From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Message-ID: <510848E2.50203@wwwdotorg.org> Date: Tue, 29 Jan 2013 15:10:42 -0700 From: Stephen Warren MIME-Version: 1.0 Subject: Re: [PATCH] ARM: call disable_nonboot_cpus() from machine_shutdown() References: <1357160861-26282-1-git-send-email-swarren@wwwdotorg.org> <50E4C9C6.20609@codeaurora.org> <20130103120259.GB5193@mudshark.cambridge.arm.com> <20130103122100.GN2631@n2100.arm.linux.org.uk> <50E5E967.3020805@wwwdotorg.org> <20130106162200.GC11025@mudshark.cambridge.arm.com> <20130106164033.GA3222@n2100.arm.linux.org.uk> <87ehhxahd1.fsf@xmission.com> <50ECB49C.7010609@wwwdotorg.org> <87obgwb5d1.fsf@xmission.com> In-Reply-To: <87obgwb5d1.fsf@xmission.com> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: kexec-bounces@lists.infradead.org Errors-To: kexec-bounces+dwmw2=infradead.org@lists.infradead.org To: "Eric W. Biederman" Cc: Stephen Warren , "kexec@lists.infradead.org" , Stephen Boyd , "linux-kernel@vger.kernel.org" , Will Deacon , Russell King - ARM Linux , "linux-arm-kernel@lists.infradead.org" On 01/10/2013 11:28 PM, Eric W. Biederman wrote: ... > I don't have any problem with generic code in the reboot path > doing: > if (cpu_online(0)) > set_cpus_allowed_ptr(current, cpumask_of(0)); It looks like that API just affects the scheduler, and not whether the other CPUs are actually active/hot-plugged-in. At least for my use-case, I need something that really disables the other CPUs so they aren't executing code, hence my tendency to hot-un-plug them using disable_nonboot_cpus(), rather than just shift task execution off them using the code above. I wonder if all architectures shouldn't always do the following in all reboot/shutdown/kexec cases: * set_cpus_allowed_ptr() to limit code execution to a single CPU. * disable_nonboot_cpus() (or equivalent) if it's available to turn off all the other CPUs. The issue here would be that disable_nonboot_cpus() isn't always available; I assume that's part of the reason that there are arch-specific machine_xxx() hooks, so that architectures can power-off/reset their CPUs even when hotplug isn't enabled? I wonder if that can be refactored so that reboot/poweroff/kexec can share some CPU-disable code with CPU hotplug? _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec