eventfd: Replace rcu_assign_pointer() with RCU_INIT_POINTER()

PATCH In review Andreea-Cristina Bernat 2 participants 2 messages Aug 18, 2014 KVM

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Andreea-Cristina Bernat

author

2014-08-18 15:01 UTC #0 lore raw

PATCH 1/1 eventfd: Replace rcu_assign_pointer() with RCU_INIT_POINTER()

The uses of "rcu_assign_pointer()" are NULLing out the pointers. According to RCU_INIT_POINTER()'s block comment:
"1. This use of RCU_INIT_POINTER() is NULLing out the pointer"
it is better to use it instead of rcu_assign_pointer() because it has a smaller overhead.

The following Coccinelle semantic patch was used:
@@
@@

- rcu_assign_pointer
+ RCU_INIT_POINTER
(..., NULL)

Signed-off-by Andreea-Cristina Bernat <[email protected]>

---
 virt/kvm/eventfd.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

virt/kvm/eventfd.c +3 -3

index 20c3af7..a49130f 100644
@@ -278,7 +278,7 @@ static void irqfd_update(struct kvm *kvm, struct _irqfd *irqfd,
 	struct kvm_kernel_irq_routing_entry *e;
 
 	if (irqfd->gsi >= irq_rt->nr_rt_entries) {
-		rcu_assign_pointer(irqfd->irq_entry, NULL);
+		RCU_INIT_POINTER(irqfd->irq_entry, NULL);
 		return;
 	}

@@ -287,7 +287,7 @@ static void irqfd_update(struct kvm *kvm, struct _irqfd *irqfd,
 		if (e->type == KVM_IRQ_ROUTING_MSI)
 			rcu_assign_pointer(irqfd->irq_entry, e);
 		else
-			rcu_assign_pointer(irqfd->irq_entry, NULL);
+			RCU_INIT_POINTER(irqfd->irq_entry, NULL);
 	}
 }

@@ -473,7 +473,7 @@ kvm_irqfd_deassign(struct kvm *kvm, struct kvm_irqfd *args)
 			 * It is paired with synchronize_srcu done by caller
 			 * of that function.
 			 */
-			rcu_assign_pointer(irqfd->irq_entry, NULL);
+			RCU_INIT_POINTER(irqfd->irq_entry, NULL);
 			irqfd_deactivate(irqfd);
 		}
 	}

Signature · 1 line

1.9.1

Paolo Bonzini

maintainer

2014-08-18 15:06 UTC #1 lore raw

Il 18/08/2014 17:01, Andreea-Cristina Bernat ha scritto:

Quoted 43 lines

The uses of "rcu_assign_pointer()" are NULLing out the pointers. According to RCU_INIT_POINTER()'s block comment:
"1. This use of RCU_INIT_POINTER() is NULLing out the pointer"
it is better to use it instead of rcu_assign_pointer() because it has a smaller overhead.
The following Coccinelle semantic patch was used:
@@
@@
- rcu_assign_pointer
+ RCU_INIT_POINTER
(..., NULL)
Signed-off-by Andreea-Cristina Bernat <[email protected]>
---
 virt/kvm/eventfd.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)
virt/kvm/eventfd.c +2 -2
index 20c3af7..a49130f 100644
@@ -278,7 +278,7 @@ static void irqfd_update(struct kvm *kvm, struct _irqfd *irqfd,
 	struct kvm_kernel_irq_routing_entry *e;
 
 	if (irqfd->gsi >= irq_rt->nr_rt_entries) {
-		rcu_assign_pointer(irqfd->irq_entry, NULL);
+		RCU_INIT_POINTER(irqfd->irq_entry, NULL);
 		return;
 	}
 
@@ -287,7 +287,7 @@ static void irqfd_update(struct kvm *kvm, struct _irqfd *irqfd,
 		if (e->type == KVM_IRQ_ROUTING_MSI)
 			rcu_assign_pointer(irqfd->irq_entry, e);
 		else
-			rcu_assign_pointer(irqfd->irq_entry, NULL);
+			RCU_INIT_POINTER(irqfd->irq_entry, NULL);
 	}
 }
 

virt/kvm/eventfd.c kvm_irqfd_deassign(struct kvm *kvm, struct kvm_irqfd *args) · line 479

Quoted 8 lines

virt/kvm/eventfd.c +1 -1

@@ -473,7 +473,7 @@ kvm_irqfd_deassign(struct kvm *kvm, struct kvm_irqfd *args)
 			 * It is paired with synchronize_srcu done by caller
 			 * of that function.
 			 */
-			rcu_assign_pointer(irqfd->irq_entry, NULL);
+			RCU_INIT_POINTER(irqfd->irq_entry, NULL);
 			irqfd_deactivate(irqfd);
 		}
 	}

Hi, this patch actually had been submitted already last March. It slipped through the cracks. I'm now applying both of Monam Agarwal's RCU_INIT_POINTER patches. Sorry. :)

Thanks,

Paolo