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McKenney" To: Qais Yousef Subject: Re: [PATCH v4 01/17] cpu: Add new {add,remove}_cpu() functions Message-ID: <20200323150034.GG3199@paulmck-ThinkPad-P72> References: <20200323135110.30522-1-qais.yousef@arm.com> <20200323135110.30522-2-qais.yousef@arm.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20200323135110.30522-2-qais.yousef@arm.com> User-Agent: Mutt/1.9.4 (2018-02-28) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200323_080036_303553_48276A2C X-CRM114-Status: GOOD ( 16.99 ) 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: , Reply-To: paulmck@kernel.org Cc: Juergen Gross , Mark Rutland , Lorenzo Pieralisi , linux-parisc@vger.kernel.org, Michael Ellerman , Helge Deller , x86@kernel.org, linux-kernel@vger.kernel.org, sparclinux@vger.kernel.org, xen-devel@lists.xenproject.org, Thomas Gleixner , linuxppc-dev@lists.ozlabs.org, "David S. Miller" , 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+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Mon, Mar 23, 2020 at 01:50:54PM +0000, Qais Yousef wrote: > The new functions use device_{online,offline}() which are userspace > safe. > > This is in preparation to move cpu_{up, down} kernel users to use > a safer interface that is not racy with userspace. > > Suggested-by: "Paul E. McKenney" > Signed-off-by: Qais Yousef > CC: Thomas Gleixner > CC: "Paul E. McKenney" Reviewed-by: Paul E. McKenney > CC: Helge Deller > CC: Michael Ellerman > CC: "David S. Miller" > CC: Juergen Gross > CC: Mark Rutland > CC: Lorenzo Pieralisi > CC: xen-devel@lists.xenproject.org > CC: linux-parisc@vger.kernel.org > CC: sparclinux@vger.kernel.org > CC: linuxppc-dev@lists.ozlabs.org > CC: linux-arm-kernel@lists.infradead.org > CC: x86@kernel.org > CC: linux-kernel@vger.kernel.org > --- > include/linux/cpu.h | 2 ++ > kernel/cpu.c | 24 ++++++++++++++++++++++++ > 2 files changed, 26 insertions(+) > > diff --git a/include/linux/cpu.h b/include/linux/cpu.h > index 1ca2baf817ed..cf8cf38dca43 100644 > --- a/include/linux/cpu.h > +++ b/include/linux/cpu.h > @@ -89,6 +89,7 @@ extern ssize_t arch_cpu_release(const char *, size_t); > #ifdef CONFIG_SMP > extern bool cpuhp_tasks_frozen; > int cpu_up(unsigned int cpu); > +int add_cpu(unsigned int cpu); > void notify_cpu_starting(unsigned int cpu); > extern void cpu_maps_update_begin(void); > extern void cpu_maps_update_done(void); > @@ -118,6 +119,7 @@ extern void cpu_hotplug_disable(void); > extern void cpu_hotplug_enable(void); > void clear_tasks_mm_cpumask(int cpu); > int cpu_down(unsigned int cpu); > +int remove_cpu(unsigned int cpu); > > #else /* CONFIG_HOTPLUG_CPU */ > > diff --git a/kernel/cpu.c b/kernel/cpu.c > index 9c706af713fb..069802f7010f 100644 > --- a/kernel/cpu.c > +++ b/kernel/cpu.c > @@ -1057,6 +1057,18 @@ int cpu_down(unsigned int cpu) > } > EXPORT_SYMBOL(cpu_down); > > +int remove_cpu(unsigned int cpu) > +{ > + int ret; > + > + lock_device_hotplug(); > + ret = device_offline(get_cpu_device(cpu)); > + unlock_device_hotplug(); > + > + return ret; > +} > +EXPORT_SYMBOL_GPL(remove_cpu); > + > #else > #define takedown_cpu NULL > #endif /*CONFIG_HOTPLUG_CPU*/ > @@ -1209,6 +1221,18 @@ int cpu_up(unsigned int cpu) > } > EXPORT_SYMBOL_GPL(cpu_up); > > +int add_cpu(unsigned int cpu) > +{ > + int ret; > + > + lock_device_hotplug(); > + ret = device_online(get_cpu_device(cpu)); > + unlock_device_hotplug(); > + > + return ret; > +} > +EXPORT_SYMBOL_GPL(add_cpu); > + > #ifdef CONFIG_PM_SLEEP_SMP > static cpumask_var_t frozen_cpus; > > -- > 2.17.1 > _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel