From 4a6e683c4c69904214cce6de97b32d209ef95711 Mon Sep 17 00:00:00 2001 From: Honnappa Nagarahalli Date: Mon, 16 Jul 2018 23:52:44 -0500 Subject: [PATCH] ring: clarify preemptible nature of algorithm rte_ring implementation is not preemptible only under certain circumstances. This clarification is helpful for data plane and control plane communication using rte_ring. Signed-off-by: Honnappa Nagarahalli Reviewed-by: Gavin Hu Reviewed-by: Ola Liljedahl Acked-by: Olivier Matz --- doc/guides/prog_guide/env_abstraction_layer.rst | 12 ++++++++---- lib/librte_ring/rte_ring.h | 5 +++-- 2 files changed, 11 insertions(+), 6 deletions(-) diff --git a/doc/guides/prog_guide/env_abstraction_layer.rst b/doc/guides/prog_guide/env_abstraction_layer.rst index 4c51efd42c..d362c92090 100644 --- a/doc/guides/prog_guide/env_abstraction_layer.rst +++ b/doc/guides/prog_guide/env_abstraction_layer.rst @@ -449,13 +449,17 @@ Known Issues Bypassing this constraint may cause the 2nd pthread to spin until the 1st one is scheduled again. Moreover, if the 1st pthread is preempted by a context that has an higher priority, it may even cause a dead lock. - This does not mean it cannot be used, simply, there is a need to narrow down the situation when it is used by multi-pthread on the same core. + This means, use cases involving preemptible pthreads should consider using rte_ring carefully. - 1. It CAN be used for any single-producer or single-consumer situation. + 1. It CAN be used for preemptible single-producer and single-consumer use case. - 2. It MAY be used by multi-producer/consumer pthread whose scheduling policy are all SCHED_OTHER(cfs). User SHOULD be aware of the performance penalty before using it. + 2. It CAN be used for non-preemptible multi-producer and preemptible single-consumer use case. - 3. It MUST not be used by multi-producer/consumer pthreads, whose scheduling policies are SCHED_FIFO or SCHED_RR. + 3. It CAN be used for preemptible single-producer and non-preemptible multi-consumer use case. + + 4. It MAY be used by preemptible multi-producer and/or preemptible multi-consumer pthreads whose scheduling policy are all SCHED_OTHER(cfs), SCHED_IDLE or SCHED_BATCH. User SHOULD be aware of the performance penalty before using it. + + 5. It MUST not be used by multi-producer/consumer pthreads, whose scheduling policies are SCHED_FIFO or SCHED_RR. + rte_timer diff --git a/lib/librte_ring/rte_ring.h b/lib/librte_ring/rte_ring.h index de1a5f366b..7a731d070d 100644 --- a/lib/librte_ring/rte_ring.h +++ b/lib/librte_ring/rte_ring.h @@ -26,8 +26,9 @@ * - Bulk dequeue. * - Bulk enqueue. * - * Note: the ring implementation is not preemptable. A lcore must not - * be interrupted by another task that uses the same ring. + * Note: the ring implementation is not preemptible. Refer to Programmer's + * guide/Environment Abstraction Layer/Multiple pthread/Known Issues/rte_ring + * for more information. * */ -- 2.20.1