linux-kernel - Re: [ 57/72] genirq: Unmask oneshot irqs when thread was not woken

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Date:	Tue, 06 Mar 2012 22:07:30 +0100
From:	Sven Joachim <svenjoac@....de>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Stefan Lippers-Hollmann <s.L-H@....de>,
	Greg KH <gregkh@...uxfoundation.org>,
	LKML <linux-kernel@...r.kernel.org>, stable@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Jonathan Nieder <jrnieder@...il.com>,
	linux-wireless@...r.kernel.org,
	Stefano Brivio <stefano.brivio@...imi.it>
Subject: Re: [ 57/72] genirq: Unmask oneshot irqs when thread was not woken

Am 06.03.2012 um 21:26 schrieb Thomas Gleixner:

> On Tue, 6 Mar 2012, Sven Joachim wrote:
>> Am 06.03.2012 um 20:31 schrieb Thomas Gleixner:
>> 
>> > Stephan, Sven: Can you please provide the output of /proc/interrupts ?
>> 
>> Here is mine, from a freshly booted 3.3-rc6 kernel.
>> 
>> Cheers,
>>        Sven
>> 
>>            CPU0       
>>   0:      25050    XT-PIC-XT-PIC    timer
>>   1:        101    XT-PIC-XT-PIC    i8042
>>   2:          0    XT-PIC-XT-PIC    cascade
>>   3:          1    XT-PIC-XT-PIC  
>>   4:          1    XT-PIC-XT-PIC  
>>   5:          0    XT-PIC-XT-PIC    ehci_hcd:usb1, uhci_hcd:usb2
>>   6:          1    XT-PIC-XT-PIC    i915, uhci_hcd:usb5, yenta
>>   7:          1    XT-PIC-XT-PIC  
>>   8:          0    XT-PIC-XT-PIC    rtc0
>>   9:        634    XT-PIC-XT-PIC    acpi
>>  10:        341    XT-PIC-XT-PIC    uhci_hcd:usb4, snd_hda_intel, b43
>
> Ah, XT-PIC uses handle_level_irq(). /me bangs head against desk.
>
> Does the patch below fix the problem for you ?

Yep, it does.  Thanks!

> ----------------->
> Subject: genirq: Clear action->thread_mask if IRQ_ONESHOT is not set
>
> commit ac5637611(genirq: Unmask oneshot irqs when thread was not
> woken) fails to unmask when a !IRQ_ONESHOT threaded handler is handled
> by handle_level_irq. This happens because thread_mask is or'ed
> unconditionally in irq_wake_thread(), but for !IRQ_ONESHOT interrupts
> never cleared. So the check for !desc->thread_active fails and keeps
> the interrupt disabled.
>
> Keep the thread_mask zero for !IRQ_ONESHOT interrupts.
>
> Reported-by: Sven Joachim <svenjoac@....de>
> Cc: stable@...r.kernel.org
> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
> ---
>
> Index: linux-2.6/kernel/irq/manage.c
> ===================================================================
> --- linux-2.6.orig/kernel/irq/manage.c
> +++ linux-2.6/kernel/irq/manage.c
> @@ -996,11 +996,13 @@ __setup_irq(unsigned int irq, struct irq
>  	 * Setup the thread mask for this irqaction. Unlikely to have
>  	 * 32 resp 64 irqs sharing one line, but who knows.
>  	 */
> -	if (new->flags & IRQF_ONESHOT && thread_mask == ~0UL) {
> -		ret = -EBUSY;
> -		goto out_mask;
> +	if (new->flags & IRQF_ONESHOT) {
> +		if (thread_mask == ~0UL) {
> +			ret = -EBUSY;
> +			goto out_mask;
> +		}
> +		new->thread_mask = new->flags & IRQF_ONESHOT;
>  	}
> -	new->thread_mask = 1 << ffz(thread_mask);
>  
>  	if (!shared) {
>  		init_waitqueue_head(&desc->wait_for_threads);
--
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