From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Burakov, Anatoly" Subject: Re: [PATCH] eal: initialize alarms early Date: Thu, 28 Mar 2019 13:14:37 +0000 Message-ID: References: <20190326184331.13850-1-dariusz.stojaczyk@intel.com> <1752426.1oQredii45@xps> <20190328104313.GA1418@bricha3-MOBL.ger.corp.intel.com> <2018712.ubzJDVHxhL@xps> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Cc: "Stojaczyk, Dariusz" , "dev@dpdk.org" , "Zhang, Qi Z" , "stable@dpdk.org" To: Thomas Monjalon , Bruce Richardson Return-path: In-Reply-To: <2018712.ubzJDVHxhL@xps> Content-Language: en-US List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Sender: "dev" On 28-Mar-19 10:46 AM, Thomas Monjalon wrote: > 28/03/2019 11:43, Bruce Richardson: >> On Wed, Mar 27, 2019 at 11:42:40PM +0100, Thomas Monjalon wrote: >>> 27/03/2019 21:33, Stojaczyk, Dariusz: >>>> From: Thomas Monjalon [mailto:thomas@monjalon.net] >>>>> 26/03/2019 19:43, Darek Stojaczyk: >>>>>> We currently initialize rte_alarms after starting >>>>>> to listen for IPC hotplug requests, which gives >>>>>> us a data race window. Upon receiving such hotplug >>>>>> request we always try to set an alarm and this >>>>>> obviously doesn't work if the alarms weren't >>>>>> initialized yet. >>>>>> >>>>>> To fix it, we initialize alarms before starting >>>>>> to listen for IPC hotplug messages. Specifically, >>>>>> we move rte_eal_alarm_init() right after >>>>>> rte_eal_intr_init() as it makes some sense to >>>>>> keep those two close to each other. >>>>> >>>>> I wonder which regression it will bring :) >>>>> The experience shows that we cannot touch this function >>>>> without introducing a regression. Please check twice. >>>> >>>> Hah, ok - I'll check again the possible outcomes of this. >>>> >>>>> >>>>>> Fixes: 244d5130719c ("eal: enable hotplug on multi-process") >>>>>> Cc: Qi Zhang >>>>>> Cc: Anatoly Burakov >>>>>> Cc: stable@dpdk.org >>>>>> >>>>>> Signed-off-by: Darek Stojaczyk >>>>>> --- >>>>>> lib/librte_eal/linux/eal/eal.c | 12 ++++++------ >>>>>> 1 file changed, 6 insertions(+), 6 deletions(-) >>>>> >>>>> You probably need to update the FreeBSD version too. >>>>> >>>> >>>> Oh, that I cannot do. First of all, in bsd code I don't see >>>> rte_mp_dev_hotplug_init() called anywhere, as if bsd >>>> did not listen for IPC hotplug messages at all and hence did >>>> not have any data race in this area. Second, I would be >>>> afraid to touch any bsd code as I'm not running any bsd >>>> system. >>> >>> The problem is the consistency between OSes. >>> May you ask help here? Bruce is maintaining the FreeBSD side. >>> >> I don't think we support IPC or hotplug on BSD, so I don't think this patch >> is relevant on the BSD side. > > Yes, but then, the initialization order is different on Linux and BSD. > I'm thinking about consistency and maintenance ease. > From my cursory inspection, nothing should be broken on FreeBSD as a result of moving alarm API init earlier. -- Thanks, Anatoly