RE: [PATCH 11/17] net/iavf: use previous value atomic fetch operations

[Ruifeng Wang <Ruifeng.Wang@arm.com>]

> -----Original Message-----
> From: Tyler Retzlaff <roretzla@linux.microsoft.com>
> Sent: Thursday, March 2, 2023 8:48 AM
> To: dev@dpdk.org
> Cc: Honnappa Nagarahalli <Honnappa.Nagarahalli@arm.com>; thomas@monjalon.net; Tyler
> Retzlaff <roretzla@linux.microsoft.com>
> Subject: [PATCH 11/17] net/iavf: use previous value atomic fetch operations
> 
> Use __atomic_fetch_{add,and,or,sub,xor} instead of __atomic_{add,and,or,sub,xor}_fetch
> when we have no interest in the result of the operation.
> 
> Reduces unnecessary codegen that provided the result of the atomic operation that was not
> used.
> 
> Change brings closer alignment with atomics available in C11 standard and will reduce
> review effort when they are integrated.
> 
> Signed-off-by: Tyler Retzlaff <roretzla@linux.microsoft.com>
> ---
>  drivers/net/iavf/iavf_vchnl.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/net/iavf/iavf_vchnl.c b/drivers/net/iavf/iavf_vchnl.c index
> 9adaadb..73875d7 100644
> --- a/drivers/net/iavf/iavf_vchnl.c
> +++ b/drivers/net/iavf/iavf_vchnl.c
> @@ -128,7 +128,7 @@ struct iavf_event_handler {
>  	int err = pipe(handler->fd);
>  #endif
>  	if (err != 0) {
> -		__atomic_sub_fetch(&handler->ndev, 1, __ATOMIC_RELAXED);
> +		__atomic_fetch_sub(&handler->ndev, 1, __ATOMIC_RELAXED);
>  		return -1;
>  	}
> 
> @@ -137,7 +137,7 @@ struct iavf_event_handler {
> 
>  	if (rte_ctrl_thread_create(&handler->tid, "iavf-event-thread",
>  				NULL, iavf_dev_event_handle, NULL)) {
> -		__atomic_sub_fetch(&handler->ndev, 1, __ATOMIC_RELAXED);
> +		__atomic_fetch_sub(&handler->ndev, 1, __ATOMIC_RELAXED);
>  		return -1;
>  	}
> 
> @@ -533,7 +533,7 @@ struct iavf_event_handler {
>  				/* read message and it's expected one */
>  				if (msg_opc == vf->pend_cmd) {
>  					uint32_t cmd_count =
> -					__atomic_sub_fetch(&vf->pend_cmd_count,
> +					__atomic_fetch_sub(&vf->pend_cmd_count,

It doesn't apply here. The return value is used.
The rest of the series looks good to me.

>  							1, __ATOMIC_RELAXED);
>  					if (cmd_count == 0)
>  						_notify_cmd(vf, msg_ret);
> --
> 1.8.3.1