linux-kernel - Re: [PATCH] fix BUG using smp_processor_id() in touch_nmi_watchdog and touch_softlockup

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Date:	Thu, 26 Aug 2010 13:14:31 +0300
From:	Maxim Levitsky <maximlevitsky@...il.com>
To:	Don Zickus <dzickus@...hat.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Len Brown <len.brown@...el.com>,
	Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
	Yong Zhang <yong.zhang0@...il.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org,
	linux-acpi@...r.kernel.org, Andy Grover <andy.grover@...cle.com>
Subject: Re: [PATCH] fix BUG using smp_processor_id() in touch_nmi_watchdog
 and touch_softlockup_watchdog

On Thu, 2010-08-19 at 22:57 -0400, Don Zickus wrote: 
> On Wed, Aug 18, 2010 at 01:01:56PM -0700, Andrew Morton wrote:
> > The surprise new requirement that touch_nmi_watchdog() be called from
> > non-preemptible code does seem to make sense IMO.  It's hard to see why
> > anyone would be touching the watchdog unless he's spinning in irqs-off
> > code.  Except, of course, when we have a utility function which can be
> > called from wither irqs-on or irqs-off: acpi_os_stall().
> > 
> > That being said, it's not good to introduce new API requirements by
> > accident!  An audit of all callers should first be performed, at least.
> > 
> > 
> > The surprise new requirement that touch_softlockup_watchdog() be called
> > from non-preemptible code doesn't make sense IMO.  If I have a piece of
> > code in the kernel which I expect to sit in TASK_UNINTERRUPTIBLE state
> > for three minutes waiting for my egg to boil, I should be able to do
> > that and I should be able to touch the softlockup detector without
> > needing to go non-preemptible.
> 
> Ok, so here is my patch that syncs the touch_*_watchdog back in line with
> the old semantics.  Hopefully this will undo any harm I caused.

Was this patch forgotten?

Best regards,
Maxim Levitsky

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