Re: [dpdk-stable] [dpdk-dev] [PATCH 1/1] timer: add limitation note for sync stop and reset

[Honnappa Nagarahalli <Honnappa.Nagarahalli@arm.com>]

<snip>

> 
> If a timer's callback function calls rte_timer_reset_sync() or
> rte_timer_stop_sync() on another timer that is in the RUNNING state and
> owned by the current lcore, the *_sync() calls will loop indefinitely.
> 
> Relatedly, if a timer's callback function calls *_sync() on another timer that is
> in the RUNNING state and is owned by a different lcore, but a timer callback
> function runs on that different lcore and calls
> *_sync() on a timer that is in the RUNNING state and owned by the current
> lcore, the two lcores will loop indefinitely.
> 
> Add a note in the rte_timer_stop_sync and rte_timer_reset_sync
> documentation that indicates that these APIs should not be used inside
> timer callback functions in order to avoid the hangs described above, and
> suggests an alternative.
> 
> Bugzilla ID: 491
> Cc: stable@dpdk.org
> 
> Signed-off-by: Erik Gabriel Carrillo <erik.g.carrillo@intel.com>
Looks good.
Reviewed-by: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>

> ---
>  lib/librte_timer/rte_timer.h | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 
> diff --git a/lib/librte_timer/rte_timer.h b/lib/librte_timer/rte_timer.h index
> c6b3d45..d7c3e03 100644
> --- a/lib/librte_timer/rte_timer.h
> +++ b/lib/librte_timer/rte_timer.h
> @@ -274,6 +274,12 @@ int rte_timer_reset(struct rte_timer *tim, uint64_t
> ticks,
>   *   The callback function of the timer.
>   * @param arg
>   *   The user argument of the callback function.
> + *
> + * @note
> + *   This API should not be called inside a timer's callback function to
> + *   reset another timer; doing so could hang in certain scenarios. Instead,
> + *   the rte_timer_reset() API can be called directly and its return code
> + *   can be checked for success or failure.
>   */
>  void
>  rte_timer_reset_sync(struct rte_timer *tim, uint64_t ticks, @@ -313,6
> +319,12 @@ int rte_timer_stop(struct rte_timer *tim);
>   *
>   * @param tim
>   *   The timer handle.
> + *
> + * @note
> + *   This API should not be called inside a timer's callback function to
> + *   stop another timer; doing so could hang in certain scenarios. Instead,
> the
> + *   rte_timer_stop() API can be called directly and its return code can
> + *   be checked for success or failure.
>   */
>  void rte_timer_stop_sync(struct rte_timer *tim);
> 
> --
> 2.6.4