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Fri, 27 Nov 2020 01:49:43 -0800 (PST) Date: Fri, 27 Nov 2020 09:49:40 +0000 From: Quentin Perret To: Will Deacon Subject: Re: [PATCH v4 07/14] sched: Introduce restrict_cpus_allowed_ptr() to limit task CPU affinity Message-ID: <20201127094940.GA906877@google.com> References: <20201124155039.13804-1-will@kernel.org> <20201124155039.13804-8-will@kernel.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20201124155039.13804-8-will@kernel.org> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20201127_044947_098334_72B681D4 X-CRM114-Status: GOOD ( 17.71 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-arch@vger.kernel.org, Marc Zyngier , kernel-team@android.com, Vincent Guittot , Juri Lelli , Ingo Molnar , Peter Zijlstra , Catalin Marinas , Johannes Weiner , linux-kernel@vger.kernel.org, Qais Yousef , Li Zefan , Greg Kroah-Hartman , Tejun Heo , Suren Baghdasaryan , Morten Rasmussen , linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Tuesday 24 Nov 2020 at 15:50:32 (+0000), Will Deacon wrote: > Asymmetric systems may not offer the same level of userspace ISA support > across all CPUs, meaning that some applications cannot be executed by > some CPUs. As a concrete example, upcoming arm64 big.LITTLE designs do > not feature support for 32-bit applications on both clusters. > > Although userspace can carefully manage the affinity masks for such > tasks, one place where it is particularly problematic is execve() > because the CPU on which the execve() is occurring may be incompatible > with the new application image. In such a situation, it is desirable to > restrict the affinity mask of the task and ensure that the new image is > entered on a compatible CPU. From userspace's point of view, this looks > the same as if the incompatible CPUs have been hotplugged off in its > affinity mask. > > In preparation for restricting the affinity mask for compat tasks on > arm64 systems without uniform support for 32-bit applications, introduce > a restrict_cpus_allowed_ptr(), which allows the current affinity mask > for a task to be shrunk to the intersection of a parameter mask. > > Signed-off-by: Will Deacon Reviewed-by: Quentin Perret Thanks, Quentin _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel