linux-kernel - Re: Can we make application core dumps interruptible?

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Date:	Thu, 29 Nov 2007 15:01:19 +0300
From:	Oleg Nesterov <oleg@...sign.ru>
To:	Robin Holt <holt@....com>
Cc:	Roland McGrath <roland@...hat.com>, Kawai@...ricas.sgi.com,
	Hidehiro <hidehiro.kawai.ez@...achi.com>,
	Davide Libenzi <davidel@...ilserver.org>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Bron Nelson <bron@....com>, Stephen Champion <schamp@....com>,
	linux-kernel@...r.kernel.org
Subject: Re: Can we make application core dumps interruptible?

On 11/28, Robin Holt wrote:
> 
> We have a customer machine with 4096 cpus.  When some user applications
> crash, it begins dumping core and can tie up the filesystem and
> processors for a considerable period of time.  Often, they contact the
> user and the user says the core dump files will not be useful and they
> reboot the machine.  They have already reduced the default core dump size
> to not dump anything and taken all reasonable steps to limiting core dumps
> while still allowing them to be useful for those users that need them.
> They would like to not need to reboot.
> 
> They hoped for a couple changes, one of which is a way for a SIGTERM,
> SIGKILL, or something along that line interrupting the core dump process.
> Is this the correct direction to take?  Are there any better ideas for
> handling this?

Well, I don't know what would be the right soultion, but perhaps we can do
something like the patch below. Allows to abort the coredump with kill -9.

Oleg.

--- fs/binfmt_elf.c~	2007-10-25 16:22:10.000000000 +0400
+++ fs/binfmt_elf.c	2007-11-29 14:47:43.000000000 +0300
@@ -1178,6 +1178,9 @@ out:
  */
 static int dump_write(struct file *file, const void *addr, int nr)
 {
+	if (sigismember(&current->signal->shared_pending.signal, SIGKILL))
+		return 0;
+
 	return file->f_op->write(file, addr, nr, &file->f_pos) == nr;
 }
 

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