Messages in this thread | | | Date | Wed, 24 Oct 2018 15:52:13 +0200 | From | Oleg Nesterov <> | Subject | Re: [PATCH v2] kernel/signal: Signal-based pre-coredump notification |
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On 10/23, Enke Chen wrote: > > >> + /* > >> + * Send the pre-coredump signal to the parent if requested. > >> + */ > >> + read_lock(&tasklist_lock); > >> + notify = do_notify_parent_predump(current); > >> + read_unlock(&tasklist_lock); > >> + if (notify) > >> + cond_resched(); > > > > Hmm. I do not understand why do we need cond_resched(). And even if we need it, > > why we can't call it unconditionally? > > Remember the goal is to allow the parent (e.g., a process manager) to take early > action. The "yield" before doing coredump will help.
I don't see how can it actually help...
cond_resched() is nop if CONFIG_PREEMPT or should_resched() == 0.
and the coredumping thread will certainly need to sleep/wait anyway.
> > And once again, SIGCHLD/SIGUSR do not queue, this means that PR_SET_PREDUMP_SIG > > is pointless if you have 2 or more children. > > Hmm, could you point me to the code where SIGCHLD/SIGUSR is treated differently > w.r.t. queuing? That does not sound right to me.
see the legacy_queue() check. Any signal < SIGRTMIN do not queue. IOW, if SIGCHLD is already pending, then next SIGCHLD is simply ignored.
Oleg.
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