[PATCH v9] eal: add seqlock

[Mattias Rönnblom]

On 2022-06-01 00:45, Stephen Hemminger wrote:
> On Mon, 23 May 2022 16:23:46 +0200
> Mattias Rönnblom <mattias.ronnblom at ericsson.com> wrote:
> 
>> +/**
>> + * The RTE seqcount type.
>> + */
>> +typedef struct {
>> +	uint32_t sn; /**< A sequence number for the protected data. */
>> +} rte_seqcount_t;
> 
> Don't need structure for only one element.
> 

The struct adds a degree of type safety, with no run-time cost.

> typedef uint32_t rte_seqcount_t;
> 
> +	if (unlikely(begin_sn != end_sn))
> +		return true;
> +
> +	return false;
> 
> Prefer to avoid conditional if possible (compiler will optimize it as):
> 
>          return begin_sn == end_sn;

Is this a readability argument, or a performance one?

The compiler might use the unlikely hint to do something useful, like 
avoiding a branch in the common case.