linux-kernel - Re: [PATCH 13/13] rcu/kvfree: Eliminate k[v]free

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Message-ID: <CAEXW_YRhHaVuq+5f+VgCZM=SF+9xO+QXaxe0yE7oA9iCXK-XPg@mail.gmail.com>
Date:   Sun, 5 Mar 2023 05:29:11 -0500
From:   Joel Fernandes <joel@...lfernandes.org>
To:     "Uladzislau Rezki (Sony)" <urezki@...il.com>
Cc:     LKML <linux-kernel@...r.kernel.org>, RCU <rcu@...r.kernel.org>,
        "Paul E . McKenney" <paulmck@...nel.org>,
        Oleksiy Avramchenko <oleksiy.avramchenko@...y.com>,
        Jens Axboe <axboe@...nel.dk>,
        Philipp Reisner <philipp.reisner@...bit.com>,
        Bryan Tan <bryantan@...are.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        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 13/13] rcu/kvfree: Eliminate k[v]free_rcu() single
 argument macro

Hi, All,

On Wed, Feb 1, 2023 at 10:11 AM Uladzislau Rezki (Sony)
<urezki@...il.com> wrote:
>
> For a single argument invocations a new kfree_rcu_mightsleep()
> and kvfree_rcu_mightsleep() macroses are used. This is done in
> order to prevent users from calling a single argument from
> atomic contexts as "_mightsleep" prefix signals that it can
> schedule().
>

Since this commit in -dev branch [1] suggests more users still need
conversion, let us drop this single patch for 6.4 and move the rest of
the series forward? Let me know if you disagree.
https://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git/commit/?h=dev&id=9bf5e3a2626ed474d080f695007541b6ecd6e60b

All -- please supply Ack/Review tags for patches 1-12.

thanks,

 - Joel


> Signed-off-by: Uladzislau Rezki (Sony) <urezki@...il.com>
> ---
>  include/linux/rcupdate.h | 29 ++++++++---------------------
>  1 file changed, 8 insertions(+), 21 deletions(-)
>
> diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
> index 094321c17e48..7571dbfecb18 100644
> --- a/include/linux/rcupdate.h
> +++ b/include/linux/rcupdate.h
> @@ -957,9 +957,8 @@ static inline notrace void rcu_read_unlock_sched_notrace(void)
>
>  /**
>   * kfree_rcu() - kfree an object after a grace period.
> - * @ptr: pointer to kfree for both single- and double-argument invocations.
> - * @rhf: the name of the struct rcu_head within the type of @ptr,
> - *       but only for double-argument invocations.
> + * @ptr: pointer to kfree for double-argument invocations.
> + * @rhf: the name of the struct rcu_head within the type of @ptr.
>   *
>   * Many rcu callbacks functions just call kfree() on the base structure.
>   * These functions are trivial, but their size adds up, and furthermore
> @@ -982,26 +981,18 @@ static inline notrace void rcu_read_unlock_sched_notrace(void)
>   * The BUILD_BUG_ON check must not involve any function calls, hence the
>   * checks are done in macros here.
>   */
> -#define kfree_rcu(ptr, rhf...) kvfree_rcu(ptr, ## rhf)
> +#define kfree_rcu(ptr, rhf) kvfree_rcu_arg_2(ptr, rhf)
> +#define kvfree_rcu(ptr, rhf) kvfree_rcu_arg_2(ptr, rhf)
>
>  /**
> - * kvfree_rcu() - kvfree an object after a grace period.
> - *
> - * This macro consists of one or two arguments and it is
> - * based on whether an object is head-less or not. If it
> - * has a head then a semantic stays the same as it used
> - * to be before:
> - *
> - *     kvfree_rcu(ptr, rhf);
> - *
> - * where @ptr is a pointer to kvfree(), @rhf is the name
> - * of the rcu_head structure within the type of @ptr.
> + * kfree_rcu_mightsleep() - kfree an object after a grace period.
> + * @ptr: pointer to kfree for single-argument invocations.
>   *
>   * When it comes to head-less variant, only one argument
>   * is passed and that is just a pointer which has to be
>   * freed after a grace period. Therefore the semantic is
>   *
> - *     kvfree_rcu(ptr);
> + *     kfree_rcu_mightsleep(ptr);
>   *
>   * where @ptr is the pointer to be freed by kvfree().
>   *
> @@ -1010,13 +1001,9 @@ static inline notrace void rcu_read_unlock_sched_notrace(void)
>   * annotation. Otherwise, please switch and embed the
>   * rcu_head structure within the type of @ptr.
>   */
> -#define kvfree_rcu(...) KVFREE_GET_MACRO(__VA_ARGS__,          \
> -       kvfree_rcu_arg_2, kvfree_rcu_arg_1)(__VA_ARGS__)
> -
> +#define kfree_rcu_mightsleep(ptr) kvfree_rcu_arg_1(ptr)
>  #define kvfree_rcu_mightsleep(ptr) kvfree_rcu_arg_1(ptr)
> -#define kfree_rcu_mightsleep(ptr) kvfree_rcu_mightsleep(ptr)
>
> -#define KVFREE_GET_MACRO(_1, _2, NAME, ...) NAME
>  #define kvfree_rcu_arg_2(ptr, rhf)                                     \
>  do {                                                                   \
>         typeof (ptr) ___p = (ptr);                                      \
> --
> 2.30.2
>