linux-kernel - Re: Suspend on Dell D420

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Message-Id: <20060804151758.1d3dd6bd.akpm@osdl.org>
Date:	Fri, 4 Aug 2006 15:17:58 -0700
From:	Andrew Morton <akpm@...l.org>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	"Steinar H. Gunderson" <sgunderson@...foot.com>,
	linux-kernel@...r.kernel.org
Subject: Re: Suspend on Dell D420

On Fri, 4 Aug 2006 23:27:38 +0200
"Rafael J. Wysocki" <rjw@...k.pl> wrote:

> On Friday 04 August 2006 18:23, Steinar H. Gunderson wrote:
> > [Please Cc me on any followups]
> > 
> > Hi,
> > 
> > Suspend-to-RAM works fine on my new Dell Latitude D420 (with Core Duo) in
> > 2.6.16, but it broke in 2.6.17 -- the machine suspends just fine, but when it
> > resumes, the disk never spins up, the screen stays black and it just hangs.
> > Bisecting shows that the following commit is where it broke:
> > 
> > commit 78eef01b0fae087c5fadbd85dd4fe2918c3a015f
> > Author: Andrew Morton <akpm@...l.org>
> > Date:   Wed Mar 22 00:08:16 2006 -0800
> >  
> >     [PATCH] on_each_cpu(): disable local interrupts
> >  
> >     When on_each_cpu() runs the callback on other CPUs, it runs with local
> >     interrupts disabled.  So we should run the function with local interrupts
> >     disabled on this CPU, too.
> >  
> >     And do the same for UP, so the callback is run in the same environment on both
> >     UP and SMP.  (strictly it should do preempt_disable() too, but I think
> >     local_irq_disable is sufficiently equivalent).
> >  
> >     Also uninlines on_each_cpu().  softirq.c was the most appropriate file I could
> >     find, but it doesn't seem to justify creating a new file.
> >  
> >     Oh, and fix up that comment over (under?) x86's smp_call_function().  It
> >     drives me nuts.
> > 
> > Applying the patch in reverse against 2.6.17 (it doesn't apply cleanly, but
> > I've done what seems to be the moral equivalent) makes the suspend work
> > again.
> > 
> > Any ideas? It does not work with the latest git checkout as of today.
> 
> I guess the patch may interfere with the CPU hotplug badly.

Why do you think it would do that?

>  Could you please
> check if you can take CPU1 offline/online?

If something really wants "disable irqs on the other CPUs but not on this
CPU" semantics then it would need to use smp_call_function and a direct
call.  But it would be a strange thing to want to do, surely?
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