From: Lars-Peter Clausen <lars@metafoo.de>
To: "Lothar Waßmann" <LW@KARO-electronics.de>
Cc: linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [BUG] genirq: Race condition in ONESHOT IRQ handler disabling IRQ forever
Date: Mon, 06 Feb 2012 11:42:27 +0100 [thread overview]
Message-ID: <4F2FAE93.5020205@metafoo.de> (raw)
In-Reply-To: <20271.35831.227679.177366@ipc1.ka-ro>
On 02/06/2012 09:14 AM, =?utf-8?Q?Lothar_Wa=C3=9Fmann?= wrote:
> Hi,
>
> I already sent this to <linux-kernel@vger.kernel.org> on Feb. 1, 2012
> but did not get any response there. So resending to a wider audience
> with improved subject line:
>
> there is a race condition in the threaded IRQ handler code for oneshot
> interrupts that may lead to disabling an IRQ indefinitely. IRQs are
> masked before calling the hard-irq handler and are unmasked only after
> the soft-irq handler has been run. Thus if the hard-irq handler
> returns IRQ_HANDLED instead of IRQ_WAKE_THREAD, meaning the soft-irq
> will not be called, the interrupt will remain masked forever.
>
> This can happen due to a short pulse on the interrupt line, that
> triggers the interrupt logic, but goes undetected by the hard-irq
> handler. The problem can be reproduced with the TSC2007 touch
> controller driver that uses ONESHOT interrupts.
>
> The problem arises also with interrupt controllers that latch a level
> triggered IRQ until it is acknowledged (like the i.MX28 does).
> In this case the IRQ status bit will remain asserted after the
> soft-irq finishes and retrigger the interrupt while the interrupt line
> is already deasserted.
>
> The following patch would solve the problem, but I'm not sure whether
> it's the Right Thing(TM) to do. Especially wrt. shared interrupts.
>
> diff --git a/kernel/irq/handle.c b/kernel/irq/handle.c
> index 470d08c..93beadb 100644
> --- a/kernel/irq/handle.c
> +++ b/kernel/irq/handle.c
> @@ -146,6 +146,11 @@ handle_irq_event_percpu(struct irq_desc *desc, struct irqaction *action)
> /* Fall through to add to randomness */
> case IRQ_HANDLED:
> random |= action->flags;
> + /* unmask the IRQ that has been left masked
> + * due to race condition
> + */
> + if (res == IRQ_HANDLED && (action->flags & IRQF_ONESHOT))
> + unmask_irq(desc);
> break;
>
> default:
I think a better fix is to check the return value of handle_irq_event in
handle_level_irq and if the IRQ_WAKE_THREADED bit is not set unmask the irq.
The same should probably also be done for handle_fasteoi_irq.
next prev parent reply other threads:[~2012-02-06 10:41 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-02-06 8:14 [BUG] genirq: Race condition in ONESHOT IRQ handler disabling IRQ forever =?utf-8?Q?Lothar_Wa=C3=9Fmann?=
2012-02-06 10:42 ` Lars-Peter Clausen [this message]
2012-02-07 9:03 ` Yong Zhang
2012-02-07 10:01 ` Lothar Waßmann
2012-02-07 12:34 ` Yong Zhang
2012-02-07 12:52 ` Lothar Waßmann
2012-02-07 13:07 ` Lars-Peter Clausen
2012-02-07 13:38 ` [PATCH] genirq: Fix race condition in ONESHOT irq handler Lothar Waßmann
2012-02-07 17:03 ` Thomas Gleixner
2012-02-08 6:05 ` Lothar Waßmann
2012-02-08 10:38 ` Thomas Gleixner
2012-02-09 8:40 ` Lothar Waßmann
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=4F2FAE93.5020205@metafoo.de \
--to=lars@metafoo.de \
--cc=LW@KARO-electronics.de \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-kernel@vger.kernel.org \
--cc=tglx@linutronix.de \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).