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 <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Cc: Frederic Weisbecker <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Rafael J . Wysocki <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: [email protected]
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>

1 files changed, 6 insertions, 1 deletions

diff --git a/include/linux/cpu.h b/include/linux/cpu.h
index 7ab2f09c0a14..73baab8535c1 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)
 {