On 7/25/12 1:08 PM, Chet Ramey wrote:
> On 7/25/12 11:33 AM, Andreas Schwab wrote:
>
>> I cannot see how CHILD_MAX is related to pid reuse. CHILD_MAX is a
>> per-user limit, but the pid namespace is global. If the shell forks a
>> new process, and the pid of it matches one of the previously used pids
>> for asynchronous jobs it can surely discard the remembered status for
>> that job.
>
> Thanks, that's a good restatement of the problem. Your proposed solution
> is one of the possibles. The question is whether or not it's necessary
> (apparently on some systems) and sufficient (probably).
OK, we have some data, we have a hypothesis, and we have a way to test it.
Let's test it.
Michael, please apply the attached patch, disable RECYCLES_PIDS, and run
your tests again. This makes the check for previously-saved exit statuses
unconditional.
Let's see if this is the one change of significance.
Chet
--
``The lyf so short, the craft so long to lerne.'' - Chaucer
``Ars longa, vita brevis'' - Hippocrates
Chet Ramey, ITS, CWRU [email protected] http://cnswww.cns.cwru.edu/~chet/
*** ../bash-4.2-patched/jobs.c 2011-01-07 10:59:29.000000000 -0500
--- jobs.c 2012-07-26 10:53:53.000000000 -0400
***************
*** 1900,1903 ****
--- 1902,1908 ----
delete_old_job (pid);
+ #if 0
+ /* Perform the check for pid reuse unconditionally. Some systems reuse
+ PIDs before giving a process CHILD_MAX/_SC_CHILD_MAX unique ones. */
#if !defined (RECYCLES_PIDS)
/* Only check for saved status if we've saved more than CHILD_MAX
***************
*** 1905,1908 ****
--- 1910,1914 ----
if ((js.c_reaped + bgpids.npid) >= js.c_childmax)
#endif
+ #endif
bgp_delete (pid); /* new process, discard any saved status */
