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Mon, 14 Sep 2020 20:24:12 -0700 (PDT) Received: from localhost ([203.185.249.227]) by smtp.gmail.com with ESMTPSA id b20sm12442113pfb.198.2020.09.14.20.24.11 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 14 Sep 2020 20:24:12 -0700 (PDT) Date: Tue, 15 Sep 2020 13:24:07 +1000 From: Nicholas Piggin Subject: Re: [PATCH v2 3/4] sparc64: remove mm_cpumask clearing to fix kthread_use_mm race To: David Miller References: <20200914045219.3736466-1-npiggin@gmail.com> <20200914045219.3736466-4-npiggin@gmail.com> <20200914.125942.5644261129883859.davem@davemloft.net> In-Reply-To: <20200914.125942.5644261129883859.davem@davemloft.net> MIME-Version: 1.0 Message-Id: <1600139445.qwycwjuwdq.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: axboe@kernel.dk, linux-arch@vger.kernel.org, peterz@infradead.org, aneesh.kumar@linux.ibm.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, sparclinux@vger.kernel.org, akpm@linux-foundation.org, linuxppc-dev@lists.ozlabs.org Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" Excerpts from David Miller's message of September 15, 2020 5:59 am: > From: Nicholas Piggin > Date: Mon, 14 Sep 2020 14:52:18 +1000 >=20 > ... >> The basic fix for sparc64 is to remove its mm_cpumask clearing code. The >> optimisation could be effectively restored by sending IPIs to mm_cpumask >> members and having them remove themselves from mm_cpumask. This is more >> tricky so I leave it as an exercise for someone with a sparc64 SMP. >> powerpc has a (currently similarly broken) example. >>=20 >> Signed-off-by: Nicholas Piggin >=20 > Sad to see this optimization go away, but what can I do: >=20 > Acked-by: David S. Miller >=20 Thanks Dave, any objection if we merge this via the powerpc tree to keep the commits together? Thanks, Nick