[1/5] lib/stack: fix inconsistent weak / strong cas
Checks
Commit Message
Fix cmpexchange usage of weak / strong.
The generated code is the same on x86 and ARM (there is no weak
cmpexchange), but the old usage was inconsistent.
For push and pop update size, weak is used because cmpexchange is inside
a loop.
For pop update root, strong is used even though cmpexchange is inside a
loop, because there may be a lot of operations to do in a loop iteration
(locate the new head).
Signed-off-by: Steven Lariau <steven.lariau@arm.com>
Reviewed-by: Dharmik Thakkar <dharmik.thakkar@arm.com>
Reviewed-by: Ruifeng Wang <ruifeng.wang@arm.com>
---
lib/librte_stack/rte_stack_lf_c11.h | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
Comments
> -----Original Message-----
> From: Steven Lariau <steven.lariau@arm.com>
> Sent: Friday, September 11, 2020 10:30 AM
> To: Eads, Gage <gage.eads@intel.com>; Olivier Matz <olivier.matz@6wind.com>
> Cc: dev@dpdk.org; nd@arm.com; dharmik.thakkar@arm.com; Steven Lariau
> <steven.lariau@arm.com>
> Subject: [PATCH 1/5] lib/stack: fix inconsistent weak / strong cas
>
> Fix cmpexchange usage of weak / strong.
> The generated code is the same on x86 and ARM (there is no weak
> cmpexchange), but the old usage was inconsistent.
> For push and pop update size, weak is used because cmpexchange is inside
> a loop.
> For pop update root, strong is used even though cmpexchange is inside a
> loop, because there may be a lot of operations to do in a loop iteration
> (locate the new head).
>
> Signed-off-by: Steven Lariau <steven.lariau@arm.com>
> Reviewed-by: Dharmik Thakkar <dharmik.thakkar@arm.com>
> Reviewed-by: Ruifeng Wang <ruifeng.wang@arm.com>
Acked-by: Gage Eads <gage.eads@intel.com>
Thanks,
Gage
@@ -96,7 +96,7 @@ __rte_stack_lf_pop_elems(struct rte_stack_lf_list *list,
/* len is updated on failure */
if (__atomic_compare_exchange_n(&list->len,
&len, len - num,
- 0, __ATOMIC_ACQUIRE,
+ 1, __ATOMIC_ACQUIRE,
__ATOMIC_ACQUIRE))
break;
}
@@ -149,7 +149,7 @@ __rte_stack_lf_pop_elems(struct rte_stack_lf_list *list,
(rte_int128_t *)&list->head,
(rte_int128_t *)&old_head,
(rte_int128_t *)&new_head,
- 1, __ATOMIC_RELEASE,
+ 0, __ATOMIC_RELEASE,
__ATOMIC_RELAXED);
} while (success == 0);