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SubjectRe: [PATCH v8 4/4] qrwlock: Use smp_store_release() in write_unlock()
On Thursday, 9 January 2014 01:10:03 UTC+8, Waiman Long  wrote:
> This patch modifies the queue_write_unlock() function to use the
> new smp_store_release() function in another pending patch. It also
> removes the temporary implementation of smp_load_acquire() and
> smp_store_release() function in qrwlock.c.
>
> This patch should only be merged if PeterZ's linux-arch patch patch
> was merged.
>
> Signed-off-by: Waiman Long <Waiman.Long@hp.com>
> Reviewed-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
> ---
> include/asm-generic/qrwlock.h | 4 +---
> kernel/locking/qrwlock.c | 34 ----------------------------------
> 2 files changed, 1 insertions(+), 37 deletions(-)
>
> diff --git a/include/asm-generic/qrwlock.h
b/include/asm-generic/qrwlock.h
> index 2b9a7b4..4d4bd04 100644
> --- a/include/asm-generic/qrwlock.h
> +++ b/include/asm-generic/qrwlock.h
> @@ -179,9 +179,7 @@ static inline void queue_write_unlock(struct
qrwlock *lock)
> /*
> * Make sure that none of the critical section will be leaked out.
> */
> - smp_mb__before_clear_bit();
> - ACCESS_ONCE(lock->cnts.writer) = 0;
> - smp_mb__after_clear_bit();
> + smp_store_release(&lock->cnts.writer, 0)

This will fail compilation, so probably needs further testing with
Peter's load_acquire/store_release barrier patches.

Thanks,
Daniel
--
Daniel J Blueman
Principal Software Engineer, Numascale


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