linux-kernel - Re: [patch 42/50] futex: Cleanup stale comments

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Date:   Wed, 28 Jul 2021 20:28:44 -0300
From:   André Almeida <andrealmeid@...labora.com>
To:     Thomas Gleixner <tglx@...utronix.de>,
        LKML <linux-kernel@...r.kernel.org>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Will Deacon <will@...nel.org>,
        Waiman Long <longman@...hat.com>,
        Boqun Feng <boqun.feng@...il.com>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Davidlohr Bueso <dave@...olabs.net>
Subject: Re: [patch 42/50] futex: Cleanup stale comments

Às 12:11 de 13/07/21, Thomas Gleixner escreveu:
> From: Thomas Gleixner <tglx@...utronix.de>
> 
> The futex key reference mechanism is long gone. Cleanup the stale comments
> which still mention it.
> 

There are two comments at futex_wait() that can be cleaned as well:

/*
 * Prepare to wait on uaddr. On success, holds hb lock and increments
 * q.key refs.
 */

/* unqueue_me() drops q.key ref */


> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
> ---
>  kernel/futex.c |  9 +++------
>  1 file changed, 3 insertions(+), 6 deletions(-)
> ---
> diff --git a/kernel/futex.c b/kernel/futex.c
> index b8eab7a2934b..e0f266fa7249 100644
> --- a/kernel/futex.c
> +++ b/kernel/futex.c
> @@ -1354,7 +1354,7 @@ static int lock_pi_update_atomic(u32 __user *uaddr, u32 uval, u32 newval)
>   *  -  1 - acquired the lock;
>   *  - <0 - error
>   *
> - * The hb->lock and futex_key refs shall be held by the caller.
> + * The hb->lock must be held by the caller.
>   *
>   * @exiting is only set when the return value is -EBUSY. If so, this holds
>   * a refcount on the exiting task on return and the caller needs to drop it
> @@ -2621,8 +2621,7 @@ static void futex_wait_queue_me(struct futex_hash_bucket *hb, struct futex_q *q,
>   *
>   * Setup the futex_q and locate the hash_bucket.  Get the futex value and
>   * compare it with the expected value.  Handle atomic faults internally.
> - * Return with the hb lock held and a q.key reference on success, and unlocked
> - * with no q.key reference on failure.
> + * Return with the hb lock held on success, and unlocked on failure.
>   *
>   * Return:
>   *  -  0 - uaddr contains val and hb has been locked;
> @@ -3235,9 +3234,7 @@ static int futex_wait_requeue_pi(u32 __user *uaddr, unsigned int flags,
>  	 * In order for us to be here, we know our q.key == key2, and since
>  	 * we took the hb->lock above, we also know that futex_requeue() has
>  	 * completed and we no longer have to concern ourselves with a wakeup
> -	 * race with the atomic proxy lock acquisition by the requeue code. The
> -	 * futex_requeue dropped our key1 reference and incremented our key2
> -	 * reference count.
> +	 * race with the atomic proxy lock acquisition by the requeue code.
>  	 */
>  
>  	/*
> 
>