Hi Gaetan From: Gaëtan Rivet, Monday, January 8, 2018 12:58 PM > Hi Matan, > > Sorry for the delay on this. >
It's OK in spite of I need to fetch it back :) > On Wed, Dec 20, 2017 at 10:58:29AM +0000, Matan Azrad wrote: > > Hi Gaetan > > > > > -----Original Message----- > > > From: Gaëtan Rivet [mailto:gaetan.ri...@6wind.com] > > > Sent: Wednesday, December 20, 2017 12:22 AM > > > To: Matan Azrad <ma...@mellanox.com> > > > Cc: Adrien Mazarguil <adrien.mazarg...@6wind.com>; Thomas Monjalon > > > <tho...@monjalon.net>; dev@dpdk.org > > > Subject: Re: [PATCH v3 6/6] net/failsafe: fix removed device > > > handling > > > > > > Hi Matan, > > > > > > On Tue, Dec 19, 2017 at 05:10:15PM +0000, Matan Azrad wrote: > > > > There is time between the physical removal of the device until > > > > sub-device PMDs get a RMV interrupt. At this time DPDK PMDs and > > > > applications still don't know about the removal and may call > > > > sub-device control operation which should return an error. > > > > > > > > In previous code this error is reported to the application > > > > contrary to fail-safe principle that the app should not be aware of > device removal. > > > > > > > > Add an removal check in each relevant control command error flow > > > > and prevent an error report to application when the sub-device is > removed. > > > > > > > > Fixes: a46f8d5 ("net/failsafe: add fail-safe PMD") > > > > Fixes: b737a1e ("net/failsafe: support flow API") > > As stated previously, please do not include those fixes lines. > > > > > > > > > Signed-off-by: Matan Azrad <ma...@mellanox.com> > > > > --- > > > > > > <snip> > > > > > > > +/* > > > > + * Check if error should be reported to the user. > > > > + */ > > > > +static inline bool > > > > +fs_is_error(struct sub_device *sdev, int err) { > > > > + /* A device removal shouldn't be reported as an error. */ > > > > + if (err == 0 || sdev->remove == 1 || err == -EIO) > > > > + return false; > > > > + return true; > > > > +} > > > > > > This is better, thanks. > > > > > > However is there a reason you did not follow the same pattern as > > > ethdev with eth_err? I see the two functions as similar in their > > > intent, making them close to each other would be clearer to a reader > > > being familiar with the ethdev API and that would be interested in fail- > safe. > > > > > > What do you think? > > > > > > > I think that there is a real different between eth_err function to > fs_is_error: > > ethdev uses eth_err function to adjust removal return value to be -EIO. > > fail-safe uses fs_is_error function to check if an error should be reported > > to > the user to save the fail-safe principle that the app should not be aware of > device removal - this is the main idea that also causes me to change the > name from fs_is_removed to fs_is_error. > > I would have preferred if it followed the same pattern as ethdev (that > function be used to adjust the return value, not performing a flag check). > > While better on its own, the pattern: > > if (fs_is_error(sdev, err)) { > ERROR("xxxx"); > return err; > } > > is dangerous, as then the author is forbidden from returning err, assuming > err could be -EIO. He or she would be forced to return an explicit "0". > To be clear, here would be an easy mistake to do: > > if (fs_is_error(sdev, err)) { > ERROR("xxxx"); > } > return err; > > And this kind of code-flow is not unusual, or even unwanted. > I dislike having this kind of implicit rule derived from using a helper such > as > fs_is_error(). > > The alternative > > if ((err = fs_err(sdev, err))) { > ERROR("xxxx"); > return err; > } > > Forces the value err to be set to the correct one. > Good point, will change it. > This mistake can already be found in your patch: > > > @@ -150,7 +150,7 @@ > > continue; > > local_ret = rte_flow_destroy(PORT_ID(sdev), > > flow->flows[i], error); > > - if (local_ret) { > > + if (fs_is_error(sdev, local_ret)) { > > ERROR("Failed to destroy flow on sub_device %d: %d", > > i, local_ret); > > if (ret == 0) > Sorry, I can't see any issue here. > Your environment does not include the function, but this is within > fs_flow_destroy (please update to include the context by the way it helps a > lot the review :). Afterward, line 162 ret is directly used as return value. > I don't understand what do you mean. > Also, fs_err() would need to transform rte_errno when relevant (mostly in > failsafe_flow.c I think). > Your suggestion is always to update rte_errno to 0 in case the error is because of removal? > This is the kind of subtlety that needs to be avoided when designing APIs, > even internal ones. This will induce errors afterward and complicate the > maintenance of the codebase. > Thanks for the lesson! > Best regards, > > -- > Gaëtan Rivet > 6WIND
