KVM: avoid unnecessary synchronize_rcu
We dont have to wait for a grace period if there is no oldpid that
we are going to free. putpid also checks for NULL, so this patch
only fences synchronize_rcu.
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
(cherry picked from commit 7103f60de8bed21a0ad5d15d2ad5b7a333dda201)
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 50f9473..aa5057e 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -129,7 +129,8 @@
struct pid *oldpid = vcpu->pid;
struct pid *newpid = get_task_pid(current, PIDTYPE_PID);
rcu_assign_pointer(vcpu->pid, newpid);
- synchronize_rcu();
+ if (oldpid)
+ synchronize_rcu();
put_pid(oldpid);
}
cpu = get_cpu();