From mboxrd@z Thu Jan  1 00:00:00 1970
From: Olivier MATZ <olivier.matz-pdR9zngts4EAvxtiuMwx3w@public.gmane.org>
Subject: Re: [PATCH v4 07/17] eal: add rte_gettid() to acquire
 unique system tid
Date: Sun, 08 Feb 2015 21:00:31 +0100
Message-ID: <54D7C05F.9090501@6wind.com>
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To: Cunming Liang <cunming.liang-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>, dev-VfR2kkLFssw@public.gmane.org
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Hi,

On 02/02/2015 03:02 AM, Cunming Liang wrote:
> The rte_gettid() wraps the linux and freebsd syscall gettid().
> It provides a persistent unique thread id for the calling thread.
> It will save the unique id in TLS on the first time.
> 
> [...]
>
> +/**
> + * A wrap API for syscall gettid.
> + *
> + * @return
> + *   On success, returns the thread ID of calling process.
> + *   It always successful.
> + */
> +int rte_sys_gettid(void);
> +
> +/**
> + * Get system unique thread id.
> + *
> + * @return
> + *   On success, returns the thread ID of calling process.
> + *   It always successful.
> + */
> +static inline int rte_gettid(void)
> +{
> +	static RTE_DEFINE_PER_LCORE(int, _thread_id) = -1;
> +	if (RTE_PER_LCORE(_thread_id) == -1)
> +		RTE_PER_LCORE(_thread_id) = rte_sys_gettid();
> +	return RTE_PER_LCORE(_thread_id);
> +}

Instead of doing the test each time rte_gettid() is called, why not
having 2 functions:
  rte_init_tid() -> assign the per_lcore variable
  rte_gettid() -> return the per_lcore variable



Regards,
Olivier