KVM: Fix kvm_vcpu_block() task state race (e5c239cf) · Commits · 戴 / test

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>

virt/kvm/kvm_main.c

+15 −14

Original line number	Diff line number	Diff line
		@@ -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);
		DEFINE_WAIT(wait);

		add_wait_queue(&vcpu->wq, &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;

		/*
		* 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);
		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)

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