linux-kernel - Re: Hang on 8-way with 2.6.23-rc2-rt2

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Message-Id: <1186507677.21381.191.camel@ghaskins-t60p.haskins.net>
Date:	Tue, 07 Aug 2007 13:27:57 -0400
From:	Gregory Haskins <ghaskins@...ell.com>
To:	Daniel Walker <dwalker@...sta.com>
Cc:	Ingo Molnar <mingo@...e.hu>, linux-rt-users@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: Hang on 8-way with 2.6.23-rc2-rt2

On Tue, 2007-08-07 at 10:03 -0700, Daniel Walker wrote:

> Could you drop the following config options and test again?
> 
> #
> # Processor type and features
> #
> CONFIG_TICK_ONESHOT=y
> CONFIG_NO_HZ=y
> CONFIG_HIGH_RES_TIMERS=y
> 

Will do.

I have a patch which works around the issue too, which I will forward
momentarily.  It appears as though there is a deadlock either between
two task_rq_locks, or between a task_rq_lock and something else.  The
patch I wrote changes the "double_lock_balance()" function to a full DP
algorithm under contention.  Technically I think the original
implementation was correct which is why my patch is really a workaround:
I think its just plastering over the real issue.  But in any case, the
8-way system is no longer slow and no longer nmi_watchdog/softlockups on
me(*).  Perhaps it will at least help in finding the root cause.

Regards,
-Greg

(*) There are still issues on the 8-way once we get passed this
scheduler problem, however.

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