Commit 9ca12ac0 authored by Nicholas Piggin's avatar Nicholas Piggin Committed by Ingo Molnar
Browse files

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: default avatarNicholas Piggin <npiggin@gmail.com>
Signed-off-by: default avatarPeter 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: default avatarIngo Molnar <mingo@kernel.org>
parent 2f1a6fbb

arch/powerpc/Kconfig

+4 −0
Original line number Diff line number Diff line
@@ -318,6 +318,10 @@ config ARCH_SUSPEND_POSSIBLE 
		   (PPC_85xx && !PPC_E500MC) || PPC_86xx || PPC_PSERIES \

		   || 44x || 40x



config ARCH_SUSPEND_NONZERO_CPU

	def_bool y

	depends on PPC_POWERNV || PPC_PSERIES



config PPC_DCR_NATIVE

	bool

include/linux/cpu.h

+6 −1
Original line number Diff line number Diff line
@@ -140,7 +140,12 @@ extern void enable_nonboot_cpus(void); 


static inline int suspend_disable_secondary_cpus(void)

{

	return freeze_secondary_cpus(0);

	int cpu = 0;



	if (IS_ENABLED(CONFIG_PM_SLEEP_SMP_NONZERO_CPU))

		cpu = -1;



	return freeze_secondary_cpus(cpu);

}

static inline void suspend_enable_secondary_cpus(void)

{

kernel/cpu.c

+9 −1
Original line number Diff line number Diff line
@@ -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 (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

kernel/power/Kconfig

+9 −0
Original line number Diff line number Diff line
@@ -114,6 +114,15 @@ config PM_SLEEP_SMP 
	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

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