From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Ananyev, Konstantin" Subject: Re: [PATCH v2] Change alarm cancel function to thread-safe: Date: Tue, 30 Sep 2014 12:30:08 +0000 Message-ID: <2601191342CEEE43887BDE71AB9772582138DE32@IRSMSX105.ger.corp.intel.com> References: <20140926150156.GB5619@hmsreliant.think-freely.org> <2601191342CEEE43887BDE71AB9772582137D88E@IRSMSX104.ger.corp.intel.com> <20140926162134.GE5619@hmsreliant.think-freely.org> <2601191342CEEE43887BDE71AB9772582137D95F@IRSMSX104.ger.corp.intel.com> <20140926193905.GH5619@hmsreliant.think-freely.org> <2601191342CEEE43887BDE71AB9772582138410B@IRSMSX104.ger.corp.intel.com> <20140928204754.GC4012@localhost.localdomain> <2601191342CEEE43887BDE71AB977258213874C5@IRSMSX104.ger.corp.intel.com> <20140929103315.GB12072@BRICHA3-MOBL> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-2" Content-Transfer-Encoding: quoted-printable Cc: "dev-VfR2kkLFssw@public.gmane.org" To: "Wodkowski, PawelX" , "Wodkowski, PawelX" , "Richardson, Bruce" Return-path: In-Reply-To: Content-Language: en-US List-Id: patches and discussions about DPDK List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces-VfR2kkLFssw@public.gmane.org Sender: "dev" > -----Original Message----- > From: dev [mailto:dev-bounces-VfR2kkLFssw@public.gmane.org] On Behalf Of Wodkowski, PawelX > Sent: Tuesday, September 30, 2014 1:05 PM > To: Wodkowski, PawelX; Richardson, Bruce > Cc: dev-VfR2kkLFssw@public.gmane.org > Subject: Re: [dpdk-dev] [PATCH v2] Change alarm cancel function to thread= -safe: >=20 > > -----Original Message----- > > Pawe=B3 > > > > > On Mon, Sep 29, 2014 at 10:11:38AM +0000, Wodkowski, PawelX wrote: > > > > > > > > > > > > Image how you will be damned by someone that not even notice yo= u > > > change > > > > > > and he Is managing some kind of resource based on returned numb= er of > > > > > > set/canceled timers. If you suddenly start returning negative v= alues how > > > those > > > > > > application will behave? Silently changing returned value domai= n is evil in > > > its > > > > > > pure form. > > > > > > > > > > As I can see the impact is very limited. > > > > > > > > It is small impact to DPDK but can be huge to user application: > > > > > > This is why we traditionally have in the release-notes for each relea= se a > > > section dedicated to calling out changes from one release to another.= [See > > > http://dpdk.org/doc/intel/dpdk-release-notes-1.7.0.pdf section 5]. Si= nce > > > from release-to-release there are generally only a couple of changes = - > > > though our next release may be a little different - the actual change= s are > > > clear enough to read about without wading through pages of documentat= ion. > > I > > > thinking calling out the change in both the release notes and the API= docs > > > is sufficient even for a change like this. > > > > > > Basically, I wouldn't let API stability factor in too much in trying = to get > > > a proper fix for this issue. > > > > > > /Bruce > > > > > > > Summarizing all proposed solutions and to be able to produce final patc= h - what > > Is desired behavior after fix? > > > > 1. do we leave as is in Patch v2: > > 1.1 if canceling from other thread - if one of the alarms is executing,= wait to > > finish its execution and then cancel any rearmed alarms. > > 1.2 if canceling from alarm handler and one of the alarms to cancel is = this > > executing callback do no wait for it to finish and cancel anything el= se. > > > > in both cases return number of canceled callbacks. > > > > 2. Do exactly like in 1. but return -EINPROGRESS instead of canceled al= arms > > if one of the alarms to cancel is currently executing callback from a= larm thread > > (information about number of canceled alarms will be lost). >=20 > Or instead of returning -EINPROGRESS set errno to EINPROGRESS (replace > returning error value by setting errno and function can always return num= ber > of canceled callbacks - in error condition 0)? Yes that's looks like a better option.=20 As I remember, inside DPDK we have our own rte_errno, that we can probably = use here. My vote would be for that approach. Konstantin >=20 > > > > 3. refuse to cancel anything if canceling currently executing alarm fro= m alarm > > callback and return -EINPROGRESS otherwise do like in 1.1. > > > > 4. Implement behaviour 1/2/3 (which?) and add API call to interrogate l= ist of > > alarms and retrun state of given alarms(s). > > > > 5. other solutions? > > > > Pawel