Messages in this thread |  | | From | Brendan Gregg <> | Date | Tue, 2 Jan 2018 11:46:26 -0800 | Subject | Re: [PATCH v3 net-next 2/5] net: tracepoint: replace tcp_set_state tracepoint with inet_sock_set_state tracepoint |
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On Sat, Dec 30, 2017 at 7:06 PM, Yafang Shao <laoar.shao@gmail.com> wrote: > On Sun, Dec 31, 2017 at 6:33 AM, Brendan Gregg > <brendan.d.gregg@gmail.com> wrote: >> On Tue, Dec 19, 2017 at 7:12 PM, Yafang Shao <laoar.shao@gmail.com> wrote: >>> As sk_state is a common field for struct sock, so the state >>> transition tracepoint should not be a TCP specific feature. >>> Currently it traces all AF_INET state transition, so I rename this >>> tracepoint to inet_sock_set_state tracepoint with some minor changes and move it >>> into trace/events/sock.h. >> >> The tcp:tcp_set_state probe is tcp_set_state(), so it's only going to >> fire for TCP sessions. It's not broken, and we could add a >> sctp:sctp_set_state as well. Replacing tcp:tcp_set_state with >> inet_sk_set_state is feeling like we might be baking too much >> implementation detail into the tracepoint API. >> >> If we must have inet_sk_set_state, then must we also delete tcp:tcp_set_state? >> > > Hi Brendan, > > The reason we have to make this change could be got from this mail > thread, https://patchwork.kernel.org/patch/10099243/ . > > The original tcp:tcp_set_state probe doesn't traced all TCP state transitions. > There're some state transitions in inet_connection_sock.c and > inet_hashtables.c are missed. > So we have to place this probe into these two files to fix the issue. > But as inet_connection_sock.c and inet_hashtables.c are common files > for all IPv4 protocols, not only for TCP, so it is not proper to place > a tcp_ function in these two files. > That's why we decide to rename tcp:tcp_set_state probe to > sock:inet_sock_set_state.
It kinda feels like we are fixing one exposing-implementation problem (the missing state changes, which I'm happy to see fixed), by exposing another (there's no tcp:tcp_set_state because we don't want to put tcp functions in inet*.c files). Anyway...
If I'm to use sock:inet_sock_set_state for TCP tracing, I'd like sk->sk_protocol exposed as a tracepoint argument so I can match on IPPROTO_TCP. Otherwise I'll have to keep digging it out of (void *)skaddr. (And if we're adding arguments, maybe consider sk_family as well, to make it easier to see which address arguments to use).
Brendan
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