worker MPM: Fix a problem which could cause httpd processes to

remain active after shutdown.

The problem occurred when a scoreboard entry currently
in use by an exiting child process was used for a new child
process.  At that point, the MPM forgot about the exiting
child process, so ap_reclaim_child_processes() wouldn't be
able to forceably terminate it.

(An exiting child process may *never* exit due to a stuck
or long-running request being handled on one of the threads.)


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@109510 13f79535-47bb-0310-9956-ffa450edef68

1 files changed, 32 insertions, 1 deletions

diff --git a/include/mpm_common.h b/include/mpm_common.h
index 85a4db5606..e10f840c3d 100644
--- a/include/mpm_common.h
+++ b/include/mpm_common.h
@@ -59,7 +59,7 @@ extern "C" {
  * Make sure all child processes that have been spawned by the parent process
  * have died.  This includes process registered as "other_children".
  * @warning This is only defined if the MPM defines 
- *          MPM_NEEDS_RECLAIM_CHILD_PROCESS
+ *          AP_MPM_WANT_RECLAIM_CHILD_PROCESSES
  * @param terminate Either 1 or 0.  If 1, send the child processes SIGTERM
  *        each time through the loop.  If 0, give the process time to die
  *        on its own before signalling it.
@@ -67,12 +67,43 @@ extern "C" {
  *  MPM_CHILD_PID -- Get the pid from the specified spot in the scoreboard
  *  MPM_NOTE_CHILD_KILLED -- Note the child died in the scoreboard
  * </pre>
+ * @tip The MPM child processes which are reclaimed are those listed
+ * in the scoreboard as well as those currently registered via
+ * ap_register_extra_mpm_process().
  */
 #ifdef AP_MPM_WANT_RECLAIM_CHILD_PROCESSES
 void ap_reclaim_child_processes(int terminate);
 #endif
 
 /**
+ * Tell ap_reclaim_child_processes() about an MPM child process which has no
+ * entry in the scoreboard.
+ * @warning This is only defined if the MPM defines
+ *          AP_MPM_WANT_RECLAIM_CHILD_PROCESSES
+ * @param pid The process id of an MPM child process which should be
+ * reclaimed when ap_reclaim_child_processes() is called.
+ * @tip If an extra MPM child process terminates prior to calling
+ * ap_reclaim_child_processes(), remove it from the list of such processes
+ * by calling ap_unregister_extra_mpm_process().
+ */
+#ifdef AP_MPM_WANT_RECLAIM_CHILD_PROCESSES
+void ap_register_extra_mpm_process(pid_t pid);
+#endif
+
+/**
+ * Unregister an MPM child process which was previously registered by a
+ * call to ap_register_extra_mpm_process().
+ * @warning This is only defined if the MPM defines
+ *          AP_MPM_WANT_RECLAIM_CHILD_PROCESSES
+ * @param pid The process id of an MPM child process which no longer needs to
+ * be reclaimed.
+ * @return 1 if the process was found and removed, 0 otherwise
+ */
+#ifdef AP_MPM_WANT_RECLAIM_CHILD_PROCESSES
+int ap_unregister_extra_mpm_process(pid_t pid);
+#endif
+
+/**
  * Determine if any child process has died.  If no child process died, then
  * this process sleeps for the amount of time specified by the MPM defined
  * macro SCOREBOARD_MAINTENANCE_INTERVAL.