Re: [PATCH] 2.5.15 IDE 62

Martin Dalecki
2002-05-13T14:05:46Z

Uz.ytkownik Jens Axboe napisa?:
> On Mon, May 13 2002, Martin Dalecki wrote:
>
>>Mon May 13 12:38:11 CEST 2002 ide-clean-62
>>
>>- Add missing locking around ide_do_request in do_ide_request().
>
>
> This is broken, do_ide_request() is already called with the request lock
> held. tq_disk run -> generic_unplug_device (grab lock) ->
> __generic_unplug_device -> do_ide_request(). You just introduced a
> deadlock.
>
> This code would have caused hangs or massive corruption immediately if
> ide_lock wasn't ready held there. Not to mention instant spin_unlock
> BUG() triggers in queue_command()
>

Oops. Indeed I see now that the ide_lock is exported to
the upper layers above it in ide-probe.c

blk_init_queue(q, do_ide_request, &ide_lock);

But this is problematic in itself, since it means that
we are basically serialiazing between *all* requests
on all channels.

So I think we should have per channel locks on this level
right? This is anyway our unit for serialization.
(I'm just surprised that blk_init_queue() doesn't
provide queue specific locking and relies on exported
locks from the drivers...)