linux-kernel - Re: 2.6.30: hibernation/swsusp lockup due to acpi-cpufreq

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Date:	Tue, 16 Jun 2009 14:09:23 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Johannes Stezenbach <js@...21.net>
Cc:	venkatesh.pallipadi@...el.com, rjw@...k.pl,
	linux-kernel@...r.kernel.org, davej@...hat.com, pavel@....cz,
	linux-acpi@...r.kernel.org, lenb@...nel.org, arjan@...radead.org,
	tglx@...utronix.de
Subject: Re: 2.6.30: hibernation/swsusp lockup due to acpi-cpufreq

On Tue, 16 Jun 2009 22:40:39 +0200
Johannes Stezenbach <js@...21.net> wrote:

> On Tue, Jun 16, 2009 at 01:25:58PM -0700, Pallipadi, Venkatesh wrote:
> >
> > Can you try the patch below (your changes + a warnon). That should give
> > the stack trace with successful suspend-resume.
> >
> > acpi-cpufreq will not directly disable interrupt and call these routines.
> > So, it will be interesting to see how we are ending up in this state.
>
> Yes, I actually had the same idea and just did it ;-)
> I also found this:
> http://lkml.org/lkml/2007/7/17/674
>
> ------------[ cut here ]------------
> WARNING: at kernel/up.c:18 smp_call_function_single+0x45/0x60()
> Hardware name: 2373Y4M
> Modules linked in: ath5k mac80211 cfg80211 uhci_hcd ehci_hcd
> Pid: 4139, comm: bash Not tainted 2.6.30 #8
> Call Trace:
>  [<c011ea0d>] warn_slowpath_common+0x60/0x90
>  [<c010d86c>] ? do_drv_read+0x0/0x31
>  [<c011ea4a>] warn_slowpath_null+0xd/0x10
>  [<c013acc1>] smp_call_function_single+0x45/0x60
>  [<c010d4e5>] get_cur_val+0x62/0x6c
>  [<c010d72f>] get_cur_freq_on_cpu+0x35/0x58
>  [<c03786e9>] cpufreq_suspend+0x76/0xd9
>  [<c0136c3b>] ? clockevents_notify+0x1e/0x68
>  [<c02ff570>] sysdev_suspend+0x4e/0x182
>  [<c013fd28>] hibernation_snapshot+0x89/0x16b
>  [<c013fe99>] hibernate+0x8f/0x147
>  [<c013ec82>] ? state_store+0x0/0xa2
>  [<c013ecd7>] state_store+0x55/0xa2
>  [<c013ec82>] ? state_store+0x0/0xa2
>  [<c024dff5>] kobj_attr_store+0x1a/0x22
>  [<c01a7164>] sysfs_write_file+0xb4/0xdf
>  [<c01a70b0>] ? sysfs_write_file+0x0/0xdf
>  [<c0170cf2>] vfs_write+0x8a/0x12c
>  [<c0170e2d>] sys_write+0x3b/0x60
>  [<c01028f4>] sysenter_do_call+0x12/0x26
> ---[ end trace 1c2172bce3982a59 ]---

Right, so it's the suspend-must-disable-local-interrupts thing.  Again.
 create_image()'s local_irq_disable().

It was wrong to call work_on_cpu() with lcoal interrupts disabled, and
it's now wrong to call smp_call_function_single() with local interrupts
disabled.  It's just that smp_call_function_single() warns while
work_on_cpu() didn't.

That all explains the warning But afaik we still don't know why your
machine actually failed.  Perhaps it is a side-efect of emitting the
warning when the console is in a weird state?

So..  what to do?  Possibly we could hack cpufreq to not use
smp_call_function_single() if the call is to be done on the local CPU. 
But SMP might still be broken - if it really does want to do a cross-cpu
call.

Why does cpufreq need to do a cross-CPU get_cur_freq_on_cpu() call at
suspend time _anyway_?  Surely cpufreq knows the target CPU's frequency
from its internal in-main-memory state?
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