linux-kernel - Re: [PATCH 00/13] Rename k[v]free_rcu() single argument to k[v]free_rcu

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Message-ID: <ZBI1GhEepro6sufK@pc636>
Date:   Wed, 15 Mar 2023 22:14:02 +0100
From:   Uladzislau Rezki <urezki@...il.com>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Steven Rostedt <rostedt@...dmis.org>,
        Joel Fernandes <joel@...lfernandes.org>,
        Jens Axboe <axboe@...nel.dk>,
        LKML <linux-kernel@...r.kernel.org>, RCU <rcu@...r.kernel.org>,
        "Paul E . McKenney" <paulmck@...nel.org>,
        Oleksiy Avramchenko <oleksiy.avramchenko@...y.com>,
        Philipp Reisner <philipp.reisner@...bit.com>,
        Bryan Tan <bryantan@...are.com>,
        Eric Dumazet <edumazet@...gle.com>,
        Bob Pearson <rpearsonhpe@...il.com>,
        Ariel Levkovich <lariel@...dia.com>,
        Theodore Ts'o <tytso@....edu>, Julian Anastasov <ja@....bg>
Subject: Re: [PATCH 00/13] Rename k[v]free_rcu() single argument to
 k[v]free_rcu_mightsleep()

On Wed, Mar 15, 2023 at 10:07:22PM +0100, Uladzislau Rezki wrote:
> On Wed, Mar 15, 2023 at 04:28:40PM -0400, Steven Rostedt wrote:
> > On Wed, 15 Mar 2023 15:57:02 -0400
> > Joel Fernandes <joel@...lfernandes.org> wrote:
> > 
> > > > I was going to suggest "kvfree_rcu_might_synchronize()" but that's just
> > > > getting ridiculous.  
> > > 
> > > No, synchronize() is incorrect. The code really can sleep for other
> > > reasons like memory allocation. It is not that simple of an
> > > implementation as one may imagine. mightsleep is really the correct
> > > wording IMHO.
> > > 
> > > > Still, I will replace that code back to a kfree() and rcu_synchonize() than
> > > > to let that other name get in.  
> > > 
> > > I think it is too late for that for now, we already have conversions
> > > going into the other subsystems, that means we'll have to redo all
> > > that over again (even if it sounded like a good idea, which it is
> > > not).
> > > 
> > > I would rather you just did: "#define kvfree_rcu_tracing
> > > #kvfree_rcu_mightsleep", or something like that, if it is really a
> > > problem. ;-)
> > > 
> > > Also you are really the first person I know of who has a problem with that name.
> > 
> > I guess you didn't read Jens's reply.
> > 
> > The main issue I have with this, is that "might_sleep" is just an
> > implementation issue. It has *nothing* to do with what the call is about.
> > It is only about freeing something with RCU. It has nothing to do with
> > sleeping. I don't use it because it might sleep. I use it to free something.
> > 
> > If you don't like kvfree_rcu_synchronization() then call it
> > kvfree_rcu_headless() and note that currently it can sleep. Because in
> > the future, if we come up with an implementation where we it doesn't sleep,
> > then we don't need to go and rename all the users in the future.
> > 
> > See where I have the problem with the name "might_sleep"?
> > 
> In that sense there is no need in renaming it. The current name of
> single argument is kvfree_rcu(ptr). It is documented that it can sleep.
> 
> According to its name it is clear that it is headless since there
> is no a second argument.
> 
Forgot to add. I agree with you that currently it can sleep but it
does not mean that a future stays the same, thus there might be an
extra need in renaming again.

--
Uladzislau Rezki