On Tue, Sep 30, 2014 at 12:30:08PM +0000, Ananyev, Konstantin wrote: > > > > -----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. > You'll want to document that interface to make sure callers understand that a non-zero return code doesn't automatically mean complete success, but yes, in this case that seems like a pretty reasonable solution. Neil
> 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 >
