> -----Original Message----- > From: Thomas Gleixner [mailto:tglx@xxxxxxxxxxxxx] > Sent: Thursday, June 09, 2016 5:01 AM > To: Kershner, David A > Cc: corbet@xxxxxxx; mingo@xxxxxxxxxx; hpa@xxxxxxxxx; > gregkh@xxxxxxxxxxxxxxxxxxx; Arfvidson, Erik; Sell, Timothy C; > hofrat@xxxxxxxxx; dzickus@xxxxxxxxxx; jes.sorensen@xxxxxxxxxx; Curtin, > Alexander Paul; janani.rvchndrn@xxxxxxxxx; > sudipm.mukherjee@xxxxxxxxx; prarit@xxxxxxxxxx; Binder, David Anthony; > nhorman@xxxxxxxxxx; dan.j.williams@xxxxxxxxx; linux- > kernel@xxxxxxxxxxxxxxx; linux-doc@xxxxxxxxxxxxxxx; driverdev- > devel@xxxxxxxxxxxxxxxxxxxxxx; *S-Par-Maintainer > Subject: Re: [PATCH v4 09/29] staging: unisys: visorinput: remove > unnecessary locking > > On Wed, 8 Jun 2016, David Kershner wrote: > > + /* > > + * If we're not paused, really enable interrupts. > > + * Regardless of whether we are paused, set a flag indicating > > + * interrupts should be enabled so when we resume, interrupts > > + * will really be enabled. > > + */ > > + down_write(&devdata->lock_visor_dev); > > 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? > > Thanks, > > tglx (Yes, I attempted to address this question in a post I made 6/3/2016 4:30 UTC, which I have basically pasted below.) You are correct that this should be a mutex. We have a local patch that addresses this, but would like to submit this via a follow-on patchset if possible. I'll explain. Rationale: our intent for this patchset was to focus on the visorbus driver ONLY. The only reason visorinput got involved in the first place was due to the visorbus change that necessitated that we remove the locking from visorinput_channel_interrupt(), due to that now being called from atomic context. 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. Is that acceptable for you? Tim Sell -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
