, APR_OC_REASON_DEATH,