On Fri, Nov 14, 2014 at 8:06 AM, Hannes Frederic Sowa <hannes@xxxxxxxxxxxxxxxxxxx> wrote: > On Fr, 2014-11-14 at 07:33 -0800, Alexei Starovoitov wrote: >> On Fri, Nov 14, 2014 at 4:11 AM, Hannes Frederic Sowa >> <hannes@xxxxxxxxxxxxxxxxxxx> wrote: >> > On Do, 2014-11-13 at 17:36 -0800, Alexei Starovoitov wrote: >> >> the current meaning of BPF_MAP_UPDATE_ELEM syscall command is: >> >> either update existing map element or create a new one. >> >> Initially the plan was to add a new command to handle the case of >> >> 'create new element if it didn't exist', but 'flags' style looks >> >> cleaner and overall diff is much smaller (more code reused), so add 'flags' >> >> attribute to BPF_MAP_UPDATE_ELEM command with the following meaning: >> >> #define BPF_ANY 0 /* create new element or update existing */ >> >> #define BPF_NOEXIST 1 /* create new element if it didn't exist */ >> >> #define BPF_EXIST 2 /* update existing element */ >> > >> > Would a cmpxchg-alike function be handy here? >> >> you mean cmpxchg command in addition to >> update() command ? >> May be... it will have an extra 'value' argument >> (key, old_value, new_value) >> I don't have a use case for it yet though. > > I don't neither. ;) > > I just wanted to bring this up before user space api might get public > and the additional argument might make problems. addition of cmpxchg command won't be a problem obviously. (just another 'new_value' field in existing struct inside bpf_attr union). -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
