From mboxrd@z Thu Jan 1 00:00:00 1970 From: Thomas Monjalon Subject: Re: [PATCH v2] service: fix race in service on app lcore function Date: Tue, 07 Nov 2017 01:26:42 +0100 Message-ID: <3101300.eJ1rulUoFZ@xps> References: <1509450542-123626-1-git-send-email-harry.van.haaren@intel.com> <1509562081-52763-1-git-send-email-harry.van.haaren@intel.com> <20171102094105.GB19712@bricha3-MOBL3.ger.corp.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7Bit Cc: dev@dpdk.org, Bruce Richardson , pbhagavatula@caviumnetworks.com To: Harry van Haaren Return-path: Received: from out4-smtp.messagingengine.com (out4-smtp.messagingengine.com [66.111.4.28]) by dpdk.org (Postfix) with ESMTP id 69EE21B33E for ; Tue, 7 Nov 2017 01:26:43 +0100 (CET) In-Reply-To: <20171102094105.GB19712@bricha3-MOBL3.ger.corp.intel.com> List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Sender: "dev" 02/11/2017 10:41, Bruce Richardson: > On Wed, Nov 01, 2017 at 06:48:01PM +0000, Harry van Haaren wrote: > > This commit fixes a possible race condition if an application > > uses the service-cores infrastructure and the function to run > > a service on an application lcore at the same time. > > > > The fix is to change the num_mapped_cores variable to be an > > atomic variable. This causes concurrent accesses by multiple > > threads to a service using rte_service_run_iter_on_app_lcore() > > to detect if another core is currently mapped to the service, > > and refuses to run if it is not multi-thread safe. > > > > The run iteration on app lcore function has two arguments, the > > service id to run, and if atomics should be used to serialize access > > to multi-thread unsafe services. This allows applications to choose > > if they wish to use use the service-cores feature, or if they > > take responsibility themselves for serializing invoking a service. > > See doxygen documentation for more details. > > > > Two unit tests were added to verify the behaviour of the > > function to run a service on an application core, testing both > > a multi-thread safe service, and a multi-thread unsafe service. > > > > The doxygen API documentation for the function has been updated > > to reflect the current and correct behaviour. > > > > Fixes: e9139a32f6e8 ("service: add function to run on app lcore") > > > > Signed-off-by: Harry van Haaren > > > > --- > > > > v2: > > - Rework function to have parameter that allows the application > > to select if it requires atomics to be used of it the application > > wishes to take responsibility for serializing instead. > > > This approach seems better to me. I think the function itself might be > better if you just duplicated a bit more code to reduce the number of > checks on the serialization variable, but it's readable enough as it is > now, so > > Acked-by: Bruce Richardson Applied, thanks