Matthew Wilcox wrote:
> On Wed, Jun 04, 2008 at 08:57:16AM +0530, Balbir Singh wrote:
>> Saw this warning on an x86_64 box, while booting up 2.6.26-rc4. Has anybody else
>> seen it? Working on it?
>
> I've neither seen it, nor am I working on it, but I can decode it.
>
>> inconsistent {in-hardirq-W} -> {hardirq-on-W} usage.
>
> Translation: "This lock was previously grabbed in hardirq context. Now
> someone's taking it in process context without interrupts disabled.
> That could lead to a deadlock."
>
I understand this part. I did not want to interpret the data, but I think that's
a better way of reporting problems.
>> init/1 [HC0[0]:SC0[0]:HE1:SE1] takes:
>> (&fbc->lock){+...}, at: [<ffffffff80386382>] __percpu_counter_sum+0xf/0x5a
>
> That's the name of the lock -- &fbc->lock and the function where it
> happens.
>
>> {in-hardirq-W} state was registered at:
>> [<ffffffffffffffff>] 0xffffffffffffffff
>
> Drat, no backtrace for the guy who took the lock in hardirq context.
>
>> Call Trace:
>> [<ffffffff802518e6>] print_usage_bug+0x15e/0x16f
>> [<ffffffff8025281f>] mark_lock+0x22f/0x416
>> [<ffffffff80386382>] ? __percpu_counter_sum+0xf/0x5a
>> [<ffffffff80253576>] __lock_acquire+0x4e7/0xc8a
>> [<ffffffff80386382>] ? __percpu_counter_sum+0xf/0x5a
>> [<ffffffff80253da7>] lock_acquire+0x8e/0xb2
>> [<ffffffff80386382>] ? __percpu_counter_sum+0xf/0x5a
>> [<ffffffff805990d7>] _spin_lock+0x26/0x53
>> [<ffffffff80386382>] __percpu_counter_sum+0xf/0x5a
>> [<ffffffff803139e2>] ext3_statfs+0xd6/0x160
>
> ext3_statfs was the one who asked for the lock to be taken without
> disabling interrupts.
>
>
> Some percpu counters are supposed to be used from interrupt context.
> These are created with percpu_counter_init_irq. Others are not and
> should be created with percpu_counter_init. It seems like someone's
> made a mess of that rule. This is likely to be a driver, IMO. Perhaps
> you could work on tracking this down?
>
Sure, I will. Let me poke harder, I'll recheck all patches I have applied (if
any) on my current tree.
--
Warm Regards,
Balbir Singh
Linux Technology Center
IBM, ISTL
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