linux-kernel - Re: [PATCH 2/2] posix-cpu-timers: use ->sighand instead of ->signal to check the task is alive

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Message-Id: <1233746479.5076.6.camel@laptop>
Date:	Wed, 04 Feb 2009 12:21:19 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>, Lin Ming <ming.m.lin@...el.com>,
	Roland McGrath <roland@...hat.com>,
	"Zhang, Yanmin" <yanmin_zhang@...ux.intel.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] posix-cpu-timers: use ->sighand instead of
 ->signal to check the task is alive

On Wed, 2009-02-04 at 00:17 +0100, Oleg Nesterov wrote:
> Sadly, it is not trivial to audit kernel/posix-cpu-timers.c, but it really
> abuses tasklist_lock. I believe it doesn't need this lock at all, but the
> changes are not easy to test.

It uses that to hold of task reaping so ->signal doesn't go away.

If we make ->signal refcountable, and rcu freed along with the tasks I
think we can get away without tasklist_lock.

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