On Mon, 10 Jul 2006, Brown, Len wrote:
> >... a similar fix needs to be made in
> drivers/acpi/osl.c:acpi_os_wait_semaphore().
> >If interrupts are disabled the timeout argument should be set to 0, so
> that the
> >routine will call down_trylock() instead of down() or
> schedule_timeout_interruptible().
>
> We used to have a hack in acpi_os_wait_semaphore():
>
> if (in_atomic())
> timeout = 0;
>
> But we deleted it upon ACPICA 20060608 when the
> ACPICA locks that were used at interrupt-time were
> converted to be Linux spin-locks.
>
> Now it is still conceivable that during resume before interrutps are
> re-enabled,
> the PCI interrupt link devices run AML and go to acquire an AML mutex
> with
> a timeout. However, we are single threaded at that point, so it isn't
> possible for them to acquire the mutex -- timeout or not.
>
> I don't like the looks of the "workaround" above -- it makes the code
> confusing.
>
> I'd be open to putting a BUG_ON() in the sleep case if interrupts are
> not enabled.
>
> Is there another case that you can think of?
I can't give you an answer now; this case was triggered during
resume-from-disk on my computer at home.
Tonight I'll attach a stack trace to the bug report. Let's continue
further discussion there, off-list.
Alan Stern
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