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[tip/core/rcu,04/17] rcu: Add a gcc-style structure initializer for RCU pointers

Message ID 1340379312-6684-4-git-send-email-paulmck@linux.vnet.ibm.com
State Accepted
Commit 172708d002e0a2aca032b04fe6f2b8525c29244a
Headers show

Commit Message

Paul E. McKenney June 22, 2012, 3:34 p.m. UTC 
From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>

RCU_INIT_POINTER() returns a value that is never used, and which should
be abolished due to terminal ugliness:

	q = RCU_INIT_POINTER(global_p, p);

However, there are two uses that cannot be handled by a do-while
formulation because they do gcc-style initialization:

	RCU_INIT_POINTER(.real_cred, &init_cred),
	RCU_INIT_POINTER(.cred, &init_cred),

This usage is clever, but not necessarily the nicest approach.
This commit therefore creates an RCU_POINTER_INITIALIZER() macro that
is specifically designed for gcc-style initialization.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
---
 include/linux/rcupdate.h |    8 ++++++++
 1 files changed, 8 insertions(+), 0 deletions(-)

Comments

David Howells June 22, 2012, 4:02 p.m. UTC | #1 
Paul E. McKenney <paulmck@linux.vnet.ibm.com> wrote:

> RCU_INIT_POINTER() returns a value that is never used, and which should
> be abolished due to terminal ugliness:
> 
> 	q = RCU_INIT_POINTER(global_p, p);
> 
> However, there are two uses that cannot be handled by a do-while
> formulation because they do gcc-style initialization:
> 
> 	RCU_INIT_POINTER(.real_cred, &init_cred),
> 	RCU_INIT_POINTER(.cred, &init_cred),
> 
> This usage is clever, but not necessarily the nicest approach.
> This commit therefore creates an RCU_POINTER_INITIALIZER() macro that
> is specifically designed for gcc-style initialization.
> 
> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

Acked-by: David Howells <dhowells@redhat.com>
diff mbox

Patch

diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index 26d1a47..88e4e08 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -906,6 +906,14 @@  static inline notrace void rcu_read_unlock_sched_notrace(void)
 #define RCU_INIT_POINTER(p, v) \
 		p = (typeof(*v) __force __rcu *)(v)
 
+/**
+ * RCU_POINTER_INITIALIZER() - statically initialize an RCU protected pointer
+ *
+ * GCC-style initialization for an RCU-protected pointer in a structure field.
+ */
+#define RCU_POINTER_INITIALIZER(p, v) \
+		.p = (typeof(*v) __force __rcu *)(v)
+
 static __always_inline bool __is_kfree_rcu_offset(unsigned long offset)
 {
 	return offset < 4096;