On 02/16, Oleg Nesterov wrote:
>
> On 02/16, Mandeep Singh Baines wrote:
> >
> > +static int sigkill_pending(struct task_struct *tsk)
> > +{
> > + return signal_pending(tsk) &&
> > + (sigismember(&tsk->pending.signal, SIGKILL) ||
> > + sigismember(&tsk->signal->shared_pending.signal, SIGKILL));
> > +}
>
> Why? __fatal_signal_pending() is enough, you do not need to check
> ->shared_pending. And once again, ignoring the freezer problems I
> do not think we need this check at all.
>
> IOW. Yes, we will probably need to do this change but only to be
> freezer-friendly.
And, forgot to mention, this logic is not right in the multi-
threaded case. I mean, you can't assume that 'kill -9 dumpingtask"
will wake the coredumping thread up. So this sigkill_pending() or
__fatal_signal_pending() check can only work in the single-threaded
case.
> --- x/fs/coredump.c
> +++ x/fs/coredump.c
> @@ -416,17 +416,17 @@ static void wait_for_dump_helpers(struct
> pipe_lock(pipe);
> pipe->readers++;
> pipe->writers--;
> + // TODO: wake_up_interruptible_sync_poll ?
> + wake_up_interruptible_sync(&pipe->wait);
> + kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
> + pipe_unlock(pipe);
>
> - while ((pipe->readers > 1) && (!signal_pending(current))) {
> - wake_up_interruptible_sync(&pipe->wait);
> - kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
> - pipe_wait(pipe);
> - }
> + wait_event_freezekillable(&pipe->wait, pipe->readers == 1);
I tried to check (but didn't even try to test). I think this should
work. Assuming that we teach SIGKILL to actually kill the dumper, but
we need this in any case.
But. Then we need to change pipe_release() to use wake_up_sync_poll()
(which we do not have). Probably we can do this... but otoh if we protect
the dumping thread from the non-fatal signals (and again, we need this
anyway ;) then we can simply do wait_event_freezable().
Damn. I need to think more.
Oleg.
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