Re: [PATCH rdma-core 4/6] rdmacm: Use C11 stdatomic for all atomics

[Bart Van Assche <Bart.VanAssche-XdAiOPVOjttBDgjK7y7TUQ@public.gmane.org>]

On Wed, 2017-03-15 at 16:12 -0600, Jason Gunthorpe wrote:
> @@ -1013,7 +1012,7 @@ int close(int socket)
>  			return ret;
>  	}
>  
> -	if (atomic_dec(&fdi->refcnt))
> +	if (atomic_fetch_sub(&fdi->refcnt, 1))
>  		return 0;
>  
>  	idm_clear(&idm, socket);
> @@ -898,7 +898,7 @@ static int rs_create_ep(struct rsocket *rs)
>  
>  static void rs_release_iomap_mr(struct rs_iomap_mr *iomr)
>  {
> -	if (atomic_dec(&iomr->refcnt))
> +	if (atomic_fetch_sub(&iomr->refcnt, 1))
>  		return;
>  
>  	dlist_remove(&iomr->entry);

Hello Jason,

In the gcc documentation I read that __sync_sub_and_fetch() (used to
implement atomic_dec()) returns the new value. In the C11 standard I read
that atomic_fetch_sub() returns the old value. Do you agree with this?

Thanks,

Bart.--
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