> Currently, we expect that only one callback can be active at any given
> moment, for a particular queue configuration, which is relatively easy
> to implement in a thread-safe way. However, we're about to add support
> for multiple queues per lcore, which will greatly increase the
> possibility of various race conditions.
>
> We could have used something like an RCU for this use case, but absent
> of a pressing need for thread safety we'll go the easy way and just
> mandate that the API's are to be called when all affected ports are
> stopped, and document this limitation. This greatly simplifies the
> `rte_power_monitor`-related code.
I think you need to update RN too with that.
Another thing - do you really need the whole port stopped?
>From what I understand - you work on queues, so it is enough for you
that related RX queue is stopped.
So, to make things a bit more robust, in pmgmt_queue_enable/disable
you can call rte_eth_rx_queue_info_get() and check queue state.
> Signed-off-by: Anatoly Burakov <anatoly.bura...@intel.com>
> ---
> lib/power/meson.build | 3 +
> lib/power/rte_power_pmd_mgmt.c | 106 ++++++++-------------------------
> lib/power/rte_power_pmd_mgmt.h | 6 ++
> 3 files changed, 35 insertions(+), 80 deletions(-)
>
> diff --git a/lib/power/meson.build b/lib/power/meson.build
> index c1097d32f1..4f6a242364 100644
> --- a/lib/power/meson.build
> +++ b/lib/power/meson.build
> @@ -21,4 +21,7 @@ headers = files(
> 'rte_power_pmd_mgmt.h',
> 'rte_power_guest_channel.h',
> )
> +if cc.has_argument('-Wno-cast-qual')
> + cflags += '-Wno-cast-qual'
> +endif
> deps += ['timer', 'ethdev']
> diff --git a/lib/power/rte_power_pmd_mgmt.c b/lib/power/rte_power_pmd_mgmt.c
> index db03cbf420..0707c60a4f 100644
> --- a/lib/power/rte_power_pmd_mgmt.c
> +++ b/lib/power/rte_power_pmd_mgmt.c
> @@ -40,8 +40,6 @@ struct pmd_queue_cfg {
> /**< Callback mode for this queue */
> const struct rte_eth_rxtx_callback *cur_cb;
> /**< Callback instance */
> - volatile bool umwait_in_progress;
> - /**< are we currently sleeping? */
> uint64_t empty_poll_stats;
> /**< Number of empty polls */
> } __rte_cache_aligned;
> @@ -92,30 +90,11 @@ clb_umwait(uint16_t port_id, uint16_t qidx, struct
> rte_mbuf **pkts __rte_unused,
> struct rte_power_monitor_cond pmc;
> uint16_t ret;
>
> - /*
> - * we might get a cancellation request while being
> - * inside the callback, in which case the wakeup
> - * wouldn't work because it would've arrived too early.
> - *
> - * to get around this, we notify the other thread that
> - * we're sleeping, so that it can spin until we're done.
> - * unsolicited wakeups are perfectly safe.
> - */
> - q_conf->umwait_in_progress = true;
> -
> - rte_atomic_thread_fence(__ATOMIC_SEQ_CST);
> -
> - /* check if we need to cancel sleep */
> - if (q_conf->pwr_mgmt_state == PMD_MGMT_ENABLED) {
> - /* use monitoring condition to sleep */
> - ret = rte_eth_get_monitor_addr(port_id, qidx,
> - &pmc);
> - if (ret == 0)
> - rte_power_monitor(&pmc, UINT64_MAX);
> - }
> - q_conf->umwait_in_progress = false;
> -
> - rte_atomic_thread_fence(__ATOMIC_SEQ_CST);
> + /* use monitoring condition to sleep */
> + ret = rte_eth_get_monitor_addr(port_id, qidx,
> + &pmc);
> + if (ret == 0)
> + rte_power_monitor(&pmc, UINT64_MAX);
> }
> } else
> q_conf->empty_poll_stats = 0;
> @@ -183,6 +162,7 @@ rte_power_ethdev_pmgmt_queue_enable(unsigned int
> lcore_id, uint16_t port_id,
> {
> struct pmd_queue_cfg *queue_cfg;
> struct rte_eth_dev_info info;
> + rte_rx_callback_fn clb;
> int ret;
>
> RTE_ETH_VALID_PORTID_OR_ERR_RET(port_id, -EINVAL);
> @@ -232,17 +212,7 @@ rte_power_ethdev_pmgmt_queue_enable(unsigned int
> lcore_id, uint16_t port_id,
> ret = -ENOTSUP;
> goto end;
> }
> - /* initialize data before enabling the callback */
> - queue_cfg->empty_poll_stats = 0;
> - queue_cfg->cb_mode = mode;
> - queue_cfg->umwait_in_progress = false;
> - queue_cfg->pwr_mgmt_state = PMD_MGMT_ENABLED;
> -
> - /* ensure we update our state before callback starts */
> - rte_atomic_thread_fence(__ATOMIC_SEQ_CST);
> -
> - queue_cfg->cur_cb = rte_eth_add_rx_callback(port_id, queue_id,
> - clb_umwait, NULL);
> + clb = clb_umwait;
> break;
> }
> case RTE_POWER_MGMT_TYPE_SCALE:
> @@ -269,16 +239,7 @@ rte_power_ethdev_pmgmt_queue_enable(unsigned int
> lcore_id, uint16_t port_id,
> ret = -ENOTSUP;
> goto end;
> }
> - /* initialize data before enabling the callback */
> - queue_cfg->empty_poll_stats = 0;
> - queue_cfg->cb_mode = mode;
> - queue_cfg->pwr_mgmt_state = PMD_MGMT_ENABLED;
> -
> - /* this is not necessary here, but do it anyway */
> - rte_atomic_thread_fence(__ATOMIC_SEQ_CST);
> -
> - queue_cfg->cur_cb = rte_eth_add_rx_callback(port_id,
> - queue_id, clb_scale_freq, NULL);
> + clb = clb_scale_freq;
> break;
> }
> case RTE_POWER_MGMT_TYPE_PAUSE:
> @@ -286,18 +247,21 @@ rte_power_ethdev_pmgmt_queue_enable(unsigned int
> lcore_id, uint16_t port_id,
> if (global_data.tsc_per_us == 0)
> calc_tsc();
>
> - /* initialize data before enabling the callback */
> - queue_cfg->empty_poll_stats = 0;
> - queue_cfg->cb_mode = mode;
> - queue_cfg->pwr_mgmt_state = PMD_MGMT_ENABLED;
> -
> - /* this is not necessary here, but do it anyway */
> - rte_atomic_thread_fence(__ATOMIC_SEQ_CST);
> -
> - queue_cfg->cur_cb = rte_eth_add_rx_callback(port_id, queue_id,
> - clb_pause, NULL);
> + clb = clb_pause;
> break;
> + default:
> + RTE_LOG(DEBUG, POWER, "Invalid power management type\n");
> + ret = -EINVAL;
> + goto end;
> }
> +
> + /* initialize data before enabling the callback */
> + queue_cfg->empty_poll_stats = 0;
> + queue_cfg->cb_mode = mode;
> + queue_cfg->pwr_mgmt_state = PMD_MGMT_ENABLED;
> + queue_cfg->cur_cb = rte_eth_add_rx_callback(port_id, queue_id,
> + clb, NULL);
> +
> ret = 0;
> end:
> return ret;
> @@ -323,27 +287,8 @@ rte_power_ethdev_pmgmt_queue_disable(unsigned int
> lcore_id,
> /* stop any callbacks from progressing */
> queue_cfg->pwr_mgmt_state = PMD_MGMT_DISABLED;
>
> - /* ensure we update our state before continuing */
> - rte_atomic_thread_fence(__ATOMIC_SEQ_CST);
> -
> switch (queue_cfg->cb_mode) {
> - case RTE_POWER_MGMT_TYPE_MONITOR:
> - {
> - bool exit = false;
> - do {
> - /*
> - * we may request cancellation while the other thread
> - * has just entered the callback but hasn't started
> - * sleeping yet, so keep waking it up until we know it's
> - * done sleeping.
> - */
> - if (queue_cfg->umwait_in_progress)
> - rte_power_monitor_wakeup(lcore_id);
> - else
> - exit = true;
> - } while (!exit);
> - }
> - /* fall-through */
> + case RTE_POWER_MGMT_TYPE_MONITOR: /* fall-through */
> case RTE_POWER_MGMT_TYPE_PAUSE:
> rte_eth_remove_rx_callback(port_id, queue_id,
> queue_cfg->cur_cb);
> @@ -356,10 +301,11 @@ rte_power_ethdev_pmgmt_queue_disable(unsigned int
> lcore_id,
> break;
> }
> /*
> - * we don't free the RX callback here because it is unsafe to do so
> - * unless we know for a fact that all data plane threads have stopped.
> + * the API doc mandates that the user stops all processing on affected
> + * ports before calling any of these API's, so we can assume that the
> + * callbacks can be freed. we're intentionally casting away const-ness.
> */
> - queue_cfg->cur_cb = NULL;
> + rte_free((void *)queue_cfg->cur_cb);
>
> return 0;
> }
> diff --git a/lib/power/rte_power_pmd_mgmt.h b/lib/power/rte_power_pmd_mgmt.h
> index 7a0ac24625..7557f5d7e1 100644
> --- a/lib/power/rte_power_pmd_mgmt.h
> +++ b/lib/power/rte_power_pmd_mgmt.h
> @@ -43,6 +43,9 @@ enum rte_power_pmd_mgmt_type {
> *
> * @note This function is not thread-safe.
> *
> + * @warning This function must be called when all affected Ethernet ports are
> + * stopped and no Rx/Tx is in progress!
> + *
> * @param lcore_id
> * The lcore the Rx queue will be polled from.
> * @param port_id
> @@ -69,6 +72,9 @@ rte_power_ethdev_pmgmt_queue_enable(unsigned int lcore_id,
> *
> * @note This function is not thread-safe.
> *
> + * @warning This function must be called when all affected Ethernet ports are
> + * stopped and no Rx/Tx is in progress!
> + *
> * @param lcore_id
> * The lcore the Rx queue is polled from.
> * @param port_id
> --
> 2.25.1
