lkml.org 
[lkml]   [2003]   [Aug]   [3]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: IDE locking problem
On Sun, Aug 03 2003, Benjamin Herrenschmidt wrote:
> Hi Alan & Bart !
>
> While fixing my hotswap media-bay IDE controller for 2.6, I found
> a locking problem with IDE (again ? :) in ide_unregister_hw. Basically
> the problem is that it calls blk_cleanup_queue(), which is unsafe to
> call with a lock held (it will call flush_workqueue() at one point).
> Other side effect, flush_workqueue() will re-enable IRQs, thus allowing
> us to get an IRQ while holding the spinlock -> double lock, but that's
> just a side effect of calling flush_workqueue in that context.

Irk someone made blk_cleanup_queue() non-atomic. I blame Andrew. And now
it looks like it's impossible to make it atomic again :/. Not very nice,
imo it's preferable to keep such unregister functions atomic.

> So the call to blk_cleanup_queue() shall be moved outside of the
> spinlock. I don't know much about the BIO details, is it possible
> to first unregister_blkdev, then only call blk_cleanup_queue() ? That

That should work, yes.

> would help making sure we don't get a request sneaking in ?

Hmm not really, there's still a chance that could happen.

--
Jens Axboe

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2005-03-22 13:47    [W:0.047 / U:1.060 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site