linux-kernel - Re: [PATCH -mm] extend sysrq-p functionality to cover all CPUs

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Message-ID: <20080310093024.55a4ff90@bree.surriel.com>
Date:	Mon, 10 Mar 2008 09:30:24 -0400
From:	Rik van Riel <riel@...riel.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	linux-kernel@...r.kernel.org, lwoodman@...hat.com
Subject: Re: [PATCH -mm] extend sysrq-p functionality to cover all CPUs

On Sun, 9 Mar 2008 22:47:59 -0700
Andrew Morton <akpm@...ux-foundation.org> wrote:

> On Sun, 9 Mar 2008 22:14:58 -0400 Rik van Riel <riel@...riel.com> wrote:
> 
> > SysRP-P is not all that useful on SMP systems, since the sysrq
> > irq rarely ends up on the CPU that we actually want to investigate.

> Doesn't everyone have a copy of this somewhere? ;)

Yes, but the old version of the patch calls on_each_cpu from
sysrq context, which is illegal since it could cause a deadlock.

> However it does have the downside that info can scroll away on large cpu
> counts.  Maybe it should be a new sysrq command?

It used to be sysrq-w in the patches that everybody has, but that
letter got taken for sysrq_showstate_blocked_op.

Only sysrq h, j, l, y and z are still free.  H is needed for help,
leaving just j, l, y and z.

I can see your point about overflowing the screen, however just
sysrq-p seems like a waste to have because it will probably not
print anything useful on a large CPU system...

If you still want it to be a separate letter, just let me know
which one of the last four I should take.

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