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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Thu, 9 Jun 2016 21:55:40 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	"Sell, Timothy C" <Timothy.Sell@...sys.com>
cc:	"corbet@....net" <corbet@....net>,
	"mingo@...hat.com" <mingo@...hat.com>,
	"hpa@...or.com" <hpa@...or.com>,
	"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
	"Arfvidson, Erik" <Erik.Arfvidson@...sys.com>,
	"hofrat@...dl.org" <hofrat@...dl.org>,
	"dzickus@...hat.com" <dzickus@...hat.com>,
	"jes.sorensen@...hat.com" <jes.sorensen@...hat.com>,
	"Curtin, Alexander Paul" <Alexander.Curtin@...sys.com>,
	"janani.rvchndrn@...il.com" <janani.rvchndrn@...il.com>,
	"sudipm.mukherjee@...il.com" <sudipm.mukherjee@...il.com>,
	"prarit@...hat.com" <prarit@...hat.com>,
	"Binder, David Anthony" <David.Binder@...sys.com>,
	"nhorman@...hat.com" <nhorman@...hat.com>,
	"dan.j.williams@...el.com" <dan.j.williams@...el.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
	"driverdev-devel@...uxdriverproject.org" 
	<driverdev-devel@...uxdriverproject.org>,
	*S-Par-Maintainer <SParMaintainer@...sys.com>,
	"Kershner, David A" <David.Kershner@...sys.com>
Subject: RE: [PATCH v4 09/29] staging: unisys: visorinput: remove unnecessary
 locking

On Thu, 9 Jun 2016, Sell, Timothy C wrote:
> > From: Thomas Gleixner [mailto:tglx@...utronix.de]
> >
> > 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