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Date: Fri, 14 Mar 2008 00:07:31 -0400
From: Len Brown <lenb@...nel.org>
To: Venki Pallipadi <venkatesh.pallipadi@...el.com>
Cc: "Rafael J. Wysocki" <rjw@...k.pl>,
Miklos Szeredi <miklos@...redi.hu>, linux-acpi@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: ACPI lockdep warning on boot, 2.6.25-rc5
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@...el.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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