Mailing List Archive

On 4/14/22 4:38 PM, ylavic@apache.org wrote:
> Author: ylavic
> Date: Thu Apr 14 14:38:03 2022
> New Revision: 1899858
>
> URL: http://svn.apache.org/viewvc?rev=1899858&view=rev
> Log:
> mpm_event: Handle children killed pathologically.
>
> If children processes get killed (SIGSEGV/SIGABRT/..) early after starting or
> frequently enough then we never enter perform_idle_server_maintenance() to
> try something.
>
> Below three successive children killed restart them immediately, above three
> let's sleep the usual 1s (to avoid fork()s flood) and do the idle maintenance.
>
>
> Modified:
> httpd/httpd/trunk/server/mpm/event/event.c
>
> Modified: httpd/httpd/trunk/server/mpm/event/event.c
> URL: http://svn.apache.org/viewvc/httpd/httpd/trunk/server/mpm/event/event.c?rev=1899858&r1=1899857&r2=1899858&view=diff
> ==============================================================================
> --- httpd/httpd/trunk/server/mpm/event/event.c (original)
> +++ httpd/httpd/trunk/server/mpm/event/event.c Thu Apr 14 14:38:03 2022
> @@ -3382,6 +3382,7 @@ static void server_main_loop(int remaini
> {
> int num_buckets = retained->mpm->num_buckets;
> int max_daemon_used = 0;
> + int successive_signals = 0;
> int child_slot;
> apr_exit_why_e exitwhy;
> int status, processed_status;
> @@ -3460,11 +3461,31 @@ static void server_main_loop(int remaini
> /* Don't perform idle maintenance when a child dies,
> * only do it when there's a timeout. Remember only a
> * finite number of children can die, and it's pretty
> - * pathological for a lot to die suddenly.
> + * pathological for a lot to die suddenly. If that happens
> + * anyway, protect against fork()+kill() flood by not restarting
> + * more than 3 children if no timeout happened in between,
> + * otherwise we keep going with idle maintenance.
> */
> - continue;
> + if (child_slot < 0 || !APR_PROC_CHECK_SIGNALED(exitwhy)) {
> + continue;
> + }
> + if (++successive_signals >= 3) {
> + if (successive_signals % 10 == 3) {
> + ap_log_error(APLOG_MARK, APLOG_WARNING, 0,
> + ap_server_conf, APLOGNO(10392)
> + "children are killed successively!");
> + }
> + apr_sleep(apr_time_from_sec(1));

Why do we need the sleep here? Why can't we just do continue?

> + }
> + else {
> + ++remaining_children_to_start;
> + }
> + }
> + else {
> + successive_signals = 0;
> }
> - else if (remaining_children_to_start) {
> +
> + if (remaining_children_to_start) {
> /* we hit a 1 second timeout in which none of the previous
> * generation of children needed to be reaped... so assume
> * they're all done, and pick up the slack if any is left.
>
>
>

Regards

Rüdiger