Re: [PATCH next 3/5] locking/osq_lock: Clarify osq_wait_next()

[Waiman Long <longman@redhat.com>]

On 12/29/23 15:56, David Laight wrote:
> osq_wait_next() is passed 'prev' from osq_lock() and NULL from osq_unlock()
> but only needs the 'cpu' value to write to lock->tail.
> Just pass prev->cpu or OSQ_UNLOCKED_VAL instead.
>
> Also directly return NULL or 'next' instead of breaking the loop.
>
> Should have no effect on the generated code since gcc manages to
> assume that 'prev != NULL' due to an earlier dereference.
>
> Signed-off-by: David Laight <david.laight@aculab.com>
> ---
>   kernel/locking/osq_lock.c | 23 ++++++++++-------------
>   1 file changed, 10 insertions(+), 13 deletions(-)
>
> diff --git a/kernel/locking/osq_lock.c b/kernel/locking/osq_lock.c
> index 55f5db896c02..9bb3a077ba92 100644
> --- a/kernel/locking/osq_lock.c
> +++ b/kernel/locking/osq_lock.c
> @@ -48,18 +48,17 @@ static inline struct optimistic_spin_node *decode_cpu(int encoded_cpu_val)
>   static inline struct optimistic_spin_node *
>   osq_wait_next(struct optimistic_spin_queue *lock,
>   	      struct optimistic_spin_node *node,
> -	      struct optimistic_spin_node *prev)
> +	      int old)

Make the last argument name more descriptive, like "old_cpu" as the 
"int" type does not provide enough context to allow people to guess what 
"old" may be.

Cheers,
Longman