Re: [PATCH] tifm: avoid inconsistent lock state

[Andrew Morton]

On Thu,  9 Apr 2009 16:52:03 +0200
Alessio Igor Bogani <abogani@xxxxxxxxxx> wrote:

> Avoid the following INFO from lock debugging:
> 
> [  901.190400] irq 18: nobody cared (try booting with the "irqpoll" option)
> [  901.190411] Pid: 4255, comm: pulseaudio Not tainted 2.6.30-rc1 #21
> [  901.190415] Call Trace:
> [  901.190419]  <IRQ>  [<ffffffffa0022969>] ? tifm_7xx1_isr+0x99/0x170 [tifm_7xx1]
> [  901.190452]  [<ffffffff802bbdcb>] __report_bad_irq+0x2b/0xb0
> [  901.190459]  [<ffffffff802bbfe8>] note_interrupt+0x198/0x1e0
> [  901.190467]  [<ffffffff802bc6ad>] handle_fasteoi_irq+0xdd/0x110
> [  901.190474]  [<ffffffff80215bd4>] handle_irq+0x24/0x40
> [  901.190483]  [<ffffffff8074d0a3>] do_IRQ+0x73/0x100
> [  901.190491]  [<ffffffff80213cd3>] ret_from_intr+0x0/0x16
> [  901.190495]  <EOI>  [<ffffffff80747eb2>] ? _spin_unlock_irqrestore+0x72/0x80
> [  901.190510]  [<ffffffff8027356e>] ? add_wait_queue+0x4e/0x60
> [  901.190517]  [<ffffffff803292d6>] ? __pollwait+0x86/0x110
> [  901.190535]  [<ffffffffa016c831>] ? snd_ctl_poll+0x61/0x70 [snd]
> [  901.190543]  [<ffffffff803295cc>] ? do_sys_poll+0x21c/0x4c0
> [  901.190549]  [<ffffffff80329250>] ? __pollwait+0x0/0x110
> [  901.190556]  [<ffffffff80329360>] ? pollwake+0x0/0x50
> [  901.190562]  [<ffffffff80329360>] ? pollwake+0x0/0x50
> [  901.190569]  [<ffffffff80329360>] ? pollwake+0x0/0x50
> [  901.190575]  [<ffffffff80329360>] ? pollwake+0x0/0x50
> [  901.190581]  [<ffffffff80329360>] ? pollwake+0x0/0x50
> [  901.190587]  [<ffffffff80329360>] ? pollwake+0x0/0x50
> [  901.190594]  [<ffffffff80747e07>] ? _spin_unlock_irq+0x37/0x70
> [  901.190601]  [<ffffffff80747e11>] ? _spin_unlock_irq+0x41/0x70
> [  901.190609]  [<ffffffff8024c283>] ? finish_task_switch+0x83/0x140
> [  901.190616]  [<ffffffff8024c240>] ? finish_task_switch+0x40/0x140
> [  901.190625]  [<ffffffff80288558>] ? __lock_acquire+0x328/0x13e0
> [  901.190634]  [<ffffffff8047ac0e>] ? _raw_spin_unlock+0x7e/0xa0
> [  901.190642]  [<ffffffff8027cf51>] ? getnstimeofday+0x61/0xf0
> [  901.190649]  [<ffffffff80276e51>] ? ktime_get_ts+0x61/0x70
> [  901.190656]  [<ffffffff803289e8>] ? poll_select_set_timeout+0x88/0xa0
> [  901.190663]  [<ffffffff80329a7c>] ? sys_poll+0x7c/0x110
> [  901.190670]  [<ffffffff80213232>] ? system_call_fastpath+0x16/0x1b
> [  901.190675] handlers:
> [  901.190679] [<ffffffff8059f7d0>] (usb_hcd_irq+0x0/0xe0)
> [  901.190690] [<ffffffff8059f7d0>] (usb_hcd_irq+0x0/0xe0)
> [  901.190699] [<ffffffffa00228d0>] (tifm_7xx1_isr+0x0/0x170 [tifm_7xx1])
> [  901.190710] Disabling IRQ #18
> [  901.288126]
> [  901.288128] =================================
> [  901.288132] [ INFO: inconsistent lock state ]
> [  901.288135] 2.6.30-rc1 #21
> [  901.288137] ---------------------------------
> [  901.288140] inconsistent {IN-HARDIRQ-W} -> {HARDIRQ-ON-W} usage.
> [  901.288143] swapper/0 [HC0[0]:SC1[1]:HE1:SE0] takes:
> [  901.288145]  (&irq_desc_lock_class){?.-...}, at: [<ffffffff802bbbc3>] try_one_irq+0x33/0x160
> [  901.288156] {IN-HARDIRQ-W} state was registered at:
> [  901.288158]   [<ffffffffffffffff>] 0xffffffffffffffff
> [  901.288172] irq event stamp: 970106
> [  901.288174] hardirqs last  enabled at (970106): [<ffffffff80747e00>] _spin_unlock_irq+0x30/0x70
> [  901.288181] hardirqs last disabled at (970105): [<ffffffff807474cf>] _spin_lock_irq+0x1f/0x90
> [  901.288186] softirqs last  enabled at (970078): [<ffffffff8025f0e4>] __do_softirq+0x1d4/0x250
> [  901.288193] softirqs last disabled at (970103): [<ffffffff802144fc>] call_softirq+0x1c/0x30
> 
> Signed-off-by: Alessio Igor Bogani <abogani@xxxxxxxxxx>
> ---
>  drivers/misc/tifm_7xx1.c |    7 ++++---
>  1 files changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/misc/tifm_7xx1.c b/drivers/misc/tifm_7xx1.c
> index a6ef182..b38ee02 100644
> --- a/drivers/misc/tifm_7xx1.c
> +++ b/drivers/misc/tifm_7xx1.c
> @@ -41,11 +41,12 @@ static irqreturn_t tifm_7xx1_isr(int irq, void *dev_id)
>  	struct tifm_adapter *fm = dev_id;
>  	struct tifm_dev *sock;
>  	unsigned int irq_status, cnt;
> +	unsigned long flags;
>  
> -	spin_lock(&fm->lock);
> +	spin_lock_irqsave(&fm->lock, flags);
>  	irq_status = readl(fm->addr + FM_INTERRUPT_STATUS);
>  	if (irq_status == 0 || irq_status == (~0)) {
> -		spin_unlock(&fm->lock);
> +		spin_unlock_irqrestore(&fm->lock, flags);
>  		return IRQ_NONE;
>  	}
>  
> @@ -74,7 +75,7 @@ static irqreturn_t tifm_7xx1_isr(int irq, void *dev_id)
>  	else
>  		tifm_queue_work(&fm->media_switcher);
>  
> -	spin_unlock(&fm->lock);
> +	spin_unlock_irqrestore(&fm->lock, flags);
>  	return IRQ_HANDLED;
>  }
>  

Dunno, I think the problem here is in kernel/irq/spurious.c.

tifm_7xx1_isr() can legitimately use spin_lock() on that lock, because
it's running in hard IRQ context and "knows" that tifm_7xx1_isr()
cannot be reentered on this CPU while it is running.

But try_one_irq() is running tifm_7xx1_isr() with local interrupts
enabled, which upsets lockdep.

An appropriate fix might be to change try_one_irq() to run the handler
under local_irq_disable(), but I'm sure it'll get more complex than
that :(

But I suspect that the code as it stands is non-buggy.  Unless the
interrupt can magically come back to life.  In which case any change we
make is purely a make-lockdep-shut-up thing.

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