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SubjectRe: [PATCH] kernel/signal: Signal-based pre-coredump notification
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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