On Tue, Nov 17, 2020 at 09:38:45AM +0100, Paolo Abeni wrote:
> Hello,
>
> Thank you for the feedback!
>
> On Mon, 2020-11-16 at 23:27 +0100, Luc Van Oostenryck wrote:
> > > @@ -1606,10 +1607,12 @@ bool lock_sock_fast(struct sock *sk);
> > > */
> > > static inline void unlock_sock_fast(struct sock *sk, bool slow)
> > > {
> > > - if (slow)
> > > + if (slow) {
> > > release_sock(sk);
> > > - else
> > > + __release(&sk->sk_lock.slock);
> >
> > The correct solution would be to annotate the declaration of
> > release_sock() with '__releases(&sk->sk_lock.slock)'.
>
> If I add such annotation to release_sock(), I'll get several sparse
> warnings for context imbalance (on each lock_sock()/release_sock()
> pair), unless I also add an '__acquires()' annotation to lock_sock().
>
> The above does not look correct to me ?!? When release_sock() completes
> the socket spin lock is not held.
Yes, that's fine, but I suppose it somehow releases the mutex that
is taken in lock_sock_fast() when returning true, right?
> The annotation added above is
> somewhat an artifact to let unlock_sock_fast() matches lock_sock_fast()
> from sparse perspective. I intentionally avoided changing
> the release_sock() annotation to avoid introducing more artifacts.
>
> The proposed schema is not 100% accurate, as it will also allow e.g. a
> really-not-fitting bh_lock_sock()/unlock_sock_fast() pair, but I could
> not come-up with anything better.
>
> Can we go with the schema I proposed?
Well, I suppose it's a first step.
But can you then add a '__releases(...)' to unlock_sock_fast()?
It's not needed by sparse because it's an inline function and sparse
can then deduce it but it will help to see the pairing with
lock_sock_fast() is OK.
-- Luc
