linux-kernel - Re: [PATCH -mm] coredump: format_corename: don't append .%pid if multi-threaded

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Date:	Tue, 22 Jul 2008 14:47:56 +0200
From:	"Michael Kerrisk" <mtk.manpages@...glemail.com>
To:	"Oleg Nesterov" <oleg@...sign.ru>
Cc:	"Alan Cox" <alan@...rguk.ukuu.org.uk>,
	"Roland McGrath" <roland@...hat.com>, akpm@...ux-foundation.org,
	linux-kernel@...r.kernel.org, andi@...stfloor.org
Subject: Re: [PATCH -mm] coredump: format_corename: don't append .%pid if multi-threaded

On Tue, Jul 22, 2008 at 2:43 PM, Oleg Nesterov <oleg@...sign.ru> wrote:
> On 07/22, Michael Kerrisk wrote:
>>
>> On Tue, Jul 22, 2008 at 2:18 PM, Oleg Nesterov <oleg@...sign.ru> wrote:
>> > If the coredumping is multi-threaded, format_corename() appends .%pid
>> > to the corename. This was needed before the proper multi-thread core
>> > dump support, now all the threads in the mm go into a single unified
>> > core file.
>> >
>> > Remove this special case, it is not even documented and we have "%p"
>> > and core_uses_pid.
>>
>> Hi Oleg,
>>
>> I have not thought about this at any length, but one question that
>> jumps to mind: could this feature still be useful for LinuxThreads,
>> where each thread does indeed have a separate PID?
>
> As far as I know, LinuxThreads use CLONE_VM, right?

Yes.

> The coredump will create the single core file for all processes because
> they have the same ->mm, the "threads" won't dump all over each other.

Yes, looks like you are right.  I had this vague idea that there were
circumstances where a dump of a LinuxThreads m-t process could produce
multipl core files, distinguished by the .PID, but I think I must have
misremembered.

> And, just in case, this patch doesn't make any difference if core_uses_pid
> is set or pid_in_pattern is true.
>
> That said, this is the user-visible change...

True.  Not sure how important that is in this case though.  What is
the reason for making this change (other than tidiness)?

-- 
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
man-pages online: http://www.kernel.org/doc/man-pages/online_pages.html
Found a bug? http://www.kernel.org/doc/man-pages/reporting_bugs.html
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