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Subject[tip: smp/core] cpu/hotplug: Provide bringup_hibernate_cpu()
The following commit has been merged into the smp/core branch of tip:

Commit-ID: d720f98604391dab6aa3cb4c1bc005ed1aba4703
Gitweb: https://git.kernel.org/tip/d720f98604391dab6aa3cb4c1bc005ed1aba4703
Author: Qais Yousef <qais.yousef@arm.com>
AuthorDate: Mon, 23 Mar 2020 13:51:01
Committer: Thomas Gleixner <tglx@linutronix.de>
CommitterDate: Wed, 25 Mar 2020 12:59:34 +01:00

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

---
include/linux/cpu.h | 1 +
kernel/cpu.c | 23 +++++++++++++++++++++++
2 files changed, 24 insertions(+)

diff --git a/include/linux/cpu.h b/include/linux/cpu.h
index 64a246e..9dc1e89 100644
--- 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
--- 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;

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