On Thu, Feb 26, 2009 at 3:10 PM, Rafael J. Wysocki <rjw@xxxxxxx> wrote:
> On Thursday 26 February 2009, Arve Hjønnevåg wrote:
>> On Thu, Feb 26, 2009 at 2:10 PM, Linus Torvalds
>> <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote:
>> >
>> >
>> > On Thu, 26 Feb 2009, Rafael J. Wysocki wrote:
>> >>
>> >> Well, how exactly the $subject patch does cause this problem to happen?
>> >
>> > Rafael, the problem is that if an interrupt happens while it's disabled -
>> > but before the CPU has actually turned all interrupts off - the CPU will
>> > ACK the interrupt (but just set a flag for it being PENDING), so now the
>> > chipset logic around it will not see it as pending any more, so now the
>> > chipset won't auto-wake the CPU immediately (or more likely, it won't
>> > even suspend it).
>> >
>> > It's trivial to fix multiple ways, so I wouldn't worry. The most trivial
>> > way is to just have some sysdev drievr code simply do something like
>> >
>> > static int sysdev_suspend()
>> > {
>> > for_each_irq(irq,desc) {
>> > if (!(desc->flags & IRQF_WAKE))
>> > continue;
>> > if (desc->flags & IRQ_PENDING)
>> > return -EBUSY;
>> > }
>> > return 0;
>> > }
>> >
>> > and that should automatically mean that if any irq is pending, the suspend
>> > will fail and we'll immediately wake up again.
>> >
>> > It looks trivial, and I don't understand why Arve can't just do the sysdev
>> > thing.
>>
>> I can. My point is that the patch breaks our existing code.
>
> Is that a mainline kernel code?
No, the msm suspend support has not been merged.
>
>> If anyone else uses edge triggered wakeup interrupt it may break from them as
>> well. The main question if this should be fixed separately for every
>> platform that needs it, or if pending wakeup interrupts should always
>> abort sleep.
>
> Well, I'm not really sure if this is the problem. In fact the problem is that
> you have a regular device the interrupt of which can be a wake-up one. I think
Is that not a common case and what enable_irq_wake is for?
> the problem wouldn't have existed at all if it had been a sysdev. Is that
> correct?
How many sysdevs use interrupts?
I found may drivers in the mainline kernel that use enable_irq_wake,
but I did not see any that handle this race condition.
--
Arve Hjønnevåg
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