Messages in this thread | | | Date | Sat, 16 Feb 2013 20:46:43 +0100 | From | Oleg Nesterov <> | Subject | Re: [PATCH 5/5] coredump: ignore non-fatal signals when core dumping to a pipe |
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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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