Re: Threaded interrupts for synaptic touchscreen in HTC dream
From: David Brownell
Date: Wed Jul 22 2009 - 12:52:02 EST
On Wednesday 22 July 2009, Thomas Gleixner wrote:
> main interrupt
> hardirq handler wakes main thread handler
>
> main thread handler
> bus magic
> subdevice1 "hardirq" handler wakes subdevice1 irq thread
> subdevice2 "hardirq" handler wakes subdevice2 irq thread
Why force this wasteful/undesired "all subdevices must
have their own IRQ handling thread" policy?
As previously noted, a single thread typically suffices.
There's no need to waste a dozen (or so) pages of memory
for such purposes ... these events are (as noted most
recently by Mark) infrequent/rare and performance isn't
a functionality gatekeeper. Plus ...
> main thread handler waits for subdevice1/2 handlers to complete
... sharing that thread can eliminate that synchronization
problem, and simplify the whole process.
> subdevice1 thread handler
> bus magic
> ....
> thread_fn returns
> signal main thread handler via completion
>
> subdevice2 thread handler
> bus magic
> ....
> thread_fn returns
> signal main thread handler via completion
>
> main thread handler resumes
> bus magic
> main thread handler returns from thread_fn
> unmask main interrupt
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/