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Subject: Re: 2.6.33.5 rt23: sleeping function called from invalid context
From: john stultz <johnstul@us.ibm.com>
To: Fernando Lopez-Lezcano <nando@ccrma.Stanford.EDU>
Cc: Thomas Gleixner <tglx@linutronix.de>, LKML <linux-kernel@vger.kernel.org>,
       rt-users <linux-rt-users@vger.kernel.org>,
       Steven Rostedt <rostedt@goodmis.org>, Nick Piggin <npiggin@suse.de>
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Date: Thu, 08 Jul 2010 18:44:32 -0700
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On Thu, 2010-07-08 at 10:37 -0700, john stultz wrote:
> On Wed, 2010-07-07 at 20:54 -0700, Fernando Lopez-Lezcano wrote:
> > After a suspend/wake up cycle, just after upgrading to fc12 (I did not
> > see this with the same basic kernel - that is, compiled from the same
> > source + patches - under fc11). 
> > 
> > BUG: sleeping function called from invalid context at
> > kernel/rtmutex.c:684
> > pcnt: 0 0 in_atomic(): 0, irqs_disabled(): 1, pid: 10582, name:
> > pm-suspend
> > Pid: 10582, comm: pm-suspend Not tainted
> > 2.6.33.5-120.rt23.1.fc11.ccrma.i686.rtPAE #1
> > Call Trace:
> > [<c042eced>] __might_sleep+0xcc/0xd4
> > [<c0464f57>] rt_spin_lock_fastlock.clone.1+0x26/0x5f
> > [<c0792862>] rt_spin_lock+0x8/0xa
> > [<c040dddc>] read_persistent_clock+0x11/0x30
> > [<c045d1de>] timekeeping_suspend+0xe/0x4e
> > [<c0640c9e>] sysdev_suspend+0x15c/0x356
> > [<c0792906>] ? _mutex_unlock+0x8/0xa
> > [<c046afc1>] suspend_devices_and_enter+0xea/0x17f
> 
> Huh. Looks like the lock protecting the RTC/CMOS might need to be
> converted to a raw spinlock, since suspend/resume is probably done with
> irqs off.

Oof. The rtc_lock is used all over the place. Not sure if we really want
to convert it to a raw_spinlock. 

However, sysdev_suspend() wants interrupts off on all the .suspend
calls. I'm surprised we haven't hit this issue with more drivers. Maybe
no one is testing suspend w/ -rt? Or am I just missing an obvious
solution?

Thomas, any thoughts on this? 

thanks
-john



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