Re: [PATCH] ACPI: EC: do transaction from interrupt context

Alexey Starikovskiy
2008-09-27T05:37:54Z

Zhao Yakui wrote:
> Of course such laptops can still work well except that CPU
> interrupt will be disabled for some extra time after Alexey's patch is
> applied .(The some extra time depends on how many EC Inb/out operations
> are executed).
>
>
spinlock is released after each I/O, so by your own calculation
it is disabled for 1.5 usec.
You can then multiply this number by lifetime of the universe,
it does not mean anything.

Regards,
Alex.
> In my email the purpose that I point out 2000 EC I/O read/write
> operation doesn't indicate that 2000 EC I/O read/write will be executed
> per second. What I want to say is that EC I/O read/write is slow
> operation. If quite a lot of EC I/O read/write are accessed for some
> reasons in some time, the CPU interrupt will be disabled for a long
> time. In such case the normal laptop will be affected by this. (Of
> course maybe the affect will be very tiny).
> In fact in kernel source code if the race can be resolved by other
> synchronization protection mechanism, the spin_lock had better be
> avoided.
>
Please explain, I'd like to make poster of it :)