On 2022.04.28 14:46, Junio C Hamano wrote:
> Josh Steadmon <steadmon@xxxxxxxxxx> writes:
>
> > In rare cases, wait_or_whine() cannot determine a child process's exit
> > status (and will return -1 in this case). This can cause Git to issue
> > trace2 child_exit events despite the fact that the child is still
> > running.
>
> Rather, we do not even know if the child is still running when it
> happens, right?
Correct, if you'd like me to clarify the commit message I'll send a V2.
> It is curious what "rare cases" makes the symptom
> appear. Do we know?
Unfortunately, no. The quoted 80 million exit event instance was not
reproducible.
> The patch looks OK from the "we do not know the child exited in this
> case, so we shouldn't be reporting the child exit" point of view, of
> course. Having one event that started a child in the log and then
> having millions of events that reports the exit of the (same) child
> is way too broken. With this change, we remove these phoney exit
> events from the log.
>
> Do we know, for such a child process that caused these millions
> phoney exit events, we got a real exit event at the end?
We don't know. The trace log filled up the user's disk in this case, so
the log was truncated.
> Otherwise,
> we'd still have a similar problem in the opposite direction, i.e. a
> child has a start event recorded, many exit event discarded but the
> log lacks the true exit event for the child, implying that the child
> is still running because we failed to log its exit?
Yes, that is a weakness with this approach.
> > int finish_command_in_signal(struct child_process *cmd)
> > {
> > int ret = wait_or_whine(cmd->pid, cmd->args.v[0], 1);
> > - trace2_child_exit(cmd, ret);
> > + if (ret != -1)
> > + trace2_child_exit(cmd, ret);
> > return ret;
> > }
>
> Will queue; thanks.
Thanks, and sorry for the delayed reply, I've been out sick for a few
days.
