[PATCH v5] eal: add seqlock

[fengchengwen]

On 2022/5/6 9:33, Honnappa Nagarahalli wrote:
> <snip>
> 
>>> +__rte_experimental
>>> +static inline bool
>>> +rte_seqlock_read_retry(const rte_seqlock_t *seqlock, uint32_t
>>> +begin_sn) {
>>> +	uint32_t end_sn;
>>> +
>>> +	/* An odd sequence number means the protected data was being
>>> +	 * modified already at the point of the rte_seqlock_read_begin()
>>> +	 * call.
>>> +	 */
>>> +	if (unlikely(begin_sn & 1))
>>> +		return true;
>>> +
>>> +	/* make sure the data loads happens before the sn load */
>>> +	rte_atomic_thread_fence(__ATOMIC_ACQUIRE);
>>
>> In ARMv8, the rte_atomic_thread_fence(__ATOMIC_ACQUIRE) and
>> rte_smp_rmb() both output 'dma ishld'
>> Suggest use rte_smp_rmb(), please see below comment.
> rte_smp_xxx APIs are deprecated. Please check [1]
> 
> [1] https://www.dpdk.org/blog/2021/03/26/dpdk-adopts-the-c11-memory-model/

Got it, thanks

And I have a question about ARM: why can't find the parameter(rte_atomic_thread_fence(?)) corresponding to 'dmb ishst'?
I tried __ATOMIC_RELEASE/ACQ_REL/SEQ_CST and can't find it.

> 
> <snip>
>