Messages in this thread | | | From | Arnd Bergmann <> | Date | Tue, 18 Dec 2018 17:33:11 +0100 | Subject | Re: [PATCH v2 6/8] socket: Add SO_TIMESTAMP[NS]_NEW |
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On Sat, Dec 15, 2018 at 7:52 PM Willem de Bruijn <willemdebruijn.kernel@gmail.com> wrote: > > > 3 reasons for not doing this: > > > > 1. We do not want to break userspace. If we move this to > > linux/socket.h all the userspace programs now have to include > > linux/socket.h or get this definition through a new libc. > > 2. All the socket options are together in the file asm/socket.h. It > > doesn't seem good for maintainability to move just a few bits > > elsewhere. > > 3. There are only 4 arches (after the series is applied) that have > > their own asm/socket.h. And, this is because there seems to be > > significant differences to asm-generic/socket.h that don't seem > > logically obvious to group and eliminate some of the defines. > > Agreed. All good reasons to leave as is. > > > Also for the other comment. The reason the conditionals were not > > consistent is because they were not consistent to begin with. > > The only difference I see is an inversion of the test. Nesting order > is the same: > > int need_software_tstamp = sock_flag(sk, SOCK_RCVTSTAMP); > ... > if (need_software_tstamp) { > if (!sock_flag(sk, SOCK_RCVTSTAMPNS)) { > } else { > } > } > > vs > > if (sock_flag(sk, SOCK_RCVTSTAMP)) { > if (sock_flag(sk, SOCK_RCVTSTAMPNS)) { > } else { > } > } > > I suggest just adding something like > > if (need_software_tstamp) { > + if (sock_uses_new_tstamp(sk) { > + __sock_recv_timestamp_new(msg, sk, > ktime_to_timespec64(skb->tstamp)); > + } else if (!sock_flag(sk, SOCK_RCVTSTAMPNS)) { > - if (!sock_flag(sk, SOCK_RCVTSTAMPNS)) { > } else { > } > > and > > if (sock_flag(sk, SOCK_RCVTSTAMP)) { > + if (sock_uses_new_tstamp(sk) { > + __sock_recv_timestamp_new(msg, sk, ts); > + else if (sock_flag(sk, SOCK_RCVTSTAMPNS)) { > - if (sock_flag(sk, SOCK_RCVTSTAMPNS)) { > } else { > }
Generally speaking, I think we want the new time handling to be written as the default case rather than have it hidden away in a separate function. If we didn't have the sparc64 quirk with its unusual timeval definition, we'd only need a special flag for the old 32-bit format, but that doesn't work as long we have to support two different 64-bit formats for 64-bit timeval on sparc64 (32 or 64 bit microseconds).
> Note also (2) tentative helper function sock_uses_new_tstamp(const > struct sock *sk) instead of testing sock_flag(sk, SOCK_TSTAMP_NEW) > directly. Since the .._NEW variants are equivalent to .._OLD on 64-bit, > I wonder if we can just compile out the branch. Something like > > static inline bool sock_uses_new_tstamp(const struct sock *sk) { > return (sizeof(time_t) != sizeof(__kernel_long_t)) && > sock_flag(sk, SOCK_TSTAMP_NEW); > }
I think that would break compat handling: when we have a 32-bit user space process, the difference between old and new timestamps is meaningful even on 64-bit kernels, but the distinction is only made all the way down in put_cmsg_compat().
Arnd
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