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authorMarcelo Tosatti <mtosatti@redhat.com>2008-05-08 19:47:01 -0300
committerAvi Kivity <avi@qumranet.com>2008-05-18 14:37:12 +0300
commite5c239cfd5b0ec22751c099dbf4d91f3c504a64f (patch)
treed0a63882f0592a4ce23a98478fb9c935213b2e16
parentbd25ed033af52c8c054d43a9cce9c5976266ae74 (diff)
downloadlinux-e5c239cfd5b0ec22751c099dbf4d91f3c504a64f.tar.gz
KVM: Fix kvm_vcpu_block() task state race
There's still a race in kvm_vcpu_block(), if a wake_up_interruptible() call happens before the task state is set to TASK_INTERRUPTIBLE: CPU0 CPU1 kvm_vcpu_block add_wait_queue kvm_cpu_has_interrupt = 0 set interrupt if (waitqueue_active()) wake_up_interruptible() kvm_cpu_has_pending_timer kvm_arch_vcpu_runnable signal_pending set_current_state(TASK_INTERRUPTIBLE) schedule() Can be fixed by using prepare_to_wait() which sets the task state before testing for the wait condition. Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com> Signed-off-by: Avi Kivity <avi@qumranet.com>
-rw-r--r--virt/kvm/kvm_main.c29
1 files changed, 15 insertions, 14 deletions
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index f7ba099049e..2d29e260da3 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -758,25 +758,26 @@ void mark_page_dirty(struct kvm *kvm, gfn_t gfn)
*/
void kvm_vcpu_block(struct kvm_vcpu *vcpu)
{
- DECLARE_WAITQUEUE(wait, current);
-
- add_wait_queue(&vcpu->wq, &wait);
-
- /*
- * We will block until either an interrupt or a signal wakes us up
- */
- while (!kvm_cpu_has_interrupt(vcpu)
- && !kvm_cpu_has_pending_timer(vcpu)
- && !signal_pending(current)
- && !kvm_arch_vcpu_runnable(vcpu)) {
- set_current_state(TASK_INTERRUPTIBLE);
+ DEFINE_WAIT(wait);
+
+ for (;;) {
+ prepare_to_wait(&vcpu->wq, &wait, TASK_INTERRUPTIBLE);
+
+ if (kvm_cpu_has_interrupt(vcpu))
+ break;
+ if (kvm_cpu_has_pending_timer(vcpu))
+ break;
+ if (kvm_arch_vcpu_runnable(vcpu))
+ break;
+ if (signal_pending(current))
+ break;
+
vcpu_put(vcpu);
schedule();
vcpu_load(vcpu);
}
- __set_current_state(TASK_RUNNING);
- remove_wait_queue(&vcpu->wq, &wait);
+ finish_wait(&vcpu->wq, &wait);
}
void kvm_resched(struct kvm_vcpu *vcpu)