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Commit 4c0b4bc6 authored by Davidlohr Bueso's avatar Davidlohr Bueso Committed by Paolo Bonzini
Browse files

kvm,mips: Fix potential swait_active() races 



For example, the following could occur, making us miss a wakeup:

CPU0					CPU1
kvm_vcpu_block				kvm_mips_comparecount_func
					  [L] swait_active(&vcpu->wq)
  [S] prepare_to_swait(&vcpu->wq)
  [L] if (!kvm_vcpu_has_pending_timer(vcpu))
         schedule()                       [S] queue_timer_int(vcpu)

Ensure that the swait_active() check is not hoisted over the interrupt.

Signed-off-by: default avatarDavidlohr Bueso <dbueso@suse.de>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 267ad7bc

arch/mips/kvm/mips.c

+2 −2
Original line number Diff line number Diff line
@@ -514,7 +514,7 @@ int kvm_vcpu_ioctl_interrupt(struct kvm_vcpu *vcpu, 


	dvcpu->arch.wait = 0;



	if (swait_active(&dvcpu->wq))

	if (swq_has_sleeper(&dvcpu->wq))

		swake_up(&dvcpu->wq);



	return 0;
@@ -1179,7 +1179,7 @@ static void kvm_mips_comparecount_func(unsigned long data) 
	kvm_mips_callbacks->queue_timer_int(vcpu);



	vcpu->arch.wait = 0;

	if (swait_active(&vcpu->wq))

	if (swq_has_sleeper(&vcpu->wq))

		swake_up(&vcpu->wq);

}