Skip to contentSkip to conversation

KVM: use is_idle_task() instead of idle_cpu() to decide when to halt in async_pf

PATCH Applied Gleb Natapov 2 participants 2 messages Nov 28, 2012 – Nov 29, 2012

Subsystems (3)
x86 KVM KVM paravirt
lore
Share & tools
lore

Gleb Natapov

author
#0 lore raw

PATCH 1/1 KVM: use is_idle_task() instead of idle_cpu() to decide when to halt in async_pf

As Frederic pointed idle_cpu() may return false even if async fault happened in the idle task if wake up is pending. In this case the code will try to put idle task to sleep. Fix this by using is_idle_task() to check for idle task.

Reported-by Frederic Weisbecker <[email protected]>
Signed-off-by Gleb Natapov <[email protected]>
arch/x86/kernel/kvm.c +1 -6
index a91c6b4..08b973f 100644
@@ -120,11 +120,6 @@ void kvm_async_pf_task_wait(u32 token)
 	struct kvm_task_sleep_head *b = &async_pf_sleepers[key];
 	struct kvm_task_sleep_node n, *e;
 	DEFINE_WAIT(wait);
-	int cpu, idle;
-
-	cpu = get_cpu();
-	idle = idle_cpu(cpu);
-	put_cpu();
 
 	spin_lock(&b->lock);
 	e = _find_apf_task(b, token);

@@ -138,7 +133,7 @@ void kvm_async_pf_task_wait(u32 token)
 
 	n.token = token;
 	n.cpu = smp_processor_id();
-	n.halted = idle || preempt_count() > 1;
+	n.halted = is_idle_task(current) || preempt_count() > 1;
 	init_waitqueue_head(&n.wq);
 	hlist_add_head(&n.link, &b->list);
 	spin_unlock(&b->lock);

--
Gleb.