RE: [PATCH v4 09/29] staging: unisys: visorinput: remove unnecessary locking

[Thomas Gleixner]

On Thu, 9 Jun 2016, Sell, Timothy C wrote:
> > From: Thomas Gleixner [mailto:tglx@xxxxxxxxxxxxx]
> >
> > I think I asked this before, but I might have missed the answer.
> > 
> > Why is this a rw_sempahore? It's never taken with down_read and looking
> > at the usage sites it's simply a mutex, right?
> 
> If the semaphore --> mutex change would have been as simple as it sounds,
> we would have had NO problem including it with the next version (v3) of this
> patchset.  But unfortunately, this change uncovered a latent defect, which
> necessitated yet another patch.  (I know... hard to believe that something
> this simple would do that, but it did.)  Rather than further complicating this
> patchset, we thought it would be better to address the visorinput issues via a
> separate follow-on patchset.

That makes me curious. What's the issue? Functional is the mutex the same
thing as the r/w semaphore when the latter is only taken down_write and locked
and released by the same thread, which is the case as far as I can tell.
 
> Is that acceptable for you?

Please fix it before moving the drivers out of staging.

Thanks,

	tglx