linux-kernel - Re: [PATCH 03/24] rcu/tree: Use consistent style for comments

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Date:   Fri, 1 May 2020 12:05:55 -0700
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     "Uladzislau Rezki (Sony)" <urezki@...il.com>
Cc:     LKML <linux-kernel@...r.kernel.org>, linux-mm@...ck.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        "Theodore Y . Ts'o" <tytso@....edu>,
        Matthew Wilcox <willy@...radead.org>,
        Joel Fernandes <joel@...lfernandes.org>,
        RCU <rcu@...r.kernel.org>,
        Oleksiy Avramchenko <oleksiy.avramchenko@...ymobile.com>
Subject: Re: [PATCH 03/24] rcu/tree: Use consistent style for comments

On Tue, Apr 28, 2020 at 10:58:42PM +0200, Uladzislau Rezki (Sony) wrote:
> From: "Joel Fernandes (Google)" <joel@...lfernandes.org>
> 
> Simple clean up of comments in kfree_rcu() code to keep it consistent
> with majority of commenting styles.
> 
> Reviewed-by: Uladzislau Rezki <urezki@...il.com>
> Signed-off-by: Joel Fernandes (Google) <joel@...lfernandes.org>
> Signed-off-by: Uladzislau Rezki (Sony) <urezki@...il.com>

Hmmm...

Exactly why is three additional characters per line preferable?  Or in
the case of block comments, either one or two additional lines, depending
on /* */ style?

I am (slowly) moving RCU to "//" for those reasons.  ;-)

							Thanx, Paul

> ---
>  kernel/rcu/tree.c | 16 ++++++++--------
>  1 file changed, 8 insertions(+), 8 deletions(-)
> 
> diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
> index cd61649e1b00..1487af8e11e8 100644
> --- a/kernel/rcu/tree.c
> +++ b/kernel/rcu/tree.c
> @@ -3043,15 +3043,15 @@ static inline bool queue_kfree_rcu_work(struct kfree_rcu_cpu *krcp)
>  static inline void kfree_rcu_drain_unlock(struct kfree_rcu_cpu *krcp,
>  					  unsigned long flags)
>  {
> -	// Attempt to start a new batch.
> +	/* Attempt to start a new batch. */
>  	krcp->monitor_todo = false;
>  	if (queue_kfree_rcu_work(krcp)) {
> -		// Success! Our job is done here.
> +		/* Success! Our job is done here. */
>  		raw_spin_unlock_irqrestore(&krcp->lock, flags);
>  		return;
>  	}
>  
> -	// Previous RCU batch still in progress, try again later.
> +	/* Previous RCU batch still in progress, try again later. */
>  	krcp->monitor_todo = true;
>  	schedule_delayed_work(&krcp->monitor_work, KFREE_DRAIN_JIFFIES);
>  	raw_spin_unlock_irqrestore(&krcp->lock, flags);
> @@ -3151,14 +3151,14 @@ void kfree_call_rcu(struct rcu_head *head, rcu_callback_t func)
>  	unsigned long flags;
>  	struct kfree_rcu_cpu *krcp;
>  
> -	local_irq_save(flags);	// For safely calling this_cpu_ptr().
> +	local_irq_save(flags);	/* For safely calling this_cpu_ptr(). */
>  	krcp = this_cpu_ptr(&krc);
>  	if (krcp->initialized)
>  		raw_spin_lock(&krcp->lock);
>  
> -	// Queue the object but don't yet schedule the batch.
> +	/* Queue the object but don't yet schedule the batch. */
>  	if (debug_rcu_head_queue(head)) {
> -		// Probable double kfree_rcu(), just leak.
> +		/* Probable double kfree_rcu(), just leak. */
>  		WARN_ONCE(1, "%s(): Double-freed call. rcu_head %p\n",
>  			  __func__, head);
>  		goto unlock_return;
> @@ -3176,7 +3176,7 @@ void kfree_call_rcu(struct rcu_head *head, rcu_callback_t func)
>  
>  	WRITE_ONCE(krcp->count, krcp->count + 1);
>  
> -	// Set timer to drain after KFREE_DRAIN_JIFFIES.
> +	/* Set timer to drain after KFREE_DRAIN_JIFFIES. */
>  	if (rcu_scheduler_active == RCU_SCHEDULER_RUNNING &&
>  	    !krcp->monitor_todo) {
>  		krcp->monitor_todo = true;
> @@ -3722,7 +3722,7 @@ int rcutree_offline_cpu(unsigned int cpu)
>  
>  	rcutree_affinity_setting(cpu, cpu);
>  
> -	// nohz_full CPUs need the tick for stop-machine to work quickly
> +	/* nohz_full CPUs need the tick for stop-machine to work quickly */
>  	tick_dep_set(TICK_DEP_BIT_RCU);
>  	return 0;
>  }
> -- 
> 2.20.1
>