Date: Wed, 15 Dec 2010 16:56:26 +0530
From: "Suzuki K. Poulose" <suzuki@in.ibm.com>
To: Tejun Heo <tj@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
        linux-kernel@vger.kernel.org,
        Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>,
        Christoph Hellwig <hch@lst.de>, Masami Hiramatsu <mhiramat@redhat.com>,
        Ananth N Mavinakayanahalli <ananth@in.ibm.com>,
        Daisuke HATAYAMA <d.hatayama@jp.fujitsu.com>,
        Andi Kleen <andi@firstfloor.org>, Roland McGrath <roland@redhat.com>,
        Amerigo Wang <amwang@redhat.com>,
        KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
        KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
        Oleg Nesterov <oleg@redhat.com>,
        Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [RFC] [Patch 0/21] Non disruptive application core dump
 infrastructure
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On Wed, 15 Dec 2010 10:37:48 +0100
Tejun Heo <tj@kernel.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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