linux-kernel - Re: clocksource: !keventd_up() && schedule

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Message-ID: <4AAE0CC2.5010502@gmail.com>
Date:	Mon, 14 Sep 2009 11:28:34 +0200
From:	Jiri Slaby <jirislaby@...il.com>
To:	Thomas Gleixner <tglx@...utronix.de>
CC:	Linux kernel mailing list <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: clocksource: !keventd_up() && schedule_work() == oops

On 09/09/2009 10:00 AM, Jiri Slaby wrote:
> Hi,
> 
> I started to see oopses on boot in qemu machine because keventd is
> created in kernel_init/do_basic_setup, but schedule_work is done earlier
> in kernel_init/smp_init[1] when the tsc is unstable during this early phase.
> 
> It looks like "clocksource: Resolve cpu hotplug dead lock with TSC
> unstable" is the culprit.
> 
> Creating its own either singlethread or "multithread" workqueue won't
> work either (we do not have singlethread_cpu and cpu_populated_map).
> Checking !keventd_up() in the clocksource code looks to me like a hack.
> Any ideas, please?

Still present in mmotm 2009-09-14-01-57.

> [1]
> kernel_init/smp_init/cpu_up/native_cpu_up/check_tsc_sync_source/mark_tsc_unstable/clocksource_mark_unstable/__clocksource_unstable

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