Messages in this thread | | | Date | Tue, 16 Oct 2018 16:14:06 +0200 | From | Oleg Nesterov <> | Subject | Re: [PATCH] kernel/signal: Signal-based pre-coredump notification |
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On 10/15, Enke Chen wrote: > > > I don't understand why we need valid_predump_signal() at all. > > Most of the signals have well-defined semantics, and would not be appropriate > for this purpose.
you are going to change the rules anyway.
> That is why it is limited to only SIGCHLD, SIGUSR1, SIGUSR2.
Which do not queue. So the parent won't get the 2nd signal if 2 children crash at the same time.
> >> if (sig_kernel_coredump(signr)) { > >> + /* > >> + * Notify the parent prior to the coredump if the > >> + * parent is interested in such a notificaiton. > >> + */ > >> + int p_sig = current->real_parent->predump_signal; > >> + > >> + if (valid_predump_signal(p_sig)) { > >> + read_lock(&tasklist_lock); > >> + do_notify_parent_predump(current); > >> + read_unlock(&tasklist_lock); > >> + cond_resched(); > > > > perhaps this should be called by do_coredump() after coredump_wait() kills > > all the sub-threads? > > proc_coredump_connector(current) is located here, they should stay together.
Why?
Once again, other threads are still alive. So if the parent restarts the service after it recieves -predump_signal, the new process can "race" with the old thread.
Oleg.
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