linux-kernel - Re: [RFC][PATCH 0/5] Signal scalability series

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Message-ID: <20111004173936.GC3489@redhat.com>
Date:	Tue, 4 Oct 2011 19:39:36 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	Matt Fleming <matt@...sole-pimps.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andi Kleen <andi@...stfloor.org>, Tejun Heo <tj@...nel.org>,
	linux-kernel@...r.kernel.org, Tony Luck <tony.luck@...el.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	David Mosberger-Tang <davidm@...uge.net>
Subject: Re: [RFC][PATCH 0/5] Signal scalability series

On 10/04, Thomas Gleixner wrote:
>
> The main nuisance of sighand->siglock is the exit race protection and
> that's why we need to take it for evrything and some more.
>
> In order to distangle the posix-(cpu)-timer and other stuffs
> protection from that single lock, you need to introduce "independent"
> locks

Yes. And there is another (much more important imho) reason.

We need a separate lock to protect thread_group/children to avoid
tasklist_lock in exit_notify/wait/etc. And probably it should be
sleepable.

Oleg.

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