Evgeniy Polyakov <[email protected]> wrote:
>
> > What happens if we expect a reply to our message but userspace never sends
> > one? Does the kernel leak memory? Do other processes hang?
>
> It is only advice, one may easily skip seq/ack initialization.
> I could remove it totally from the header, but decided to
> place it to force people to use more reliable protocols over netlink
> by introducing such overhead.
hm. I don't know what that means.
> > > nlh = NLMSG_PUT(skb, 0, msg->seq, NLMSG_DONE, size - sizeof(*nlh));
> > >
> > > data = (struct cn_msg *)NLMSG_DATA(nlh);
> >
> > Unneeded typecast.
>
> Is it really an issue?
Well it adds clutter, but more significantly the cast defeats typechecking.
If someone was to change NLMSG_DATA() to return something other than
void*, the compiler wouldn't complain.
> >
> > Why is spin_lock_bh() being used here?
>
> skb may be delivered in soft irq context, and may race with sending.
> And actually it can be sent from irq context, like it is done in test
> module.
But spin_lock_bh() in irq context will deadlock if interruptible context is
also doing spin_lock_bh().
> > What's all the above code doing? What do `a' and `b' mean? Needs
> > commentary and better-chosen identifiers.
>
> It searches for idx and val to match requested notification,
> if "a" is true - idx is found, if b - val is found.
Let me rephrase: please comment the code and choose identifiers in a manner
which makes it clearer what's going on.
> > Please document all functions with comments. Functions which constitute
> > part of the external API should be commented using the kernel-doc format.
>
> There is Documentation/connector/connector.txt which describes all
> exported functions and structures.
> Should it be ported to docbook?
connector.txt is pitched at about the right level: an in-kernel and
userspace API description. It's rather unclear with respect to mesage
directions though - whether the callback is invoked after kernel->user
messages, or for user->kernel or what, for example. Some clarification
there would help.
But an API description is a different thing from code commentary which
explains the internal design - the latter should be coupled to the code
itself.
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