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Date: Tue, 30 May 2006 21:14:42 -0700
From: Andrew Morton <akpm@osdl.org>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: linux-kernel@vger.kernel.org, mingo@elte.hu
Subject: Re: 2.6.17-rc5-mm1
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On Tue, 30 May 2006 23:17:28 -0400
Steven Rostedt <rostedt@goodmis.org> wrote:

> Oh look what I found.  It seems that little driver of Andrew's has come
> back to haunt me :)  And I think it has to do with that cute little
> disable_irq in vortex_timer again.
> 
> 
> ============================
> [ BUG: illegal lock usage! ]
> ----------------------------
> illegal {in-hardirq-W} -> {hardirq-on-W} usage.
> idle/0 [HC0[0]:SC1[2]:HE1:SE0] takes:
>  (&vp->lock){++..}, at: [<f8895b44>] vortex_timer+0x414/0x490 [3c59x]
> {in-hardirq-W} state was registered at:
>   [<c013c759>] lockdep_acquire+0x59/0x70
>   [<c031a11d>] _spin_lock+0x3d/0x50
>   [<f8898983>] boomerang_interrupt+0x33/0x470 [3c59x]
>   [<c0147a11>] handle_IRQ_event+0x31/0x70
>   [<c0149304>] handle_level_irq+0xa4/0x100
>   [<c0105658>] do_IRQ+0x58/0x90
>   [<c010348d>] common_interrupt+0x25/0x2c
>   [<c010162d>] cpu_idle+0x4d/0xb0
>   [<c01002e5>] rest_init+0x45/0x50
>   [<c03f881a>] start_kernel+0x32a/0x460
>   [<c0100210>] 0xc0100210
> irq event stamp: 220672
> hardirqs last  enabled at (220672): [<c031aa45>] _spin_unlock_irqrestore+0x65/00hardirqs last disabled at (220671): [<c031a5d6>] _spin_lock_irqsave+0x16/0x60
> softirqs last  enabled at (220658): [<c0124453>] __do_softirq+0xf3/0x110
> softirqs last disabled at (220667): [<c01244e5>] do_softirq+0x75/0x80
> 
> other info that might help us debug this:
> no locks held by idle/0.
> 
> stack backtrace:
>  <c01052bb> show_trace+0x1b/0x20  <c01052e6> dump_stack+0x26/0x30
>  <c013af5d> print_usage_bug+0x22d/0x240  <c013b591> mark_lock+0x621/0x6c0
>  <c013b6ff> __lockdep_acquire+0xcf/0xd30  <c013c759> lockdep_acquire+0x59/0x70
>  <c031a172> _spin_lock_bh+0x42/0x50  <f8895b44> vortex_timer+0x414/0x490 [3c59x] <c0128cf9> run_timer_softirq+0xc9/0x1a0  <c01243e7> __do_softirq+0x87/0x110
>  <c01244e5> do_softirq+0x75/0x80  <c0124650> irq_exit+0x50/0x60
>  <c01102a3> smp_apic_timer_interrupt+0x73/0x80  <c010354e> apic_timer_interrupt0 <c010162d> cpu_idle+0x4d/0xb0  <c010f2a5> start_secondary+0x455/0x500
>  <00000000> 0x0  <f7f85fb4> 0xf7f85fb4

Without having looked at it very hard, I'd venture that this is a false
positive - that driver uses disable_irq() to prevent reentry onto that
lock.

It does that because it knows it's about to spend a long time talking with
the mii registers and it doesn't want to do that with interrupts disabled.

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