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Subject[PATCH v3 02/15] smp: Create a new function to shutdown nonboot cpus
Date
This function will be used later in machine_shutdown() for some archs.

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>
CC: Thomas Gleixner <tglx@linutronix.de>
CC: Josh Poimboeuf <jpoimboe@redhat.com>
CC: "Peter Zijlstra (Intel)" <peterz@infradead.org>
CC: Jiri Kosina <jkosina@suse.cz>
CC: Nicholas Piggin <npiggin@gmail.com>
CC: Daniel Lezcano <daniel.lezcano@linaro.org>
CC: Ingo Molnar <mingo@kernel.org>
CC: Eiichi Tsukata <devel@etsukata.com>
CC: Zhenzhong Duan <zhenzhong.duan@oracle.com>
CC: Nadav Amit <namit@vmware.com>
CC: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
CC: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
CC: Tony Luck <tony.luck@intel.com>
CC: Fenghua Yu <fenghua.yu@intel.com>
CC: Russell King <linux@armlinux.org.uk>
CC: Catalin Marinas <catalin.marinas@arm.com>
CC: Will Deacon <will@kernel.org>
CC: linux-arm-kernel@lists.infradead.org
CC: linux-ia64@vger.kernel.org
CC: linux-kernel@vger.kernel.org
---
include/linux/cpu.h | 2 ++
kernel/cpu.c | 42 ++++++++++++++++++++++++++++++++++++++++++
2 files changed, 44 insertions(+)

diff --git a/include/linux/cpu.h b/include/linux/cpu.h
index cf8cf38dca43..64a246e9c8db 100644
--- 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 069802f7010f..03c727195b65 100644
--- 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*/
--
2.17.1
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