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Date: Fri, 10 Apr 2009 16:01:37 -0700
From: Andrew Morton <akpm@...ux-foundation.org>
To: Alessio Igor Bogani <abogani@...ware.it>
Cc: oakad@...oo.com, linux-kernel@...r.kernel.org, abogani@...ware.it,
Ingo Molnar <mingo@...e.hu>,
Thomas Gleixner <tglx@...utronix.de>,
Alan Cox <alan@...rguk.ukuu.org.uk>
Subject: Re: [PATCH] tifm: avoid inconsistent lock state
On Thu, 9 Apr 2009 16:52:03 +0200
Alessio Igor Bogani <abogani@...ware.it> 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@...ware.it>
> ---
> 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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