Re: [PATCH 5/5] coredump: abort core dump piping only due to afatal signal

From: Oleg Nesterov
Date: Fri Feb 15 2013 - 10:02:38 EST

On 02/14, Mandeep Singh Baines wrote:
> This patch makes wait_for_dump_helpers() not to abort piping the core
> dump data when the crashing process has received any but a fatal signal
> (SIGKILL). The rationale is that a crashing process may still receive
> uninteresting signals such as SIGCHLD when its core dump data is being
> redirected to a helper application.

You already sent this change in the past ;) and I already reviewed it.

It is not enough and imho not good. Damn, I'll try very much to make the
patches on weekend...

> - while ((pipe->readers > 1) && (!signal_pending(current))) {
> + while ((pipe->readers > 1) && (!fatal_signal_pending(current))) {

This turns pipe_wait() belowe into the busy-wait loop if signal_pending().
Not good. And not enough, there are other reasons why coredump can fail
if the signal is pending.

> wake_up_interruptible_sync(&pipe->wait);
> kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
> pipe_wait(pipe);
> + pipe_unlock(pipe);
> + try_to_freeze();

Oh, yes. One of the problems with coredump/signals is freezer. Not sure
what should we do...

But if we add try_to_freeze() here, we need to add more try_to_freeze's,
think about dumping the huge core on the slow media.


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