Re: [PATCH] exec: log when wait_for_dump_helpers aborts due to a signal

[Oleg Nesterov <oleg@redhat.com>]

On 10/28, Andrew Morton wrote:
>
> Well.  Neil's changelog for 61be228a06dc6e8662 is quite nice and tells
> us everything we could possibly want to know, except for why it tests
> sgnal_pending() :(

In short, signal_pending() should not be here. It only reflects the
fact that do_coredump() needs the fixes (and can't resist, I sent the
patch several years ago, but it was ignored ;)

There are 2 reasons. if signal_pending() == T then:

	- pipe_wait() is pointless, it won't block. We do not want
	  a busywait loop.

	- And probably even wait_for_dump_helpers() is pointless,
	  it is quite possible that pipe_write() already failed
	  before and the reader doesn't know this.

What I think we should do:

	- Fix this code, it should not react to signals.

	- But! at the same time the explicit SIGKILL should stop
	  the coredump. It can take a lot of time/resources.

	  This also makes it oom-killable, and this is important.

	- If we dump to the pipe, then perhaps it makes sense to
	  send a signal to the pipe reader in the latter case, but
	  this is a bit offtopic.

I'll try to redo my old patches for 3.2 once I have the time. There
are some nasty problems which I forgot, _iirc_ this is not that
trivial.

Oleg.