linux-kernel - Re: [Linux 2.6.29-rc2] BUG: using smp_processor

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Date:	Tue, 27 Jan 2009 16:49:46 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	Frédéric Weisbecker <fweisbec@...il.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Maciej Rutecki <maciej.rutecki@...il.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [Linux 2.6.29-rc2] BUG: using smp_processor_id() in preemptible


* Rafael J. Wysocki <rjw@...k.pl> wrote:

> > In fact whatever check you put in it's _always_ going to be 
> > fundamentally more fragile than direct instrumentation: you cannot 
> > possibly check all possible places that enable interrupts. (they could 
> > be disabling interrupts as a _restore_irqs() sequence for example)
> 
> In this particular case, I'm not really interested in that.  What I'm 
> interested in is which driver's ->suspend_late() or ->resume_early() (or 
> the equivalents for sysdevs) has enabled interrupts, which is quite easy 
> to check directly.

But this is exactly what it does - without any need for debug checks 
spread around!

You'll get a _full stack dump_ from the very driver that is enabling 
interrupts! You dont get a trace - you get a stack dump of the very place 
that is buggy. It does not get any better than that.

	Ingo
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