kernel/cpu: Allow non-zero CPU to be primary for suspend / kexec freeze
This patch provides an arch option, ARCH_SUSPEND_NONZERO_CPU, to
opt-in to allowing suspend to occur on one of the housekeeping CPUs
rather than hardcoded CPU0.
This will allow CPU0 to be a nohz_full CPU with a later change.
It may be possible for platforms with hardware/firmware restrictions
on suspend/wake effectively support this by handing off the final
stage to CPU0 when kernel housekeeping is no longer required. Another
option is to make housekeeping / nohz_full mask dynamic at runtime,
but the complexity could not be justified at this time.
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rafael J . Wysocki <rafael.j.wysocki@intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linuxppc-dev@lists.ozlabs.org
Link: https://lkml.kernel.org/r/20190411033448.20842-4-npiggin@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
diff --git a/kernel/cpu.c b/kernel/cpu.c
index 6754f3e..d1bf6e2 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -9,6 +9,7 @@
#include <linux/notifier.h>
#include <linux/sched/signal.h>
#include <linux/sched/hotplug.h>
+#include <linux/sched/isolation.h>
#include <linux/sched/task.h>
#include <linux/sched/smt.h>
#include <linux/unistd.h>
@@ -1199,8 +1200,15 @@ int freeze_secondary_cpus(int primary)
int cpu, error = 0;
cpu_maps_update_begin();
- if (!cpu_online(primary))
+ if (primary == -1) {
primary = cpumask_first(cpu_online_mask);
+ if (!housekeeping_cpu(primary, HK_FLAG_TIMER))
+ primary = housekeeping_any_cpu(HK_FLAG_TIMER);
+ } else {
+ if (!cpu_online(primary))
+ primary = cpumask_first(cpu_online_mask);
+ }
+
/*
* We take down all of the non-boot CPUs in one shot to avoid races
* with the userspace trying to use the CPU hotplug at the same time
diff --git a/kernel/power/Kconfig b/kernel/power/Kconfig
index f8fe57d..9bbaaab 100644
--- a/kernel/power/Kconfig
+++ b/kernel/power/Kconfig
@@ -114,6 +114,15 @@
depends on PM_SLEEP
select HOTPLUG_CPU
+config PM_SLEEP_SMP_NONZERO_CPU
+ def_bool y
+ depends on PM_SLEEP_SMP
+ depends on ARCH_SUSPEND_NONZERO_CPU
+ ---help---
+ If an arch can suspend (for suspend, hibernate, kexec, etc) on a
+ non-zero numbered CPU, it may define ARCH_SUSPEND_NONZERO_CPU. This
+ will allow nohz_full mask to include CPU0.
+
config PM_AUTOSLEEP
bool "Opportunistic sleep"
depends on PM_SLEEP
