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KVM: avoid unnecessary synchronize_rcu

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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 7103f60de8)
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
This commit is contained in:
Christian Borntraeger
2014-08-19 16:45:56 +02:00
committed by Christoffer Dall
parent 57f984d2c6
commit 7fdbe25673
1 changed files with 2 additions and 1 deletions
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3
virt/kvm/kvm_main.c
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@@ -129,7 +129,8 @@ int vcpu_load(struct kvm_vcpu *vcpu)
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();