netdev - Re: [PATCH net-next 3/4] mptcp: add MPTCP socket diag interface

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Date:   Thu, 09 Jul 2020 20:00:09 +0200
From:   Paolo Abeni <pabeni@...hat.com>
To:     Jakub Kicinski <kuba@...nel.org>
Cc:     netdev@...r.kernel.org, "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>, mptcp@...ts.01.org,
        Matthieu Baerts <matthieu.baerts@...sares.net>
Subject: Re: [PATCH net-next 3/4] mptcp: add MPTCP socket diag interface

On Thu, 2020-07-09 at 10:34 -0700, Jakub Kicinski wrote:
> On Thu,  9 Jul 2020 15:12:41 +0200 Paolo Abeni wrote:
> > exposes basic inet socket attribute, plus some MPTCP socket
> > fields comprising PM status and MPTCP-level sequence numbers.
> > 
> > Reviewed-by: Mat Martineau <mathew.j.martineau@...ux.intel.com>
> > Signed-off-by: Paolo Abeni <pabeni@...hat.com>
> 
> Any idea why sparse says this:
> 
> include/net/sock.h:1612:31: warning: context imbalance in 'mptcp_diag_get_info' - unexpected unlock
> 
> ? 🤨

AFAICS, that is a sparse false positive, tied
to unlock_sock_fast() usage. 

unlock_sock_fast() conditionally releases the socket lock, according to
it's bool argument, and that fools sparse check: any unlock_sock_fast()
user splats it.

IMHO such warning should be addressed into [un]lock_sock_fast()
function[s] - if possible at all. Outside the scope of this series.

Matthieu suggested adding some comment to note the above, but I boldly
opposed, as current unlock_sock_fast() users don't do that.

Cheers,

Paolo