From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Return-Path: Sender: Tejun Heo Date: Tue, 10 Apr 2018 07:33:56 -0700 From: "tj@kernel.org" To: Bart Van Assche Cc: "hch@lst.de" , "maxg@mellanox.com" , "israelr@mellanox.com" , "linux-block@vger.kernel.org" , "stable@vger.kernel.org" , "axboe@kernel.dk" , "sagi@grimberg.me" Subject: Re: [PATCH v4] blk-mq: Fix race conditions in request timeout handling Message-ID: <20180410143356.GN3126663@devbig577.frc2.facebook.com> References: <20180410013455.7448-1-bart.vanassche@wdc.com> <20180410142028.GM3126663@devbig577.frc2.facebook.com> <82f1fa6aba4bd5c7684eac6b375776b43b66f8c3.camel@wdc.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <82f1fa6aba4bd5c7684eac6b375776b43b66f8c3.camel@wdc.com> List-ID: Hello, On Tue, Apr 10, 2018 at 02:30:26PM +0000, Bart Van Assche wrote: > > Switching to another model might be better but let's please do that > > with the right rationales. A good portion of this seems to be built > > on misunderstandings. > > Which misunderstandings? I'm not aware of any misunderstandings at my side. > Additionally, tests with two different block drivers (NVMeOF initiator and > the SRP initiator driver) have shown that the current blk-mq timeout > implementation with or without your two patches applied result in subtle and > hard to debug crashes and/or memory corruption. That is not the case for the I must have missed that part. Which tests were they? > patch at the start of this thread. The latest report of a crash I ran into > myself and that is fixed by the patch at the start of this thread is > available here: https://www.spinics.net/lists/linux-rdma/msg63240.html. > > Please also keep in mind that if this patch would be accepted that that does > not prevent this patch to be replaced with an RCU-based solution later on. > If anyone comes up any time with a reliably working RCU-based solution I > will be happy to accept a revert of this patch and I will help reviewing that > RCU-based solution. Oh, switching is fine but let's get in sync first. Who have the repro cases and what were tested? Thanks. -- tejun