On Fri, Oct 8, 2021 at 1:49 PM YiFei Zhu <zhuyifei@xxxxxxxxxx> wrote: > > On Thu, Oct 7, 2021 at 9:34 AM Song Liu <song@xxxxxxxxxx> wrote: > > > > On Thu, Oct 7, 2021 at 9:23 AM YiFei Zhu <zhuyifei@xxxxxxxxxx> wrote: > > > > > > Yeah it felt like we only needed one helper for the parameters and > > > return values to be unambiguous. But if two better avoid confusion for > > > users, we can do that. > > > > > > YiFei Zhu > > > > > [...] > > > > > > > > > > > > One question, if the program want to retrieve existing errno_val, and > > > > > > set a different one, it needs to call the helper twice, right? I guess > > > > > it > > > > > > is possible to do that in one call with a "swap" logic. Would this work? > > > > > > > > > Actually, how about we split this into two helpers:bpf_set_errno() and > > > > > bpf_get_errno(). This should avoid some confusion in long term. > > > > > > > > We've agreed on the single helper during bpf office hours (about 2 weeks > > > > ago), but we can do two, I don't think it matters that much. > > > > I see. If we agreed on this syntax, I won't object. > > > > Thanks, > > Song > > Shall I do the swap then? I don't think it has been discussed, and I > don't see any downsides from doing so, but I don't really see a > scenario in which someone would want to get and set at the same time > either. What kind of swap do you have in mind? IMO it's such a corner case operation that doing 2 calls is fine. I'm assuming the majority of use-cases are: (1) export a custom errno regardless of was was previously done in the chain (2) see if there was already an errno set in the chain and bail out early. I don't see any real need for some efficient swapping and rewriting, but I might be missing something..
