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authorDavidlohr Bueso <dave@stgolabs.net>2017-09-13 13:08:21 -0700
committerPaolo Bonzini <pbonzini@redhat.com>2017-09-15 16:57:12 +0200
commita0cff57bb2a41cb9cbf13d3203097b4156d8c0ae (patch)
treedb128f5fac2c228a01f314174b20db01b3412316
parentcc1b46803a671047be22f7832ef4a2bb3f63dd94 (diff)
kvm,x86: Fix apf_task_wake_one() wq serialization
During code inspection, the following potential race was seen: CPU0 CPU1 kvm_async_pf_task_wait apf_task_wake_one [L] swait_active(&n->wq) [S] prepare_to_swait(&n.wq) [L] if (!hlist_unhahed(&n.link)) schedule() [S] hlist_del_init(&n->link); Properly serialize swait_active() checks such that a wakeup is not missed. Signed-off-by: Davidlohr Bueso <dbueso@suse.de> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
-rw-r--r--arch/x86/kernel/kvm.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index 874827b0d7ca..aa60a08b65b1 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -180,7 +180,7 @@ static void apf_task_wake_one(struct kvm_task_sleep_node *n)
hlist_del_init(&n->link);
if (n->halted)
smp_send_reschedule(n->cpu);
- else if (swait_active(&n->wq))
+ else if (swq_has_sleeper(&n->wq))
swake_up(&n->wq);
}