Re: [PATCH RESEND 2/3 v2.6.39-rc7] block: make disk_block_events() properly wait for work cancellation

[Tejun Heo <tj@kernel.org>]

Hello,

On Wed, May 18, 2011 at 02:46:30AM -0700, Linus Torvalds wrote:
> Quite frankly. right now I think I need to just release 2.6.39, and
> then for 2.6.40 merge the trivial
> 
>   mutex_lock(&ev->mutex);
>   if (!ev->block++)
>     cancel_delayed_work_sync(&ev->dwork);
>   mutex_unlock(&ev->mutex);
> 
> with a cc: stable for backporting.

This isn't super-critical and releasing without the fix but later
backporting via -stable definitely is an option.

> So we can't be in some atomic context inside some other spinlock
> anyway, afaik. And there can be no lock order issues, since this
> would always be a new inner lock.

Yeap, the problem was unblock/check being allowed to be called without
sleeping context, which isn't used anymore and was broken due to
cancellation race.  We can just enclose the whole thing inside per-ev
mutex and everything should be simple and fine.  I'll post patches
soon.

Thanks.

-- 
tejun