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@xxxxxxxxx>
---
arch/powerpc/Kconfig | 4 ++++
include/linux/cpu.h | 7 ++++++-
kernel/cpu.c | 10 +++++++++-
kernel/power/Kconfig | 9 +++++++++
4 files changed, 28 insertions(+), 2 deletions(-)
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 2d0be82c3061..bc98b0e37a10 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -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
diff --git a/include/linux/cpu.h b/include/linux/cpu.h
index 563e697e7779..dd3813959d62 100644
--- a/include/linux/cpu.h
+++ b/include/linux/cpu.h
@@ -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)
{
diff --git a/kernel/cpu.c b/kernel/cpu.c
index 6754f3ecfd94..d1bf6e2b4752 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 f8fe57d1022e..9bbaaab14b36 100644
--- a/kernel/power/Kconfig
+++ b/kernel/power/Kconfig
@@ -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
--
2.20.1
