cpu/hotplug: Create a new function to shutdown nonboot cpus

This function will be used later in machine_shutdown() for some
architectures.

disable_nonboot_cpus() is not safe to use when doing machine_down(),
because it relies on freeze_secondary_cpus() which in turn is a
suspend/resume related freeze and could abort if the logic detects any
pending activities that can prevent finishing the offlining process.

Signed-off-by: Qais Yousef <qais.yousef@arm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/20200323135110.30522-3-qais.yousef@arm.com

diff --git a/include/linux/cpu.h b/include/linux/cpu.h
index cf8cf38dca43347e4f93ba9da6898191d2981a75..64a246e9c8dbeecbdcb7c2b918ce7a0021a9376b 100644 (file)
--- a/include/linux/cpu.h
+++ b/include/linux/cpu.h
@@ -120,6 +120,7 @@ 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);
+extern void smp_shutdown_nonboot_cpus(unsigned int primary_cpu);
 
 #else /* CONFIG_HOTPLUG_CPU */
 
@@ -131,6 +132,7 @@ static inline int  cpus_read_trylock(void) { return true; }
 static inline void lockdep_assert_cpus_held(void) { }
 static inline void cpu_hotplug_disable(void) { }
 static inline void cpu_hotplug_enable(void) { }
+static inline void smp_shutdown_nonboot_cpus(unsigned int primary_cpu) { }
 #endif /* !CONFIG_HOTPLUG_CPU */
 
 /* Wrappers which go away once all code is converted */

diff --git a/kernel/cpu.c b/kernel/cpu.c
index 069802f7010f24e963e1e372bc44e86826906936..03c727195b65a233071af0d7418bd051e5c67343 100644 (file)
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -1069,6 +1069,48 @@ int remove_cpu(unsigned int cpu)
 }
 EXPORT_SYMBOL_GPL(remove_cpu);
 
+void smp_shutdown_nonboot_cpus(unsigned int primary_cpu)
+{
+       unsigned int cpu;
+       int error;
+
+       cpu_maps_update_begin();
+
+       /*
+        * Make certain the cpu I'm about to reboot on is online.
+        *
+        * This is inline to what migrate_to_reboot_cpu() already do.
+        */
+       if (!cpu_online(primary_cpu))
+               primary_cpu = cpumask_first(cpu_online_mask);
+
+       for_each_online_cpu(cpu) {
+               if (cpu == primary_cpu)
+                       continue;
+
+               error = cpu_down_maps_locked(cpu, CPUHP_OFFLINE);
+               if (error) {
+                       pr_err("Failed to offline CPU%d - error=%d",
+                               cpu, error);
+                       break;
+               }
+       }
+
+       /*
+        * Ensure all but the reboot CPU are offline.
+        */
+       BUG_ON(num_online_cpus() > 1);
+
+       /*
+        * Make sure the CPUs won't be enabled by someone else after this
+        * point. Kexec will reboot to a new kernel shortly resetting
+        * everything along the way.
+        */
+       cpu_hotplug_disabled++;
+
+       cpu_maps_update_done();
+}
+
 #else
 #define takedown_cpu           NULL
 #endif /*CONFIG_HOTPLUG_CPU*/