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

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Date:   Wed, 15 Mar 2023 22:07:22 +0100
From:   Uladzislau Rezki <urezki@...il.com>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Joel Fernandes <joel@...lfernandes.org>,
        Uladzislau Rezki <urezki@...il.com>,
        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 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.

--
Uladzislau Rezki