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Date: Tue, 27 Jan 2009 16:49:46 +0100
From: Ingo Molnar <mingo@elte.hu>
To: "Rafael J. Wysocki" <rjw@sisk.pl>
Cc: =?iso-8859-1?Q?Fr=E9d=E9ric?= Weisbecker <fweisbec@gmail.com>,
       Steven Rostedt <rostedt@goodmis.org>,
       Linus Torvalds <torvalds@linux-foundation.org>,
       Maciej Rutecki <maciej.rutecki@gmail.com>,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
       Andrew Morton <akpm@linux-foundation.org>,
       Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [Linux 2.6.29-rc2] BUG: using smp_processor_id() in preemptible
Message-ID: <20090127154946.GA28209@elte.hu>
References: <8db1092f0901170058k325dc6ddtddb42deea1ddd098@mail.gmail.com> <200901262148.49717.rjw@sisk.pl> <20090126213519.GB13670@elte.hu> <200901271628.54037.rjw@sisk.pl>
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* Rafael J. Wysocki <rjw@sisk.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