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    SubjectRe: [PATCH net-next v5 08/22] ethtool: support for netlink notifications
    Wed, Mar 27, 2019 at 10:59:50AM CET, mkubecek@suse.cz wrote:
    >On Wed, Mar 27, 2019 at 10:38:43AM +0100, Jiri Pirko wrote:
    >> Tue, Mar 26, 2019 at 07:17:20PM CET, mkubecek@suse.cz wrote:
    >> >On Tue, Mar 26, 2019 at 05:34:00PM +0100, Jiri Pirko wrote:
    >> >> Mon, Mar 25, 2019 at 06:08:18PM CET, mkubecek@suse.cz wrote:
    >> >> >+void ethtool_notify(struct net_device *dev, struct netlink_ext_ack *extack,
    >> >> >+ unsigned int cmd, u32 req_mask, const void *data)
    >> >> >+{
    >> >> >+ if (unlikely(!ethnl_ok))
    >> >>
    >> >> Why do you need this?
    >> >
    >> >If genetlink family registration fails, ethtool_notify() can be still
    >> >called from other code (e.g. the ethtool ioctl interface). In such case,
    >> >better bail out right away than fail somewhere later (probably after
    >> >preparing the message which can't be sent anyway).
    >>
    >> Again, haven't seen this in any other gen netlink implementation. Why do
    >> they not need it?
    >
    >Do they have notifications triggered from other code by directly calling
    >a function (i.e. not through e.g. a netdev notifier)?

    Okay, got it.


    >
    >An alternative to a flag would be using a RCU pointer for this function
    >(initialized to null and set once the family is registered) which is
    >what e.g. netfilter is doing with its hooks but that would mean that
    >each external notification would use an indirect call.

    It's slow path, I don't think this kind of overhead is of any issue.
    Sounds good.


    >
    >> >> >diff --git a/net/ethtool/netlink.h b/net/ethtool/netlink.h
    >> >> >index b8a6cd3dc3e3..5f2299548915 100644
    >> >> >--- a/net/ethtool/netlink.h
    >> >> >+++ b/net/ethtool/netlink.h
    >> >> >@@ -11,6 +11,8 @@
    >> >> > #define ETHNL_SET_ERRMSG(info, msg) \
    >> >> > do { if (info) GENL_SET_ERR_MSG(info, msg); } while (0)
    >> >> >
    >> >> >+extern u32 ethnl_bcast_seq;
    >> >>
    >> >> Why do you need to have this in header? Second, it is not used by
    >> >> anything. Please don't introduce variables that are not used. Introduce
    >> >> them only in patch where you use it.
    >> >
    >> >It's the same as with ethtool_genl_family. I'll make it static as well
    >> >until it's used in some other file.
    >>
    >> Not only static. You should remove it as you are not using it in this
    >> patch at all.
    >
    >OK
    >
    >Michal

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