> -----Original Message----- > From: dev [mailto:dev-bounces at dpdk.org] On Behalf Of Wodkowski, PawelX > Sent: Tuesday, September 30, 2014 1:05 PM > To: Wodkowski, PawelX; Richardson, Bruce > Cc: dev at dpdk.org > Subject: Re: [dpdk-dev] [PATCH v2] Change alarm cancel function to > thread-safe: > > > -----Original Message----- > > Pawe? > > > > > 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 you > > > change > > > > > > and he Is managing some kind of resource based on returned number of > > > > > > set/canceled timers. If you suddenly start returning negative > > > > > > values how > > > those > > > > > > application will behave? Silently changing returned value domain 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 release 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]. Since > > > from release-to-release there are generally only a couple of changes - > > > though our next release may be a little different - the actual changes are > > > clear enough to read about without wading through pages of documentation. > > 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 patch - > > 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 else. > > > > in both cases return number of canceled callbacks. > > > > 2. Do exactly like in 1. but return -EINPROGRESS instead of canceled alarms > > if one of the alarms to cancel is currently executing callback from alarm > > thread > > (information about number of canceled alarms will be lost). > > Or instead of returning -EINPROGRESS set errno to EINPROGRESS (replace > returning error value by setting errno and function can always return number > of canceled callbacks - in error condition 0)?
Yes that's looks like a better option. 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 > > > > > 3. refuse to cancel anything if canceling currently executing alarm from > > alarm > > callback and return -EINPROGRESS otherwise do like in 1.1. > > > > 4. Implement behaviour 1/2/3 (which?) and add API call to interrogate list > > of > > alarms and retrun state of given alarms(s). > > > > 5. other solutions? > > > > Pawel
