* [RFC][PATCH] rcu: Use WRITE_ONCE in RCU_INIT_POINTER
@ 2015-06-02 15:26 Peter Zijlstra
2015-06-02 16:25 ` Paul E. McKenney
0 siblings, 1 reply; 2+ messages in thread
From: Peter Zijlstra @ 2015-06-02 15:26 UTC (permalink / raw)
To: Paul McKenney; +Cc: josh, rostedt, mathieu.desnoyers, laijs, linux-kernel
For the paranoid amongst us GCC would be in its right to use byte stores
to write our NULL value, tell it not to do that.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
include/linux/rcupdate.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index 33a056bb886f..e173847b6543 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -1046,7 +1046,7 @@ static inline notrace void rcu_read_unlock_sched_notrace(void)
#define RCU_INIT_POINTER(p, v) \
do { \
rcu_dereference_sparse(p, __rcu); \
- p = RCU_INITIALIZER(v); \
+ WRITE_ONCE(p, RCU_INITIALIZER(v)); \
} while (0)
/**
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [RFC][PATCH] rcu: Use WRITE_ONCE in RCU_INIT_POINTER
2015-06-02 15:26 [RFC][PATCH] rcu: Use WRITE_ONCE in RCU_INIT_POINTER Peter Zijlstra
@ 2015-06-02 16:25 ` Paul E. McKenney
0 siblings, 0 replies; 2+ messages in thread
From: Paul E. McKenney @ 2015-06-02 16:25 UTC (permalink / raw)
To: Peter Zijlstra; +Cc: josh, rostedt, mathieu.desnoyers, laijs, linux-kernel
On Tue, Jun 02, 2015 at 05:26:48PM +0200, Peter Zijlstra wrote:
>
> For the paranoid amongst us GCC would be in its right to use byte stores
> to write our NULL value, tell it not to do that.
>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Good point, queued for 4.3.
Thanx, Paul
> ---
> include/linux/rcupdate.h | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
> index 33a056bb886f..e173847b6543 100644
> --- a/include/linux/rcupdate.h
> +++ b/include/linux/rcupdate.h
> @@ -1046,7 +1046,7 @@ static inline notrace void rcu_read_unlock_sched_notrace(void)
> #define RCU_INIT_POINTER(p, v) \
> do { \
> rcu_dereference_sparse(p, __rcu); \
> - p = RCU_INITIALIZER(v); \
> + WRITE_ONCE(p, RCU_INITIALIZER(v)); \
> } while (0)
>
> /**
>
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