Re: [PATCH v4 01/17] cpu: Add new {add,remove}_cpu() functions
From: "Paul E. McKenney" <paulmck@kernel.org>
Date: 2020-03-23 15:00:38
Also in:
linux-arm-kernel, lkml, sparclinux, xen-devel
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" <paulmck@kernel.org>
Signed-off-by: Qais Yousef <redacted>
CC: Thomas Gleixner <redacted>
CC: "Paul E. McKenney" <paulmck@kernel.org>Reviewed-by: Paul E. McKenney <paulmck@kernel.org>
quoted hunk ↗ jump to hunk
CC: Helge Deller <deller@gmx.de> CC: Michael Ellerman <mpe@ellerman.id.au> CC: "David S. Miller" <davem@davemloft.net> CC: Juergen Gross <jgross@suse.com> CC: Mark Rutland <mark.rutland@arm.com> CC: Lorenzo Pieralisi <redacted> 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