[dpdk-dev] [PATCH v4 17/17] timer: add support to non-EAL thread

Olivier MATZ olivier.matz at 6wind.com
Tue Feb 10 18:45:16 CET 2015


Hi,

On 02/02/2015 03:02 AM, Cunming Liang wrote:
> Allow to setup timers only for EAL (lcore) threads (__lcore_id < MAX_LCORE_ID).
> E.g. – dynamically created thread will be able to reset/stop timer for lcore thread,
> but it will be not allowed to setup timer for itself or another non-lcore thread.
> rte_timer_manage() for non-lcore thread would simply do nothing and return straightway.
>
> Signed-off-by: Cunming Liang <cunming.liang at intel.com>
> ---
>   lib/librte_timer/rte_timer.c | 40 +++++++++++++++++++++++++++++++---------
>   lib/librte_timer/rte_timer.h |  2 +-
>   2 files changed, 32 insertions(+), 10 deletions(-)
>
> diff --git a/lib/librte_timer/rte_timer.c b/lib/librte_timer/rte_timer.c
> index 269a992..601c159 100644
> --- a/lib/librte_timer/rte_timer.c
> +++ b/lib/librte_timer/rte_timer.c
> @@ -79,9 +79,10 @@ static struct priv_timer priv_timer[RTE_MAX_LCORE];
>
>   /* when debug is enabled, store some statistics */
>   #ifdef RTE_LIBRTE_TIMER_DEBUG
> -#define __TIMER_STAT_ADD(name, n) do {				\
> -		unsigned __lcore_id = rte_lcore_id();		\
> -		priv_timer[__lcore_id].stats.name += (n);	\
> +#define __TIMER_STAT_ADD(name, n) do {					\
> +		unsigned __lcore_id = rte_lcore_id();			\
> +		if (__lcore_id < RTE_MAX_LCORE)				\
> +			priv_timer[__lcore_id].stats.name += (n);	\
>   	} while(0)
>   #else
>   #define __TIMER_STAT_ADD(name, n) do {} while(0)
> @@ -127,15 +128,26 @@ timer_set_config_state(struct rte_timer *tim,
>   	unsigned lcore_id;
>
>   	lcore_id = rte_lcore_id();
> +	if (lcore_id >= RTE_MAX_LCORE)
> +		lcore_id = LCORE_ID_ANY;

Is this still valid?
In my understanding, rte_lcore_id() was returning the core id or
LCORE_ID_ANY if it's a non-EAL thread.

>
>   	/* wait that the timer is in correct status before update,
>   	 * and mark it as being configured */
>   	while (success == 0) {
>   		prev_status.u32 = tim->status.u32;
>
> +		/*
> +		 * prevent race condition of non-EAL threads
> +		 * to update the timer. When 'owner == LCORE_ID_ANY',
> +		 * it means updated by a non-EAL thread.
> +		 */
> +		if (lcore_id == (unsigned)LCORE_ID_ANY &&
> +		    (uint16_t)lcore_id == prev_status.owner)
> +			return -1;
> +

Are you sure this is required?

I think prev_status.owner can be LCORE_ID_ANY only in config state,
as a timer cannot be scheduled on a non-EAL thread. And there is
already a test that returns -1 if state is CONFIG.


>   		/* timer is running on another core, exit */
>   		if (prev_status.state == RTE_TIMER_RUNNING &&
> -		    (unsigned)prev_status.owner != lcore_id)
> +		    prev_status.owner != (uint16_t)lcore_id)
>   			return -1;
>
>   		/* timer is being configured on another core */
> @@ -366,9 +378,13 @@ __rte_timer_reset(struct rte_timer *tim, uint64_t expire,
>
>   	/* round robin for tim_lcore */
>   	if (tim_lcore == (unsigned)LCORE_ID_ANY) {
> -		tim_lcore = rte_get_next_lcore(priv_timer[lcore_id].prev_lcore,
> -					       0, 1);
> -		priv_timer[lcore_id].prev_lcore = tim_lcore;
> +		if (lcore_id < RTE_MAX_LCORE) {

if (lcore_id != LCORE_ID_ANY) ?


> +			tim_lcore = rte_get_next_lcore(
> +				priv_timer[lcore_id].prev_lcore,
> +				0, 1);
> +			priv_timer[lcore_id].prev_lcore = tim_lcore;
> +		} else
> +			tim_lcore = rte_get_next_lcore(LCORE_ID_ANY, 0, 1);

I think the following line:
tim_lcore = rte_get_next_lcore(LCORE_ID_ANY, 0, 1);
Will return the first enabled core.

Maybe using rte_get_master_lcore() is clearer?



>   	}
>
>   	/* wait that the timer is in correct status before update,
> @@ -378,7 +394,8 @@ __rte_timer_reset(struct rte_timer *tim, uint64_t expire,
>   		return -1;
>
>   	__TIMER_STAT_ADD(reset, 1);
> -	if (prev_status.state == RTE_TIMER_RUNNING) {
> +	if (prev_status.state == RTE_TIMER_RUNNING &&
> +	    lcore_id < RTE_MAX_LCORE) {

if (lcore_id != LCORE_ID_ANY) ?


>   		priv_timer[lcore_id].updated = 1;
>   	}
>
> @@ -455,7 +472,8 @@ rte_timer_stop(struct rte_timer *tim)
>   		return -1;
>
>   	__TIMER_STAT_ADD(stop, 1);
> -	if (prev_status.state == RTE_TIMER_RUNNING) {
> +	if (prev_status.state == RTE_TIMER_RUNNING &&
> +	    lcore_id < RTE_MAX_LCORE) {

if (lcore_id != LCORE_ID_ANY) ?


>   		priv_timer[lcore_id].updated = 1;
>   	}
>
> @@ -499,6 +517,10 @@ void rte_timer_manage(void)
>   	uint64_t cur_time;
>   	int i, ret;
>
> +	/* timer manager only runs on EAL thread */
> +	if (lcore_id >= RTE_MAX_LCORE)
> +		return;
> +

Maybe an assert is more visible here. Else, if someone calls
rte_timer_manage() from a non-EAL core, it will just exit
silently.

Maybe adding a comment in rte_timer.h saying that this function
must be called from an EAL core would also help.



Regards,
Olivier



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