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Mon, 14 Sep 2020 19:49:23 -0700 (PDT) Received: from localhost ([203.185.249.227]) by smtp.gmail.com with ESMTPSA id a9sm10556060pjm.40.2020.09.14.19.49.22 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 14 Sep 2020 19:49:23 -0700 (PDT) Date: Tue, 15 Sep 2020 12:49:17 +1000 From: Nicholas Piggin Subject: Re: [PATCH v2 3/4] sparc64: remove mm_cpumask clearing to fix kthread_use_mm race To: Anatoly Pugachev References: <20200914045219.3736466-1-npiggin@gmail.com> <20200914045219.3736466-4-npiggin@gmail.com> <1600066040.vnmz9nxhwt.astroid@bobo.none> In-Reply-To: MIME-Version: 1.0 Message-Id: <1600138100.0flxk0qjzs.astroid@bobo.none> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Jens Axboe , linux-arch@vger.kernel.org, Peter Zijlstra , "Aneesh Kumar K . V" , Linux Kernel list , linux-mm@kvack.org, Sparc kernel list , Andrew Morton , linuxppc-dev@lists.ozlabs.org, "David S . Miller" Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" Excerpts from Anatoly Pugachev's message of September 14, 2020 8:23 pm: > On Mon, Sep 14, 2020 at 10:00 AM Nicholas Piggin wrot= e: >> >> Excerpts from Nicholas Piggin's message of September 14, 2020 2:52 pm: >> >> [...] >> >> > The basic fix for sparc64 is to remove its mm_cpumask clearing code. T= he >> > optimisation could be effectively restored by sending IPIs to mm_cpuma= sk >> > members and having them remove themselves from mm_cpumask. This is mor= e >> > tricky so I leave it as an exercise for someone with a sparc64 SMP. >> > powerpc has a (currently similarly broken) example. >> >> So this compiles and boots on qemu, but qemu does not support any >> sparc64 machines with SMP. Attempting some simple hacks doesn't get >> me far because openbios isn't populating an SMP device tree, which >> blows up everywhere. >> >> The patch is _relatively_ simple, hopefully it shouldn't explode, so >> it's probably ready for testing on real SMP hardware, if someone has >> a few cycles. >=20 > Nick, >=20 > applied this patch to over 'v5.9-rc5' tag , used my test VM (ldom) > with 32 vcpus. > Machine boot, stress-ng test ( run as > "stress-ng --cpu 8 --io 8 --vm 8 --vm-bytes 2G --fork 8 --timeout 15m" ) > finishes without errors. >=20 Thank you very much Anatoly. Thanks, Nick