Re: IDE issues with "choose_drive"

[Benjamin Herrenschmidt <benh@kernel.crashing.org>]

On Thu, 2005-10-06 at 11:02 +1000, Benjamin Herrenschmidt wrote:
> > The first one is the one I'm trying to fix, it's basically a hang on
> > wakeup from sleep. What happens is that both drives are blocked
> > (suspended, drive->blocked is set). Their IO queues contains some
> > requests that haven't been serviced yet. We receive the resume()
> > callback for one of them. We react by inserting a wakeup request at the
> > head of the queue and waiting for it to complete. However, when we reach
> > ide_do_request(), choose_drive() may return the other drive (the one
> > that is still sleeping). In this case, we hit the test for blocked queue
> > and just break out of the loop. We end up never servicing the other
> > drive queue which is the one we are trying to wakeup, thus we hang.
> 
> Oh, and here's the ugly workaround beeing tested by the users who are
> having the problem so far. Not really a proper fix though...

No reply ... it's a bit urgent as it may bite any system trying to
suspend with a slave IDE disk at least (not including the other possible
problems I've spotted  with this code).

I'm tempted to just send my workaround patch to Linus & Andrew (might
still make it into 2.6.14). That would at least fix the bug with resume
from sleep. What do you think ?

Ben.


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