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From: Len Brown <lenb@kernel.org>
Organization: Intel Open Source Technology Center
To: Venki Pallipadi <venkatesh.pallipadi@intel.com>
Subject: Re: ACPI lockdep warning on boot, 2.6.25-rc5
Date: Fri, 14 Mar 2008 00:07:31 -0400
User-Agent: KMail/1.9.9
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>, Miklos Szeredi <miklos@szeredi.hu>,
       linux-acpi@vger.kernel.org, linux-kernel@vger.kernel.org
References: <E1JZOGd-00057d-BU@pomaz-ex.szeredi.hu> <200803131614.33386.lenb@kernel.org> <20080314001819.GA32584@linux-os.sc.intel.com>
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applied to acpi-test

thanks,
-Len

On Thursday 13 March 2008, Venki Pallipadi wrote:
> On Thu, Mar 13, 2008 at 04:14:32PM -0400, Len Brown wrote:
> > On Wednesday 12 March 2008, Rafael J. Wysocki wrote:
> > > On Wednesday, 12 of March 2008, Miklos Szeredi wrote:
> > > > I don't know whether this is a problem in reality or not, but it does
> > > > interfere with debugging the rest of the kernel, since this turns off
> > > > lockdep at boottime.
> > > 
> > > Well, I think Venki should see it (CCed).
> > > 
> > > Thanks,
> > > Rafael
> > > 
> > >  
> > > > [    0.592488] ACPI: CPU0 (power states: C1[C1] C2[C2] C3[C3])
> > > > [    0.593038] ------------[ cut here ]------------
> > > > [    0.593267] WARNING: at kernel/lockdep.c:2035 trace_hardirqs_on+0xa0/0x115()
> > > > [    0.593596] Modules linked in:
> > > > [    0.593756] Pid: 0, comm: swapper Not tainted 2.6.25-rc5 #8
> > > > [    0.594017] 
> > > > [    0.594017] Call Trace:
> > > > [    0.594216]  [<ffffffff80231663>] warn_on_slowpath+0x58/0x6b
> > > > [    0.594495]  [<ffffffff80495966>] ? _spin_unlock_irqrestore+0x38/0x47
> > > > [    0.594809]  [<ffffffff80329a86>] ? acpi_os_release_lock+0x9/0xb
> > > > [    0.595103]  [<ffffffff80337840>] ? acpi_set_register+0x161/0x173
> > > > [    0.595401]  [<ffffffff8034c8d4>] ? acpi_processor_idle+0x1de/0x546
> > > > [    0.595706]  [<ffffffff8020a23b>] ? default_idle+0x0/0x73
> > > > [    0.595970]  [<ffffffff8024fc0e>] trace_hardirqs_on+0xa0/0x115
> > > > [    0.596049]  [<ffffffff8034c6f6>] ? acpi_processor_idle+0x0/0x546
> > > > [    0.596346]  [<ffffffff8034c8d4>] acpi_processor_idle+0x1de/0x546
> > > > [    0.596642]  [<ffffffff8020a23b>] ? default_idle+0x0/0x73
> > > > [    0.596912]  [<ffffffff8034c6f6>] ? acpi_processor_idle+0x0/0x546
> > > > [    0.597209]  [<ffffffff8020a23b>] ? default_idle+0x0/0x73
> > > > [    0.597472]  [<ffffffff8020a355>] cpu_idle+0xa7/0xd1
> > > > [    0.597717]  [<ffffffff80485fa1>] rest_init+0x55/0x57
> > > > [    0.597957]  [<ffffffff8062fb49>] start_kernel+0x29d/0x2a8
> > > > [    0.598215]  [<ffffffff8062f1da>] _sinittext+0x1da/0x1e1
> > > > [    0.598464] 
> > > > [    0.598546] ---[ end trace 778e504de7e3b1e3 ]---
> > 
> > Venki,
> > 
> > this reproduces in my t61 using Miklos' config (though i had to increase
> > the logbuff to catch it)
> > 
> > -Len
> 
> Below patch should fix this warning. I would say warning is pretty harmless.. 
> 
> Thanks,
> Venki
> 
> ---
> 
> This avoids the harmless WARNING by lockdep in acpi_processor_idle().
> 
> The reason for WARNING is because at the depth of idle handling code,
> some of the idle handlers disable interrupts, some times, while returning from
> the idle handler. After return, acpi_processor_idle and few other routines
> in the file did an unconditional local_irq_enable(). With LOCKDEP, enabling
> irq when it is alread enabled generates the below WARNING.
> 
> > > [    0.593038] ------------[ cut here ]------------
> > > [    0.593267] WARNING: at kernel/lockdep.c:2035 trace_hardirqs_on+0xa0/0x115()
> > > [    0.593596] Modules linked in:
> > > [    0.593756] Pid: 0, comm: swapper Not tainted 2.6.25-rc5 #8
> > > [    0.594017] 
> > > [    0.594017] Call Trace:
> > > [    0.594216]  [<ffffffff80231663>] warn_on_slowpath+0x58/0x6b
> > > [    0.594495]  [<ffffffff80495966>] ? _spin_unlock_irqrestore+0x38/0x47
> > > [    0.594809]  [<ffffffff80329a86>] ? acpi_os_release_lock+0x9/0xb
> > > [    0.595103]  [<ffffffff80337840>] ? acpi_set_register+0x161/0x173
> > > [    0.595401]  [<ffffffff8034c8d4>] ? acpi_processor_idle+0x1de/0x546
> > > [    0.595706]  [<ffffffff8020a23b>] ? default_idle+0x0/0x73
> > > [    0.595970]  [<ffffffff8024fc0e>] trace_hardirqs_on+0xa0/0x115
> > > [    0.596049]  [<ffffffff8034c6f6>] ? acpi_processor_idle+0x0/0x546
> > > [    0.596346]  [<ffffffff8034c8d4>] acpi_processor_idle+0x1de/0x546
> > > [    0.596642]  [<ffffffff8020a23b>] ? default_idle+0x0/0x73
> > > [    0.596912]  [<ffffffff8034c6f6>] ? acpi_processor_idle+0x0/0x546
> > > [    0.597209]  [<ffffffff8020a23b>] ? default_idle+0x0/0x73
> > > [    0.597472]  [<ffffffff8020a355>] cpu_idle+0xa7/0xd1
> > > [    0.597717]  [<ffffffff80485fa1>] rest_init+0x55/0x57
> > > [    0.597957]  [<ffffffff8062fb49>] start_kernel+0x29d/0x2a8
> > > [    0.598215]  [<ffffffff8062f1da>] _sinittext+0x1da/0x1e1
> > > [    0.598464] 
> > > [    0.598546] ---[ end trace 778e504de7e3b1e3 ]---
> 
> Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
> 
> Index: linux-2.6.git/drivers/acpi/processor_idle.c
> ===================================================================
> --- linux-2.6.git.orig/drivers/acpi/processor_idle.c	2008-03-12 05:17:12.000000000 -0700
> +++ linux-2.6.git/drivers/acpi/processor_idle.c	2008-03-13 10:00:47.000000000 -0700
> @@ -216,8 +216,10 @@
>  	 * test NEED_RESCHED:
>  	 */
>  	smp_mb();
> -	if (!need_resched())
> +	if (!need_resched()) {
>  		safe_halt();
> +		local_irq_disable();
> +	}
>  	current_thread_info()->status |= TS_POLLING;
>  }
>  
> @@ -421,7 +423,9 @@
>  		else
>  			acpi_safe_halt();
>  
> -		local_irq_enable();
> +		if (irqs_disabled())
> +			local_irq_enable();
> +
>  		return;
>  	}
>  
> @@ -530,7 +534,9 @@
>  		 *       skew otherwise.
>  		 */
>  		sleep_ticks = 0xFFFFFFFF;
> -		local_irq_enable();
> +		if (irqs_disabled())
> +			local_irq_enable();
> +
>  		break;
>  
>  	case ACPI_STATE_C2:
> --
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