Date: Mon, 14 Jun 2010 15:33:54 +0200 (CEST)
From: Thomas Gleixner <tglx@linutronix.de>
To: "Darcy L. Watkins" <dwatkins@tranzeo.com>
cc: will_schmidt@vnet.ibm.com, LKML <linux-kernel@vger.kernel.org>,
       rt-users <linux-rt-users@vger.kernel.org>,
       John Stultz <johnstul@us.ibm.com>, Nick Piggin <npiggin@suse.de>
Subject: Re: [ANNOUNCE] 2.6.33.5-rt23
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On Thu, 10 Jun 2010, Darcy L. Watkins wrote:
> 
> 
> On Thu, 2010-06-10 at 08:56 -0700, Will Schmidt wrote:
> > On Thu, 2010-06-10 at 08:07 +0200, Thomas Gleixner wrote:
> > > On Wed, 9 Jun 2010, Will Schmidt wrote:
> > >
> > > > On Wed, 2010-06-09 at 18:44 +0200, Thomas Gleixner wrote:
> > > > I'm still on 2.6.33.5-rt22 on powerpc, and have run into a couple
> > > > "sleeping function called from invalid context..." BUGs.   The
> > first was
> > > > during system boot, second during a 'make'.
> > > >
> > > > relevant code paths don't seem to have changed between -rt22 and
> > -rt23,
> > > > so I think still valid.. :-) 
> > > >
> > > > This is on a POWER7 system, which may have opened up some timing
> > > > windows, wrt previous runs on POWER6 systems.
> > > >
> > > >
> > > > BUG: sleeping function called from invalid context at
> > > > kernel/rtmutex.c:684
> > >
> > > > [c000000078cf2cf0] [c000000000131a04] .irq_to_desc_alloc_node
> > +0xdc/0x2b8
> > >
> > > Grr. I thought I had the SPARSE_IRQ stuff disabled on -rt, but seems
> > > it came back somehow. Can you disable that, or does you machine
> > depend
> > > on it ?
> > 
> > I'm not sure whether it is required by the architecture.  I do see
> > that
> > SPARSE_IRQ is disabled in arch/x86/Kconfig with a !PREEMPT_RT, but I
> > don't see an equivalent 'disable' in arch/powerpc/Kconfig. 
> > 
>
> I see it as "y" in my .config for a powerpc 405 build.  This appears to
> run on my system (although I haven't loaded up the rt23 build on the
> target yet - last one loaded up was rt22).
> 
> What should I expect to see different if SPARSE_IRQ is turned off?

The difference is that you can trigger "scheduling while atomic". The
warning Will has seen depends on debug options.

Thanks,

	tglx
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