linux-kernel - Re: [RESEND] proc, coredump: add CoreDumping flag to /proc/pid/status

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Message-ID: <20170922171826.GA1712@castle.DHCP.thefacebook.com>
Date:   Fri, 22 Sep 2017 10:18:26 -0700
From:   Roman Gushchin <guro@...com>
To:     Konstantin Khlebnikov <koct9i@...il.com>
CC:     Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Ingo Molnar <mingo@...nel.org>, <kernel-team@...com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Oleg Nesterov <oleg@...hat.com>
Subject: Re: [RESEND] proc, coredump: add CoreDumping flag to /proc/pid/status

On Fri, Sep 22, 2017 at 06:44:12PM +0300, Konstantin Khlebnikov wrote:
> On Thu, Sep 21, 2017 at 2:06 AM, Roman Gushchin <guro@...com> wrote:
> > Right now there is no convenient way to check if a process is being
> > coredumped at the moment.
> >
> > It might be necessary to recognize such state to prevent killing
> > the process and getting a broken coredump.
> > Writing a large core might take significant time, and the process
> > is unresponsive during it, so it might be killed by timeout,
> > if another process is monitoring and killing/restarting
> > hanging tasks.
> >
> > To provide an ability to detect if a process is in the state of
> > being coreduped, we can expose a boolean CoreDumping flag
> > in /proc/pid/status.
> 
> Makes sense.
> 
> Maybe print this line only when task actually makes dump?

I don't think we do this trick with any other fields...

> And probably expose pid of coredump helper.

It will be racy in most cases, so I'm not sure it worth it.
What's the usecase?
In any case, it sounds like a separate feature.

> 
> Add Oleg into CC.

Thank you!