[dpdk-dev] [RFC] eal: make rte_rand() MT safe

[Mattias Rönnblom]

On 2019-04-05 16:28, Bruce Richardson wrote:
> On Fri, Apr 05, 2019 at 03:51:39PM +0200, Mattias Rönnblom wrote:
>> On 2019-04-05 15:45, Mattias Rönnblom wrote:
>>> The rte_rand() documentation left it unspecified if the rte_rand() was
>>> multi-thread safe or not, and the implementation (based on lrand48())
>>> was not.
>>>
>>> This commit makes rte_rand() safe to use from any lcore thread by
>>> using lrand48_r() and per-lcore random state structs. Besides the
>>> obvious improvement in terms of correctness (for concurrent users),
>>> this also much improves rte_rand() performance, since the threads no
>>> longer shares state. For the single-threaded case, this patch causes
>>> ~10% rte_rand() performance degradation.
>>>
>>
>> It's a little unclear to me, if lrand48_r() exists in FreeBSD or not. Could
>> someone confirm?
>>
> Nothing shows up for me in the man pages for such a function on FreeBSD 12,
> so I suspect they aren't available.
>   

Could arc4random(3) be a good replacement on FreeBSD? It "can be called 
in almost all coding environments, including pthreads(3)" according to 
the man page, so assume it's MT safe.