Re: [PATCH v2 1/3] eal: add rte control thread create API

["Mattias Rönnblom" <hofors@lysator.liu.se>]

On 2022-12-06 18:28, Tyler Retzlaff wrote:
> Add rte_control_thread_create API as a replacement for
> rte_ctrl_thread_create to allow deprecation of the use of platform
> specific types in DPDK public API.
> 
> Signed-off-by: Tyler Retzlaff <roretzla@linux.microsoft.com>
> ---
>   lib/eal/common/eal_common_thread.c | 93 ++++++++++++++++++++++++++++++++++----
>   lib/eal/include/rte_thread.h       | 29 ++++++++++++
>   lib/eal/version.map                |  3 ++
>   3 files changed, 117 insertions(+), 8 deletions(-)
> 
> diff --git a/lib/eal/common/eal_common_thread.c b/lib/eal/common/eal_common_thread.c
> index c5d8b43..7950b50 100644
> --- a/lib/eal/common/eal_common_thread.c
> +++ b/lib/eal/common/eal_common_thread.c
> @@ -234,7 +234,10 @@ enum __rte_ctrl_thread_status {
>   };
>   
>   struct rte_thread_ctrl_params {
> -	void *(*start_routine)(void *);
> +	union {
> +		void *(*start_routine)(void *);
> +		rte_thread_func thread_func;

To be consistent with function naming scheme, where "ctrl" is the old 
API, and "control" the new, you could call the start functions something 
with "ctrl" and "control" as well.

Maybe it's worth mentioning that fact somewhere in the beginning of the 
file, as a comment (i.e., that "ctrl" denotes the old API).

> +	} u;
>   	void *arg;
>   	int ret;

Why is 'ret' needed? (This question is unrelated to your patch.)

>   	/* Control thread status.
> @@ -243,14 +246,12 @@ struct rte_thread_ctrl_params {
>   	enum __rte_ctrl_thread_status ctrl_thread_status;
>   };
>   
> -static void *ctrl_thread_init(void *arg)
> +static int ctrl_thread_init(void *arg)
>   {
>   	struct internal_config *internal_conf =
>   		eal_get_internal_configuration();
>   	rte_cpuset_t *cpuset = &internal_conf->ctrl_cpuset;
>   	struct rte_thread_ctrl_params *params = arg;
> -	void *(*start_routine)(void *) = params->start_routine;
> -	void *routine_arg = params->arg;
>   
>   	__rte_thread_init(rte_lcore_id(), cpuset);
>   	params->ret = pthread_setaffinity_np(pthread_self(), sizeof(*cpuset),
> @@ -258,13 +259,35 @@ static void *ctrl_thread_init(void *arg)
>   	if (params->ret != 0) {
>   		__atomic_store_n(&params->ctrl_thread_status,
>   			CTRL_THREAD_ERROR, __ATOMIC_RELEASE);
> -		return NULL;
> +		return params->ret;
>   	}
>   
>   	__atomic_store_n(&params->ctrl_thread_status,
>   		CTRL_THREAD_RUNNING, __ATOMIC_RELEASE);
>   
> -	return start_routine(routine_arg);
> +	return 0;
> +}
> +
> +static void *ctrl_thread_start(void *arg)
> +{
> +	struct rte_thread_ctrl_params *params = arg;
> +	void *(*start_routine)(void *) = params->u.start_routine;
> +
> +	if (ctrl_thread_init(arg) != 0)
> +		return NULL;
> +
> +	return start_routine(params->arg);
> +}
> +
> +static uint32_t control_thread_start(void *arg)
> +{
> +	struct rte_thread_ctrl_params *params = arg;
> +	rte_thread_func start_routine = params->u.thread_func;
> +
> +	if (ctrl_thread_init(arg) != 0)
> +		return params->ret;
> +
> +	return start_routine(params->arg);
>   }
>   
>   int
> @@ -280,12 +303,12 @@ static void *ctrl_thread_init(void *arg)
>   	if (!params)
>   		return -ENOMEM;
>   
> -	params->start_routine = start_routine;
> +	params->u.start_routine = start_routine;
>   	params->arg = arg;
>   	params->ret = 0;
>   	params->ctrl_thread_status = CTRL_THREAD_LAUNCHING;
>   
> -	ret = pthread_create(thread, attr, ctrl_thread_init, (void *)params);
> +	ret = pthread_create(thread, attr, ctrl_thread_start, (void *)params);
>   	if (ret != 0) {
>   		free(params);
>   		return -ret;
> @@ -322,6 +345,60 @@ static void *ctrl_thread_init(void *arg)
>   }
>   
>   int
> +rte_control_thread_create(rte_thread_t *thread, const char *name,
> +	const rte_thread_attr_t *attr,
> +	rte_thread_func start_routine, void *arg)
> +{
> +	struct rte_thread_ctrl_params *params;
> +	enum __rte_ctrl_thread_status ctrl_thread_status;
> +	int ret;
> +
> +	params = malloc(sizeof(*params));
> +	if (!params)

params == NULL

> +		return -ENOMEM;
> +
> +	params->u.thread_func = start_routine;
> +	params->arg = arg;
> +	params->ret = 0;
> +	params->ctrl_thread_status = CTRL_THREAD_LAUNCHING;
> +
> +	ret = rte_thread_create(thread, attr, control_thread_start, params);
> +	if (ret != 0) {
> +		free(params);
> +		return -ret;
> +	}
> +
> +	if (name != NULL) {
> +		ret = rte_thread_setname((pthread_t)thread->opaque_id, name);
> +		if (ret < 0)
> +			RTE_LOG(DEBUG, EAL,
> +				"Cannot set name for ctrl thread\n");
> +	}
> +
> +	/* Wait for the control thread to initialize successfully */
> +	while ((ctrl_thread_status =
> +			__atomic_load_n(&params->ctrl_thread_status,
> +			__ATOMIC_ACQUIRE)) == CTRL_THREAD_LAUNCHING) {
> +		/* Yield the CPU. Using sched_yield call requires maintaining
> +		 * another implementation for Windows as sched_yield is not
> +		 * supported on Windows.
> +		 */

sched_yield() also doesn't necessarily yield the CPU.

> +		rte_delay_us_sleep(1);
> +	}
> +
> +	/* Check if the control thread encountered an error */
> +	if (ctrl_thread_status == CTRL_THREAD_ERROR) {
> +		/* ctrl thread is exiting */
> +		rte_thread_join(*thread, NULL);
> +	}
> +
> +	ret = params->ret;
> +	free(params);
> +
> +	return ret;
> +}
> +
> +int
>   rte_thread_register(void)
>   {
>   	unsigned int lcore_id;
> diff --git a/lib/eal/include/rte_thread.h b/lib/eal/include/rte_thread.h
> index b9edf70..ae7afbe 100644
> --- a/lib/eal/include/rte_thread.h
> +++ b/lib/eal/include/rte_thread.h
> @@ -95,6 +95,35 @@ int rte_thread_create(rte_thread_t *thread_id,
>   		rte_thread_func thread_func, void *arg);
>   
>   /**
> + * Create a control thread.
> + *
> + * Creates a control thread with the given name and attributes. The
> + * affinity of the new thread is based on the CPU affinity retrieved
> + * at the time rte_eal_init() was called, the dataplane and service
> + * lcores are then excluded. If setting the name of the thread fails,

"the EAL threads are then excluded"

> + * the error is ignored and a debug message is logged.
> + *
> + * @param thread
> + *   Filled with the thread id of the new created thread.
> + * @param name
> + *   The name of the control thread (max 16 characters including '\0').

Is there a constant for this limit?

> + * @param thread_attr
> + *   Attributes for the new thread.
> + * @param thread_func
> + *   Function to be executed by the new thread.
> + * @param arg
> + *   Argument passed to start_routine.
> + * @return
> + *   On success, returns 0; on error, it returns a negative value
> + *   corresponding to the error number.

List the possible error codes.

> + */
> +__rte_experimental
> +int
> +rte_control_thread_create(rte_thread_t *thread, const char *name,
> +		const rte_thread_attr_t *thread_attr,
> +		rte_thread_func thread_func, void *arg);
> +
> +/**
>    * @warning
>    * @b EXPERIMENTAL: this API may change without prior notice.
>    *
> diff --git a/lib/eal/version.map b/lib/eal/version.map
> index 7ad12a7..8f9eeb9 100644
> --- a/lib/eal/version.map
> +++ b/lib/eal/version.map
> @@ -440,6 +440,9 @@ EXPERIMENTAL {
>   	rte_thread_detach;
>   	rte_thread_equal;
>   	rte_thread_join;
> +
> +	# added in 23.03
> +	rte_control_thread_create;
>   };
>   
>   INTERNAL {