[v4,4/6] xen: don't free percpu areas during suspend
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Message ID 20190402161910.14860-5-jgross@suse.com
State New, archived
Headers show
Series
  • xen: simplify suspend/resume handling
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Commit Message

Juergen Gross April 2, 2019, 4:19 p.m. UTC
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@suse.com>
Reviewed-by: Dario Faggioli <dfaggioli@suse.com>
Acked-by: Jan Beulich <jbeulich@suse.com>
---
 xen/arch/x86/percpu.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

Patch
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diff --git a/xen/arch/x86/percpu.c b/xen/arch/x86/percpu.c
index 8be4ebddf4..5ea14b6ec3 100644
--- a/xen/arch/x86/percpu.c
+++ b/xen/arch/x86/percpu.c
@@ -76,7 +76,8 @@  static int cpu_percpu_callback(
         break;
     case CPU_UP_CANCELED:
     case CPU_DEAD:
-        if ( !park_offline_cpus )
+    case CPU_RESUME_FAILED:
+        if ( !park_offline_cpus && system_state != SYS_STATE_suspend )
             free_percpu_area(cpu);
         break;
     case CPU_REMOVE: