Hi,
to reproduce it, I start httpd-2.4.4 like this:
/usr/sbin/httpd -k start -DFOREGROUND
and in another terminal I run ab like this:
ab -n 150000 -c 4 http://127.0.0.1/index.php
Index.php is just dummy script with phpinfo.
When "ab" is benchmarking, I kill httpd using "ctrl+c". In 4/10 tries it
crashes with following backtrace [1].
If gdb does not lie, there is race condition in signal handling. I'm not
sure if anything changed in this code between 2.2 and 2.4, but it looks
like 2.2 was handling this situation somehow better. I think this
situation can lead to various problems like deadlocks.
I've been able to workaround this using the attached patch, but I don't
think this is the best way how to fix this problem. It would be better
to find out why there are more signals called in a row as a result of
single SIGINT signal sent to main process.
I will try to do that myself, but I was thinking there could be people
more familiar with this part of code and with httpd's children lifecycle
reading this list.
[1]
#0 0x00007fe74b7d2ba5 in raise () from /lib64/libc.so.6
#1 0x00007fe74b7d4358 in abort () from /lib64/libc.so.6
#2 0x00007fe74b81259b in __libc_message () from /lib64/libc.so.6
#3 0x00007fe74b819a8e in _int_free () from /lib64/libc.so.6
#4 0x00007fe74bf8e85c in allocator_free (node=0x7fe74bb4e798
<main_arena+88>, allocator=0x7fe74e7ab670) at memory/unix/apr_pools.c:430
#5 apr_pool_destroy (pool=0x7fe74e7ab768) at memory/unix/apr_pools.c:856
#6 0x00007fe74308c1be in clean_child_exit (code=code@entry=0) at
prefork.c:218
#7 0x00007fe74308c9cb in just_die (sig=<optimized out>) at prefork.c:344
#8 <signal handler called>
#9 0x00007fe74d06d541 in _dl_fini () from /lib64/ld-linux-x86-64.so.2
#10 0x00007fe74b7d5df1 in __run_exit_handlers () from /lib64/libc.so.6
#11 0x00007fe74b7d5e75 in exit () from /lib64/libc.so.6
#12 0x00007fe74308c1db in clean_child_exit (code=code@entry=0) at
prefork.c:227
#13 0x00007fe74308c5f5 in child_main
(child_num_arg=child_num_arg@entry=2) at prefork.c:725
#14 0x00007fe74308c94c in make_child (s=0x7fe74e5a5368,
slot=slot@entry=2) at prefork.c:800
#15 0x00007fe74308c9a6 in startup_children (number_to_start=3) at
prefork.c:818
#16 0x00007fe74308d856 in prefork_run (_pconf=<optimized out>,
plog=0x7fe74e5d74f8, s=0x7fe74e5a5368) at prefork.c:976
#17 0x00007fe74d2a5d4e in ap_run_mpm ()
#18 0x00007fe74d29f3fa in main ()
Thanks for help,
Jan Kaluza
diff --git a/server/mpm/prefork/prefork.c b/server/mpm/prefork/prefork.c
index ae0fd37..cc7632d 100644
--- a/server/mpm/prefork/prefork.c
+++ b/server/mpm/prefork/prefork.c
@@ -212,6 +212,10 @@ static void prefork_note_child_started(int slot, pid_t pid)
static void clean_child_exit(int code) __attribute__ ((noreturn));
static void clean_child_exit(int code)
{
+ if (mpm_state == AP_MPMQ_STOPPING) {
+ exit(code);
+ }
+
mpm_state = AP_MPMQ_STOPPING;
if (pchild) {
@@ -341,6 +345,8 @@ static const char *prefork_get_name(void)
static void just_die(int sig)
{
+ apr_signal(SIGHUP, 0);
+ apr_signal(SIGTERM, 0);
clean_child_exit(0);
}
