From:   Uladzislau Rezki <urezki@gmail.com>
Date:   Mon, 6 Mar 2023 17:42:44 +0100
To:     Joel Fernandes <joel@joelfernandes.org>,
        "Paul E. McKenney" <paulmck@kernel.org>
Cc:     "Paul E. McKenney" <paulmck@kernel.org>,
        Uladzislau Rezki <urezki@gmail.com>,
        LKML <linux-kernel@vger.kernel.org>, RCU <rcu@vger.kernel.org>,
        Oleksiy Avramchenko <oleksiy.avramchenko@sony.com>,
        Jens Axboe <axboe@kernel.dk>,
        Philipp Reisner <philipp.reisner@linbit.com>,
        Bryan Tan <bryantan@vmware.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        Eric Dumazet <edumazet@google.com>,
        Bob Pearson <rpearsonhpe@gmail.com>,
        Ariel Levkovich <lariel@nvidia.com>,
        Theodore Ts'o <tytso@mit.edu>, Julian Anastasov <ja@ssi.bg>
Subject: Re: [PATCH 13/13] rcu/kvfree: Eliminate k[v]free_rcu() single
 argument macro
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 <20230306144948.GA3280216@google.com>
 <20230306150108.GT1301832@paulmck-ThinkPad-P17-Gen-1>
 <20230306151203.GC3280216@google.com>
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On Mon, Mar 06, 2023 at 03:12:03PM +0000, Joel Fernandes wrote:
> On Mon, Mar 06, 2023 at 07:01:08AM -0800, Paul E. McKenney wrote:
> [..] 
> > > > 7.	We then evaluate whether further cleanups are needed.
> > > > 
> > > > > > My feeling is
> > > > > > that, we introduced "_mightsleep" macros first and after that try to
> > > > > > convert users.
> > > > 
> > > > > One stopgap could be to add a checkpatch error if anyone tries to use old API,
> > > > > and then in the meanwhile convert all users.
> > > > > Though, that requires people listening to checkpatch complaints.
> > > > 
> > > > Every person who listens is that much less hassle.  It doesn't have to
> > > > be perfect.  ;-)
> > > 
> > > The below checkpatch change can catch at least simple single-arg uses (i.e.
> > > not having compound expressions inside of k[v]free_rcu() args). I will submit
> > > a proper patch to it which we can include in this set.
> > > 
> > > Thoughts?
> > > ---
> > >  scripts/checkpatch.pl | 9 +++++++++
> > >  1 file changed, 9 insertions(+)
> > > 
> > > diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
> > > index 78cc595b98ce..fc73786064b3 100755
> > > --- a/scripts/checkpatch.pl
> > > +++ b/scripts/checkpatch.pl
> > > @@ -6362,6 +6362,15 @@ sub process {
> > >  			}
> > >  		}
> > >  
> > > +# check for soon-to-be-deprecated single-argument k[v]free_rcu() API
> > > +		if ($line =~ /\bk[v]?free_rcu\s*\([^(]+\)/) {
> > > +			if ($line =~ /\bk[v]?free_rcu\s*\([^,]+\)/) {
> > > +				ERROR("DEPRECATED_API",
> > > +				      "Single-argument k[v]free_rcu() API is deprecated, please pass an rcu_head object." . $herecurr);
> > 
> > Nice!
> > 
> > But could you please also tell them what to use instead?  Sure, they
> > could look it up, but if it tells them directly, they are less likely
> > to ignore it.
> 
> Sounds good, I will modify the warning to include the API to call and send
> out a patch soon.
> 
Maybe compile warnings? Or is it too aggressive?

Thanks!

--
Uladzislau Rezki