From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from dpdk.org (dpdk.org [92.243.14.124]) by inbox.dpdk.org (Postfix) with ESMTP id 51453A04B2; Sat, 2 May 2020 02:03:12 +0200 (CEST) Received: from [92.243.14.124] (localhost [127.0.0.1]) by dpdk.org (Postfix) with ESMTP id B13F81D9A2; Sat, 2 May 2020 02:03:05 +0200 (CEST) Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by dpdk.org (Postfix) with ESMTP id A67ED1D999; Sat, 2 May 2020 02:03:03 +0200 (CEST) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id DAF641063; Fri, 1 May 2020 17:03:02 -0700 (PDT) Received: from qc2400f-1.austin.arm.com (qc2400f-1.austin.arm.com [10.118.14.48]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id C67C73F305; Fri, 1 May 2020 17:03:02 -0700 (PDT) From: Honnappa Nagarahalli To: dev@dpdk.org, phil.yang@arm.com, harry.van.haaren@intel.com Cc: thomas@monjalon.net, david.marchand@redhat.com, konstantin.ananyev@intel.com, jerinj@marvell.com, hemant.agrawal@nxp.com, gage.eads@intel.com, bruce.richardson@intel.com, honnappa.nagarahalli@arm.com, nd@arm.com, stable@dpdk.org Date: Fri, 1 May 2020 19:02:40 -0500 Message-Id: <20200502000245.11071-2-honnappa.nagarahalli@arm.com> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20200502000245.11071-1-honnappa.nagarahalli@arm.com> References: <1587659482-27133-1-git-send-email-phil.yang@arm.com> <20200502000245.11071-1-honnappa.nagarahalli@arm.com> Subject: [dpdk-dev] [PATCH v3 1/6] service: fix race condition for MT unsafe service X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Sender: "dev" The MT unsafe service might get configured to run on another core while the service is running currently. This might result in the MT unsafe service running on multiple cores simultaneously. Use 'execute_lock' always when the service is MT unsafe. If the service is known to be mmapped on a single lcore, setting the service capability to MT safe will avoid taking the lock and improve the performance. Fixes: e9139a32f6e8 ("service: add function to run on app lcore") Cc: stable@dpdk.org Signed-off-by: Honnappa Nagarahalli Reviewed-by: Phil Yang --- lib/librte_eal/common/rte_service.c | 11 +++++------ lib/librte_eal/include/rte_service.h | 8 ++++++-- lib/librte_eal/include/rte_service_component.h | 6 +++++- 3 files changed, 16 insertions(+), 9 deletions(-) diff --git a/lib/librte_eal/common/rte_service.c b/lib/librte_eal/common/rte_service.c index 70d17a5d7..b8c465eb9 100644 --- a/lib/librte_eal/common/rte_service.c +++ b/lib/librte_eal/common/rte_service.c @@ -50,6 +50,10 @@ struct rte_service_spec_impl { uint8_t internal_flags; /* per service statistics */ + /* Indicates how many cores the service is mapped to run on. + * It does not indicate the number of cores the service is running + * on currently. + */ rte_atomic32_t num_mapped_cores; uint64_t calls; uint64_t cycles_spent; @@ -370,12 +374,7 @@ service_run(uint32_t i, struct core_state *cs, uint64_t service_mask, cs->service_active_on_lcore[i] = 1; - /* check do we need cmpset, if MT safe or <= 1 core - * mapped, atomic ops are not required. - */ - const int use_atomics = (service_mt_safe(s) == 0) && - (rte_atomic32_read(&s->num_mapped_cores) > 1); - if (use_atomics) { + if (service_mt_safe(s) == 0) { if (!rte_atomic32_cmpset((uint32_t *)&s->execute_lock, 0, 1)) return -EBUSY; diff --git a/lib/librte_eal/include/rte_service.h b/lib/librte_eal/include/rte_service.h index d8701dd4c..3a1c735c5 100644 --- a/lib/librte_eal/include/rte_service.h +++ b/lib/librte_eal/include/rte_service.h @@ -104,12 +104,16 @@ int32_t rte_service_probe_capability(uint32_t id, uint32_t capability); * Each core can be added or removed from running a specific service. This * function enables or disables *lcore* to run *service_id*. * - * If multiple cores are enabled on a service, an atomic is used to ensure that - * only one cores runs the service at a time. The exception to this is when + * If multiple cores are enabled on a service, a lock is used to ensure that + * only one core runs the service at a time. The exception to this is when * a service indicates that it is multi-thread safe by setting the capability * called RTE_SERVICE_CAP_MT_SAFE. With the multi-thread safe capability set, * the service function can be run on multiple threads at the same time. * + * If the service is known to be mapped to a single lcore, setting the + * capability of the service to RTE_SERVICE_CAP_MT_SAFE can achieve + * better performance by avoiding the use of lock. + * * @param service_id the service to apply the lcore to * @param lcore The lcore that will be mapped to service * @param enable Zero to unmap or disable the core, non-zero to enable diff --git a/lib/librte_eal/include/rte_service_component.h b/lib/librte_eal/include/rte_service_component.h index 16eab79ee..b75aba11b 100644 --- a/lib/librte_eal/include/rte_service_component.h +++ b/lib/librte_eal/include/rte_service_component.h @@ -43,7 +43,7 @@ struct rte_service_spec { /** * Register a new service. * - * A service represents a component that the requires CPU time periodically to + * A service represents a component that requires CPU time periodically to * achieve its purpose. * * For example the eventdev SW PMD requires CPU cycles to perform its @@ -56,6 +56,10 @@ struct rte_service_spec { * *rte_service_component_runstate_set*, which indicates that the service * component is ready to be executed. * + * If the service is known to be mapped to a single lcore, setting the + * capability of the service to RTE_SERVICE_CAP_MT_SAFE can achieve + * better performance. + * * @param spec The specification of the service to register * @param[out] service_id A pointer to a uint32_t, which will be filled in * during registration of the service. It is set to the integers -- 2.17.1