linux-kernel - Re: [PATCH] ioapic: fix potential resume deadlock

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Message-Id: <1305565471.26846.4.camel@sbsiddha-MOBL3.sc.intel.com>
Date:	Mon, 16 May 2011 10:04:31 -0700
From:	Suresh Siddha <suresh.b.siddha@...el.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Daniel J Blueman <daniel.blueman@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, H Peter Anvin <hpa@...or.com>,
	"x86@...nel.org" <x86@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ioapic: fix potential resume deadlock

On Mon, 2011-05-16 at 04:32 -0700, Ingo Molnar wrote: 
> * Daniel J Blueman <daniel.blueman@...il.com> wrote:
> 
> > Hi Suresh,
> > 
> > On 14 May 2011 01:48, Suresh Siddha <suresh.b.siddha@...el.com> wrote:
> > > On Wed, 2011-05-11 at 09:15 -0700, Daniel J Blueman wrote:
> > >> Superb, this works, tested against 2.6.39-rc7 and addresses the "BUG:
> > >> sleeping function called from invalid context at mm/slub.c:824"
> > >> warning I was previously seeing. It would be good to get this fix into
> > >> 2.6.39-final if possible.
> > >>
> > >> Tested-by: Daniel J Blueman <daniel.blueman@...il.com>
> > >
> > > Thanks Daniel for testing my quick patch. I have appended the complete
> > > patch which cleans up this code.
> > >
> > > Ingo, This patch is relatively big (mostly removes the duplicate code
> > > and changes the location where we allocate ioapic_saved_data, so that
> > > this can be shared between interrupt-remapping and io-apic
> > > suspend/resume flows). May be this can go into 2.6.40-rc1 and probably
> > > go to 2.6.39-stable?
> > >
> > > Or we can take the Daniel's GFP_ATOMIC patch for 2.6.39 and push this
> > > patch for 2.6.40-rc1. I am ok either way.
> > []
> > 
> > Testing this, all looks well in that the patch resolves the
> > potentially sleeping allocation, however I do see (on boot) this
> > suspicious message (though suspend and resume does work):
> > 
> > IOAPIC 0: suspend/resume impossible!
> > 
> > I guess it's not expected...

oops. I had a spurious initialization, from the earlier attempts to fix
this that was still left out.

> No. Has this been introduced by Suresh's patch?

Ofcourse yes ;(

Will fix this and split the patch into multiple steps.

thanks,
suresh

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