Date: Tue, 15 Mar 2005 10:28:06 +0100
From: Ingo Molnar <mingo@elte.hu>
To: Christoph Lameter <christoph@lameter.com>
Cc: Andrew Morton <akpm@osdl.org>, Oleg Nesterov <oleg@tv-sign.ru>,
       linux-kernel@vger.kernel.org, Shai Fultheim <Shai@Scalex86.org>
Subject: Re: [patch] del_timer_sync scalability patch
Message-ID: <20050315092806.GA28924@elte.hu>
References: <4231E959.141F7D85@tv-sign.ru> <42343C61.6A1210C0@tv-sign.ru> <Pine.LNX.4.58.0503150004190.13281@server.graphe.net>
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* Christoph Lameter <christoph@lameter.com> wrote:

> The following patch removes the magic in the timer_list structure
> (Andrew suggested that we may not need it anymore) and replaces it
> with two u8 variables that give us some additional state of the timer

The 'remove the magic' observation is not a 'backdoor' to introduce new
fields 'for free'. So please dont mix the two things into one patch.

> +       u8 running;             /* function is currently executing */
> +       u8 shutdown;            /* do not schedule this timer */

it may as well be cleaner to do the timer->base_running thing after all,
and to do this in __run_timers():

	timer->base = NULL;
	timer->base_running = base;

note that we cannot clear ->base_running in __run_timers() [we dont own
any access to the timer anymore, it may be kfree()d, etc.], so
del_timer_sync() has to make sure that the timer->base_running info is
not stale - it is a hint only. But it looks doable, and it should solve
the NUMA scalability problem.

	Ingo
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