linux-kernel - Re: [PATCH 04/13] tracing: Rename kvfree_rcu() to kvfree_rcu

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Date:   Wed, 15 Mar 2023 17:37:30 -0700
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     Jens Axboe <axboe@...nel.dk>
Cc:     Steven Rostedt <rostedt@...dmis.org>,
        Uladzislau Rezki <urezki@...il.com>,
        LKML <linux-kernel@...r.kernel.org>, RCU <rcu@...r.kernel.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 04/13] tracing: Rename kvfree_rcu() to
 kvfree_rcu_mightsleep()

On Wed, Mar 15, 2023 at 05:19:18PM -0600, Jens Axboe wrote:
> On 3/15/23 4:36 PM, Steven Rostedt wrote:
> > On Thu, 9 Mar 2023 14:45:21 +0100
> > Uladzislau Rezki <urezki@...il.com> wrote:
> > 
> >>> The kvfree_rcu()'s single argument name is deprecated therefore
> >>> rename it to kvfree_rcu_mightsleep() variant. The goal is explicitly
> >>> underline that it is for sleepable contexts.
> >>>
> >>> Cc: Steven Rostedt (VMware) <rostedt@...dmis.org>
> >>> Signed-off-by: Uladzislau Rezki (Sony) <urezki@...il.com>
> >>>  
> >> Could you please add you reviwed-by or Acked-by tags so we can bring
> >> our series with renaming for the next merge window?
> > 
> > I don't know. Perhaps we should just apply this patch and not worry about
> > sleeping and whatnot.

That does work, and I am guessing that the size increase is not a big
problem for you there.

> That's a cop out, just removing the one case you care about. Fact is
> the naming is awful, and the 1/2 argument thing is making it worse.
> If a big change is warranted, why not do it right and ACTUALLY
> get it right?

You both do realize that the kvfree_rcu_mightsleep() definition is
already in mainline, right?

Anyway, to sum up, kvfree_rcu_mightsleep()--or whatever the entire
community eventually decides to name it--can do any of the following:

1.	Put the pointer into an already allocated array of pointers.

2.	Allocate a new array of pointers, have the allocation succeed
	without sleeping, then put the pointer into an already allocated
	array of pointers.

3.	Allocate a new array of pointers, have the allocation succeed
	after sleeping, then put the pointer into an already allocated
	array of pointers.

4.	Attempt to allocate a new array of pointers, have the allocation
	fail (presumably after sleeping), then invoke synchronize_rcu()
	directly.

Too much fun!  ;-)

							Thanx, Paul