On 5/23/2019 3:23 PM, 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>
Hi David, this change looks ok to me, tested a number scenarios and did not see any breakage. I'm happy to Ack, but will hold off applying until Ilya has a chance to look also as he's quite familiar with this area of the code base.
Ian
--- 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 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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