Re: [PATCH] pcf50633: use a dedicated workqueue for irq processing

[Andrew Morton <akpm@linux-foundation.org>]

On Tue, 28 Jul 2009 00:41:15 +0400
Paul Fertser <fercerpav@gmail.com> wrote:

> Using the default kernel "events" workqueue causes problems with
> synchronous adc readings if initiated from some task on the same
> workqueue.
> 
> I had a deadlock trying to use pcf50633_adc_sync_read from a
> power_supply class driver because the reading was initiated from the
> workqueue and it waited for the irq processing to complete (to get the
> result) and that was put on the same workqueue.

I don't get it.

Do you meant that pcf50633_adc_sync_read() was called via a
schedule_work() handler?  If so, wasn't that a bug?

The patch looks reasonable, but creating yet another kernel thread is a
bit sad.  And I suspect that other MFD drivers are doing the same thing
as pcf50633-core.c, in which case we should change those as well?

So..  please provide a more complete description of the problem which
is being solved so that we can explore alternative fixes.