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From Aaron Bannert <aa...@clove.org>
Subject Re: daedalus is running 2.0.31
Date Fri, 01 Feb 2002 15:59:42 GMT
On Fri, Feb 01, 2002 at 10:20:09AM -0500, Greg Ames wrote:
 
> yep.  It ran for nearly 5 hours.  Then the clock struck midnight, a cron job
> kicked off a graceful restart, and:

...all the horses turned back into mice... ;)


> [Fri Feb 01 00:00:04 2002] [notice] Apache/2.0.31 (Unix) configured -- resuming
> normal operations
> [Fri Feb 01 00:00:04 2002] [notice] seg fault or similar nasty error detected in
> the parent process
> 
> ...and we were down until I woke up, took a look, momentarily panicked, then put
> us back on 2.0.29 at Friday Feb 01 05:18:04 daedalus time.
> 
> At least we have a both a log message and a coredump now.  That wasn't the case
> not too long ago.  The dump is /usr/local/apache2.0.31/corefiles/httpd.core.1 . 
> The backtrace is pretty simple:
> 
> #0  0x806fdeb in find_child_by_pid (pid=0xbfbffa4c) at scoreboard.c:355
> #1  0x8063e9a in ap_mpm_run (_pconf=0x8099010, plog=0x80bf010, s=0x809a8d8)
>     at prefork.c:1078
> #2  0x8069676 in main (argc=1, argv=0xbfbffb30) at main.c:498
> #3  0x805d95d in _start ()

I have a feeling the scoreboard is getting destroyed by it's pool cleanup
routine before this routine gets called:

(gdb) p ap_scoreboard_image->parent
$2 = (process_score *) 0x2823500c
(gdb) p i
$3 = 0
(gdb) p ap_scoreboard_image->parent[0]
Cannot access memory at address 0x2823500c.

Did we intend to reuse the scoreboard across restarts, or recreate it?

It looks like the scoreboard is currently being created in the pconf
pool, which is cleared shortly after ap_run_mpm() decides to do a graceful.
OTOH, we don't call ap_run_pre_mpm() to create the scoreboard if we are
doing a graceful restart. I think that's where the SEGV is comming from.

-aaron

BTW, if we're ok to recreate during restart, I think this would fix prefork
(untested):

Index: server/mpm/prefork/prefork.c
===================================================================
RCS file: /home/cvs/httpd-2.0/server/mpm/prefork/prefork.c,v
retrieving revision 1.236
diff -u -u -r1.236 prefork.c
--- server/mpm/prefork/prefork.c    30 Jan 2002 22:35:56 -0000  1.236
+++ server/mpm/prefork/prefork.c    1 Feb 2002 15:57:38 -0000
@@ -1000,10 +1000,8 @@
     }
 
     SAFE_ACCEPT(accept_mutex_init(pconf));
-    if (!is_graceful) {
-        if (ap_run_pre_mpm(pconf, SB_SHARED) != OK) {
-            return 1;
-        }
+    if (ap_run_pre_mpm(pconf, SB_SHARED) != OK) {
+        return 1;
     }
 #ifdef SCOREBOARD_FILE
     else {


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