linux-kernel - Re: [PATCH v2 14/14] checkpatch: Error out if deprecated RCU API used

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Date:   Wed, 15 Mar 2023 20:49:14 -0700
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     "Joel Fernandes (Google)" <joel@...lfernandes.org>
Cc:     Andy Whitcroft <apw@...onical.com>, Joe Perches <joe@...ches.com>,
        Dwaipayan Ray <dwaipayanray1@...il.com>,
        Lukas Bulwahn <lukas.bulwahn@...il.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 14/14] checkpatch: Error out if deprecated RCU API used

On Wed, Mar 15, 2023 at 06:19:01PM +0000, Joel Fernandes (Google) wrote:
> Single-argument kvfree_rcu() usage is being deprecated [1] [2]. However,
> till all users are converted, we would like to introduce checkpatch
> errors for new patches submitted.
> 
> This patch adds support for the same. Tested with a trial patch.
> 
> For now, we are only considering usages that don't have compound
> nesting, for example ignore: kvfree_rcu( (rcu_head_obj), rcu_head_name).
> This is sufficient as such usages are unlikely.
> 
> Once all users are converted and we remove the old API, we can also revert this
> checkpatch patch then.
> 
> [1] https://lore.kernel.org/rcu/CAEXW_YRhHaVuq+5f+VgCZM=SF+9xO+QXaxe0yE7oA9iCXK-XPg@mail.gmail.com/
> [2] https://lore.kernel.org/rcu/CAEXW_YSY=q2_uaE2qo4XSGjzs4+C102YMVJ7kWwuT5LGmJGGew@mail.gmail.com/
> 
> Signed-off-by: Joel Fernandes (Google) <joel@...lfernandes.org>

With or without the change suggested below:

Acked-by: Paul E. McKenney <paulmck@...nel.org>

> ---
>  scripts/checkpatch.pl | 9 +++++++++
>  1 file changed, 9 insertions(+)
> 
> diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
> index bd44d12965c9..9da0a3cb1615 100755
> --- a/scripts/checkpatch.pl
> +++ b/scripts/checkpatch.pl
> @@ -6388,6 +6388,15 @@ 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 call the API with an rcu_head object passed, like: k[v]free_rcu(object_ptr, rcu_head_name);  " . $herecurr);

Perhaps also point them at kvfree_rcu_mightsleep()?

							Thanx, Paul

> +			}
> +		}
> +
> +
>  # check for unnecessary "Out of Memory" messages
>  		if ($line =~ /^\+.*\b$logFunctions\s*\(/ &&
>  		    $prevline =~ /^[ \+]\s*if\s*\(\s*(\!\s*|NULL\s*==\s*)?($Lval)(\s*==\s*NULL\s*)?\s*\)/ &&
> -- 
> 2.40.0.rc1.284.g88254d51c5-goog
>