linux-kernel - Re: [RFC] [Patch 0/21] Non disruptive application core dump infrastructure

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Message-ID: <20101215165626.715007b5@suzukikp>
Date:	Wed, 15 Dec 2010 16:56:26 +0530
From:	"Suzuki K. Poulose" <suzuki@...ibm.com>
To:	Tejun Heo <tj@...nel.org>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel@...r.kernel.org,
	Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>,
	Christoph Hellwig <hch@....de>,
	Masami Hiramatsu <mhiramat@...hat.com>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Daisuke HATAYAMA <d.hatayama@...fujitsu.com>,
	Andi Kleen <andi@...stfloor.org>,
	Roland McGrath <roland@...hat.com>,
	Amerigo Wang <amwang@...hat.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Oleg Nesterov <oleg@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [RFC] [Patch 0/21] Non disruptive application core dump
 infrastructure

On Wed, 15 Dec 2010 10:37:48 +0100
Tejun Heo <tj@...nel.org> wrote:

> Hello, Suzuki.
> 
> On 12/15/2010 06:34 AM, Suzuki K. Poulose wrote:
> > I'd be very glad not using the freezer if there is a neat way to
> > accomplish this without the undesired side effects. Tejun's ptrace
> > enhancement would still require a userland program to control
> > it(gcore); something contained in the kernel would be ideal.
> 
> Why is using gcore a bad thing?  If we make ptrace avoid the implicit
> SIGSTOP, the side effects of ptrace would be the same as using freezer
> but with the benefit that it's properly integrated to the process
> model and job control.

The advantages of the new approach are :

1) A process can trigger a core synchronously, upon an event, say a signal 
handler and continue from there. gcore would require a fork(), which is not 
safe to use from a signal handler.

2) We can seek to only the data we need

Thanks
Suzuki

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