On 23.05.2019 17:23, David Marchand wrote:
> No need for a latch here since we don't have to wait.
> A simple boolean flag is enough.
>
> The memory order on the reload flag is changed to rel-acq ordering to
> serve as a synchronisation point between the pmd threads and the control
> thread that asks for termination.
>
> Fixes: e4cfed38b159 ("dpif-netdev: Add poll-mode-device thread.")
> Signed-off-by: David Marchand <david.march...@redhat.com>
> Acked-by: Eelco Chaudron <echau...@redhat.com>
> ---
> lib/dpif-netdev.c | 14 ++++++--------
> 1 file changed, 6 insertions(+), 8 deletions(-)
>
> ---
> Changelog since RFC v2:
> - removed now unused latch.h inclusion
>
> Changelog since RFC v1:
> - added memory ordering on 'reload' atomic to serve as a synchronisation
> point between control thread and pmd threads
>
Acked-by: Ilya Maximets <i.maxim...@samsung.com>
> diff --git a/lib/dpif-netdev.c b/lib/dpif-netdev.c
> index 5a6f2ab..19d7f7d 100644
> --- a/lib/dpif-netdev.c
> +++ b/lib/dpif-netdev.c
> @@ -48,7 +48,6 @@
> #include "hmapx.h"
> #include "id-pool.h"
> #include "ipf.h"
> -#include "latch.h"
> #include "netdev.h"
> #include "netdev-provider.h"
> #include "netdev-vport.h"
> @@ -681,10 +680,10 @@ struct dp_netdev_pmd_thread {
> /* Current context of the PMD thread. */
> struct dp_netdev_pmd_thread_ctx ctx;
>
> - struct latch exit_latch; /* For terminating the pmd thread. */
> struct seq *reload_seq;
> uint64_t last_reload_seq;
> atomic_bool reload; /* Do we need to reload ports? */
> + atomic_bool exit; /* For terminating the pmd thread. */
> pthread_t thread;
> unsigned core_id; /* CPU core id of this pmd thread. */
> int numa_id; /* numa node id of this pmd thread. */
> @@ -1756,7 +1755,7 @@ dp_netdev_reload_pmd__(struct dp_netdev_pmd_thread *pmd)
>
> ovs_mutex_lock(&pmd->cond_mutex);
> seq_change(pmd->reload_seq);
> - atomic_store_relaxed(&pmd->reload, true);
> + atomic_store_explicit(&pmd->reload, true, memory_order_release);
> ovs_mutex_cond_wait(&pmd->cond, &pmd->cond_mutex);
> ovs_mutex_unlock(&pmd->cond_mutex);
> }
> @@ -5468,7 +5467,7 @@ reload:
> emc_cache_slow_sweep(&((pmd->flow_cache).emc_cache));
> }
>
> - atomic_read_relaxed(&pmd->reload, &reload);
> + atomic_read_explicit(&pmd->reload, &reload,
> memory_order_acquire);
> if (reload) {
> break;
> }
> @@ -5479,7 +5478,7 @@ reload:
> ovs_mutex_unlock(&pmd->perf_stats.stats_mutex);
>
> poll_cnt = pmd_load_queues_and_ports(pmd, &poll_list);
> - exiting = latch_is_set(&pmd->exit_latch);
> + atomic_read_relaxed(&pmd->exit, &exiting);
> /* Signal here to make sure the pmd finishes
> * reloading the updated configuration. */
> dp_netdev_pmd_reload_done(pmd);
> @@ -5898,7 +5897,7 @@ dp_netdev_configure_pmd(struct dp_netdev_pmd_thread
> *pmd, struct dp_netdev *dp,
> pmd->n_output_batches = 0;
>
> ovs_refcount_init(&pmd->ref_cnt);
> - latch_init(&pmd->exit_latch);
> + atomic_init(&pmd->exit, false);
> pmd->reload_seq = seq_create();
> pmd->last_reload_seq = seq_read(pmd->reload_seq);
> atomic_init(&pmd->reload, false);
> @@ -5945,7 +5944,6 @@ dp_netdev_destroy_pmd(struct dp_netdev_pmd_thread *pmd)
> cmap_destroy(&pmd->classifiers);
> cmap_destroy(&pmd->flow_table);
> ovs_mutex_destroy(&pmd->flow_mutex);
> - latch_destroy(&pmd->exit_latch);
> seq_destroy(pmd->reload_seq);
> xpthread_cond_destroy(&pmd->cond);
> ovs_mutex_destroy(&pmd->cond_mutex);
> @@ -5967,7 +5965,7 @@ dp_netdev_del_pmd(struct dp_netdev *dp, struct
> dp_netdev_pmd_thread *pmd)
> pmd_free_static_tx_qid(pmd);
> ovs_mutex_unlock(&dp->non_pmd_mutex);
> } else {
> - latch_set(&pmd->exit_latch);
> + atomic_store_relaxed(&pmd->exit, true);
> dp_netdev_reload_pmd__(pmd);
> xpthread_join(pmd->thread, NULL);
> }
>
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