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kernel/cpu: Allow non-zero CPU to be primary for suspend / kexec freeze

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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>
This commit is contained in:
Nicholas Piggin 2019-04-11 13:34:46 +10:00 committed by Ingo Molnar
parent 2f1a6fbbef
commit 9ca12ac04b
4 changed files with 28 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
arch/powerpc/Kconfig
View File

@ -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

7
include/linux/cpu.h
View File

@ -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)
{

10
kernel/cpu.c
View File

@ -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

9
kernel/power/Kconfig
View File

@ -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