From mboxrd@z Thu Jan 1 00:00:00 1970 From: Benjamin Herrenschmidt Subject: Re: [PATCH 2/2] edac: add support for Amazon's Annapurna Labs EDAC Date: Tue, 11 Jun 2019 17:21:39 +1000 Message-ID: <68446361fd1e742b284555b96b638fe6b5218b8b.camel@kernel.crashing.org> References: <1559211329-13098-1-git-send-email-hhhawa@amazon.com> <1559211329-13098-3-git-send-email-hhhawa@amazon.com> <20190531051400.GA2275@cz.tnic> <32431fa2-2285-6c41-ce32-09630205bb54@arm.com> <9a2aaf4a9545ed30568a0613e64bc3f57f047799.camel@kernel.crashing.org> <20190608090556.GA32464@zn.tnic> <1ae5e7a3464f9d8e16b112cd371957ea20472864.camel@kernel.crashing.org> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1ae5e7a3464f9d8e16b112cd371957ea20472864.camel@kernel.crashing.org> Sender: linux-kernel-owner@vger.kernel.org To: Borislav Petkov Cc: James Morse , "Hawa, Hanna" , "robh+dt@kernel.org" , "Woodhouse, David" , "paulmck@linux.ibm.com" , "mchehab@kernel.org" , "mark.rutland@arm.com" , "gregkh@linuxfoundation.org" , "davem@davemloft.net" , "nicolas.ferre@microchip.com" , "devicetree@vger.kernel.org" , "Shenhar, Talel" , "linux-kernel@vger.kernel.org" , "Chocron, Jonathan" , "Krupnik, Ronen" , "linux-edac@vger.kernel.org" , Hanoch, Uri List-Id: devicetree@vger.kernel.org On Tue, 2019-06-11 at 15:50 +1000, Benjamin Herrenschmidt wrote: > On Sat, 2019-06-08 at 11:05 +0200, Borislav Petkov wrote: > > On Sat, Jun 08, 2019 at 10:16:11AM +1000, Benjamin Herrenschmidt wrote: > > > Those IP blocks don't need any SW coordination at runtime. The drivers > > > don't share data nor communicate with each other. There is absolultely > > > no reason to go down that path. > > > > Let me set one thing straight: the EDAC "subsystem" if you will - or > > that pile of code which does error counting and reporting - has its > > limitations in supporting one EDAC driver per platform. And whenever we > > have two drivers loadable on a platform, we have to do dirty hacks like > > > > 301375e76432 ("EDAC: Add owner check to the x86 platform drivers") > > > > What that means is, that if you need to call EDAC logging routines or > > whatnot from two different drivers, there's no locking, no nothing. So > > it might work or it might set your cat on fire. > > Should we fix that then instead ? What are the big issues with adding > some basic locking ? being called from NMIs ? > > If the separate drivers operate on distinct counters I don't see a big > problem there. So looking again ... all the registration/removal of edac devices seem to already be protected by mutexes, so that's not a problem. Tell me more about what specific races you think we might have here, I'm not sure I follow... Cheers, Ben.