linux-kernel - Re: [PATCH] sysrq: freeze other CPUs during sysrq-t

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Message-ID: <7b97a12b0808201528o5bab7840w1226d1faadb2c924@mail.gmail.com>
Date:	Wed, 20 Aug 2008 19:28:37 -0300
From:	"Gary Shi" <garyu.shi@...il.com>
To:	"Jeremy Fitzhardinge" <jeremy@...p.org>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] sysrq: freeze other CPUs during sysrq-t

On 8/16/08, Jeremy Fitzhardinge <jeremy@...p.org> wrote:
> Why not use stop_machine()?

Just know about  stop_machine() from your reply. Thanx. But after
checking its src, I feel its too demanding to fit sysrq-t use; e.g.,
when other cpus got deadlocked on some spin locks with preempt
disabled, then the kernel threads of stopmachine won't get a chance to
run on other cpus.

We would expect one or more cpus response only to irqs, when we try to
collect sysrq data; most of the  time, only when the systems hang for
whatever reasons does the sysrq data need to be collected, right?

--gys
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