cpu/hotplug: Provide bringup_hibernate_cpu()

arm64 uses cpu_up() in the resume from hibernation code to ensure that the
CPU on which the system hibernated is online. Provide a core function for
this.

[ tglx: Split out from the combo arm64 patch ]

Signed-off-by: Qais Yousef <qais.yousef@arm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Link: https://lkml.kernel.org/r/20200323135110.30522-9-qais.yousef@arm.com

diff --git a/include/linux/cpu.h b/include/linux/cpu.h
index 64a246e..9dc1e89 100644 (file)
--- a/include/linux/cpu.h
+++ b/include/linux/cpu.h
@@ -93,6 +93,7 @@ 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);
+int bringup_hibernate_cpu(unsigned int sleep_cpu);
 
 #else  /* CONFIG_SMP */
 #define cpuhp_tasks_frozen     0

diff --git a/kernel/cpu.c b/kernel/cpu.c
index 03c7271..f803678 100644 (file)
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -1275,6 +1275,29 @@ int add_cpu(unsigned int cpu)
 }
 EXPORT_SYMBOL_GPL(add_cpu);
 
+/**
+ * bringup_hibernate_cpu - Bring up the CPU that we hibernated on
+ * @sleep_cpu: The cpu we hibernated on and should be brought up.
+ *
+ * On some architectures like arm64, we can hibernate on any CPU, but on
+ * wake up the CPU we hibernated on might be offline as a side effect of
+ * using maxcpus= for example.
+ */
+int bringup_hibernate_cpu(unsigned int sleep_cpu)
+{
+       int ret;
+
+       if (!cpu_online(sleep_cpu)) {
+               pr_info("Hibernated on a CPU that is offline! Bringing CPU up.\n");
+               ret = cpu_up(sleep_cpu);
+               if (ret) {
+                       pr_err("Failed to bring hibernate-CPU up!\n");
+                       return ret;
+               }
+       }
+       return 0;
+}
+
 #ifdef CONFIG_PM_SLEEP_SMP
 static cpumask_var_t frozen_cpus;