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SubjectRe: [ 57/72] genirq: Unmask oneshot irqs when thread was not woken
Date
On 2012-02-28 02:05 +0100, Greg KH wrote:

> 3.2-stable review patch. If anyone has any objections, please let me know.

Alas, the commit below broke the WiFi on my laptop, where
"iwlist wlan0 scan" now just reports: " wlan0 No scan results".

This is not specific to 3.2, the same problem exists in 3.0.23 and
3.3-rc6 while previous releases worked.

The laptop is an Acer TravelMate 2490 with a Broadcom chip:

,----
| 06:02.0 Network controller: Broadcom Corporation BCM4318 [AirForce One 54g] 802.11g Wireless LAN Controller (rev 02)
| Subsystem: AMBIT Microsystem Corp. TravelMate 2410
| Flags: bus master, fast devsel, latency 64, IRQ 10
| Memory at d0002000 (32-bit, non-prefetchable) [size=8K]
| Kernel driver in use: b43-pci-bridge
`----

I'll be happy to give more information when needed.

Cheers,
Sven


> From: Thomas Gleixner <tglx@linutronix.de>
>
> commit ac5637611150281f398bb7a47e3fcb69a09e7803 upstream.
>
> When the primary handler of an interrupt which is marked IRQ_ONESHOT
> returns IRQ_HANDLED or IRQ_NONE, then the interrupt thread is not
> woken and the unmask logic of the interrupt line is never
> invoked. This keeps the interrupt masked forever.
>
> This was not noticed as most IRQ_ONESHOT users wake the thread
> unconditionally (usually because they cannot access the underlying
> device from hard interrupt context). Though this behaviour was nowhere
> documented and not necessarily intentional. Some drivers can avoid the
> thread wakeup in certain cases and run into the situation where the
> interrupt line s kept masked.
>
> Handle it gracefully.
>
> Reported-and-tested-by: Lothar Wassmann <lw@karo-electronics.de>
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
>
> ---
> kernel/irq/chip.c | 25 +++++++++++++++++++++++--
> 1 file changed, 23 insertions(+), 2 deletions(-)
>
> --- a/kernel/irq/chip.c
> +++ b/kernel/irq/chip.c
> @@ -330,6 +330,24 @@ out_unlock:
> }
> EXPORT_SYMBOL_GPL(handle_simple_irq);
>
> +/*
> + * Called unconditionally from handle_level_irq() and only for oneshot
> + * interrupts from handle_fasteoi_irq()
> + */
> +static void cond_unmask_irq(struct irq_desc *desc)
> +{
> + /*
> + * We need to unmask in the following cases:
> + * - Standard level irq (IRQF_ONESHOT is not set)
> + * - Oneshot irq which did not wake the thread (caused by a
> + * spurious interrupt or a primary handler handling it
> + * completely).
> + */
> + if (!irqd_irq_disabled(&desc->irq_data) &&
> + irqd_irq_masked(&desc->irq_data) && !desc->threads_oneshot)
> + unmask_irq(desc);
> +}
> +
> /**
> * handle_level_irq - Level type irq handler
> * @irq: the interrupt number
> @@ -362,8 +380,8 @@ handle_level_irq(unsigned int irq, struc
>
> handle_irq_event(desc);
>
> - if (!irqd_irq_disabled(&desc->irq_data) && !(desc->istate & IRQS_ONESHOT))
> - unmask_irq(desc);
> + cond_unmask_irq(desc);
> +
> out_unlock:
> raw_spin_unlock(&desc->lock);
> }
> @@ -417,6 +435,9 @@ handle_fasteoi_irq(unsigned int irq, str
> preflow_handler(desc);
> handle_irq_event(desc);
>
> + if (desc->istate & IRQS_ONESHOT)
> + cond_unmask_irq(desc);
> +
> out_eoi:
> desc->irq_data.chip->irq_eoi(&desc->irq_data);
> out_unlock:


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