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

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Message-ID: <20101216132710.73abf94d@suzukikp>
Date:	Thu, 16 Dec 2010 13:27:10 +0530
From:	"Suzuki K. Poulose" <suzuki@...ibm.com>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	Tejun Heo <tj@...nel.org>,
	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>,
	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 12:51:54 +0100
Andi Kleen <andi@...stfloor.org> wrote:

> > 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.
> 
> Why is it not safe for a signal?
> 
> From the kernel side it should be. glibc may do some funky things
> on fork, but you could always call the syscall directly.

I came across the following links,

http://sourceware.org/bugzilla/show_bug.cgi?id=4737
https://www.opengroup.org/austin/docs/austin_445.txt

which seem to suggest that fork() is not async-safe due to malloc and the  
fork handlers. But a direct fork syscall by-passing glibc should be safe.

Thanks
Suzuki

> 
> -Andi

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