[PATCH 17/19] xen: don't free percpu areas during suspend

[Mykyta Poturai <Mykyta_Poturai@xxxxxxxx>]

From: Juergen Gross <jgross@xxxxxxxx>

Instead of freeing percpu areas during suspend and allocating them
again when resuming keep them. Only free an area in case a cpu didn't
come up again when resuming.

It should be noted that there is a potential change in behaviour as
the percpu areas are no longer zeroed out during suspend/resume. While
I have checked the called cpu notifier hooks to cope with that there
might be some well hidden dependency on the previous behaviour. OTOH
a component not registering itself for cpu down/up and expecting to
see a zeroed percpu variable after suspend/resume is kind of broken
already. And the opposite case, where a component is not registered
to be called for cpu down/up and is not expecting a percpu variable
suddenly to be zero due to suspend/resume is much more probable,
especially as the suspend/resume functionality seems not to be tested
that often.

Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
Reviewed-by: Dario Faggioli <dfaggioli@xxxxxxxx>
---
 xen/arch/arm/percpu.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/xen/arch/arm/percpu.c b/xen/arch/arm/percpu.c
index 25442c48fe..0642705544 100644
--- a/xen/arch/arm/percpu.c
+++ b/xen/arch/arm/percpu.c
@@ -58,10 +58,13 @@ static int cpu_percpu_callback(
     switch ( action )
     {
     case CPU_UP_PREPARE:
+      if ( system_state != SYS_STATE_resume )
         rc = init_percpu_area(cpu);
         break;
     case CPU_UP_CANCELED:
     case CPU_DEAD:
+    case CPU_RESUME_FAILED:
+      if ( system_state != SYS_STATE_suspend )
         free_percpu_area(cpu);
         break;
     default:
-- 
2.37.1