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

From: Tejun Heo
Date: Wed May 18 2011 - 06:05:00 EST


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


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