linux-kernel - Re: [PATCH tip/core/rcu 01/12] rcu: Remove rcu_swap

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Date:   Wed, 11 Dec 2019 20:09:11 +0100
From:   Matthias Brugger <matthias.bgg@...il.com>
To:     paulmck@...nel.org,
        "Martin K. Petersen" <martin.petersen@...cle.com>
Cc:     rcu@...r.kernel.org, linux-kernel@...r.kernel.org,
        kernel-team@...com, mingo@...nel.org, jiangshanlai@...il.com,
        dipankar@...ibm.com, akpm@...ux-foundation.org,
        mathieu.desnoyers@...icios.com, josh@...htriplett.org,
        tglx@...utronix.de, peterz@...radead.org, rostedt@...dmis.org,
        dhowells@...hat.com, edumazet@...gle.com, fweisbec@...il.com,
        oleg@...hat.com, joel@...lfernandes.org,
        Bart Van Assche <bart.vanassche@....com>,
        Christoph Hellwig <hch@....de>, Hannes Reinecke <hare@...e.de>,
        Johannes Thumshirn <jthumshirn@...e.de>,
        Shane M Seymour <shane.seymour@....com>,
        Felix Fietkau <nbd@....name>,
        Lorenzo Bianconi <lorenzo.bianconi83@...il.com>,
        Ryder Lee <ryder.lee@...iatek.com>,
        Roy Luo <royluo@...gle.com>, Kalle Valo <kvalo@...eaurora.org>,
        "David S. Miller" <davem@...emloft.net>
Subject: Re: [PATCH tip/core/rcu 01/12] rcu: Remove rcu_swap_protected()



On 11/12/2019 19:37, Paul E. McKenney wrote:
> On Tue, Dec 10, 2019 at 07:51:22PM -0800, Paul E. McKenney wrote:
>> On Tue, Dec 10, 2019 at 10:35:49PM -0500, Martin K. Petersen wrote:
>>>
>>> Paul,
>>>
>>>> Now that the calls to rcu_swap_protected() have been replaced by
>>>> rcu_replace_pointer(), this commit removes rcu_swap_protected().
>>>
>>> It appears there are two callers remaining in Linus' master. Otherwise
>>> looks good to me.
>>
>> I did queue a fix for one of them, and thank you for calling my
>> attention to the new one.  This commit should hit -next soon, so
>> hopefully this will discourage further additions.  ;-)
>>
>>> Reviewed-by: Martin K. Petersen <martin.petersen@...cle.com>
>>
>> Thank you!
> 
> And here is the patch for the new one.
> 
> 							Thanx, Paul
> 
> ------------------------------------------------------------------------
> 
> commit 10699d92c906707d679e28b099cd798a519b4f51
> Author: Paul E. McKenney <paulmck@...nel.org>
> Date:   Wed Dec 11 10:30:21 2019 -0800
> 
>     wireless/mediatek: Replace rcu_swap_protected() with rcu_replace_pointer()
>     
>     This commit replaces the use of rcu_swap_protected() with the more
>     intuitively appealing rcu_replace_pointer() as a step towards removing
>     rcu_swap_protected().
>     
>     Link: https://lore.kernel.org/lkml/CAHk-=wiAsJLw1egFEE=Z7-GGtM6wcvtyytXZA1+BHqta4gg6Hw@mail.gmail.com/
>     Reported-by: Linus Torvalds <torvalds@...ux-foundation.org>
>     Reported-by: "Martin K. Petersen" <martin.petersen@...cle.com>
>     Signed-off-by: Paul E. McKenney <paulmck@...nel.org>
>     Cc: Felix Fietkau <nbd@....name>
>     Cc: Lorenzo Bianconi <lorenzo.bianconi83@...il.com>
>     Cc: Ryder Lee <ryder.lee@...iatek.com>
>     Cc: Roy Luo <royluo@...gle.com>
>     Cc: Kalle Valo <kvalo@...eaurora.org>
>     Cc: "David S. Miller" <davem@...emloft.net>
>     Cc: Matthias Brugger <matthias.bgg@...il.com>
>     Cc: <linux-wireless@...r.kernel.org>
>     Cc: <netdev@...r.kernel.org>
>     Cc: <linux-arm-kernel@...ts.infradead.org>
>     Cc: <linux-mediatek@...ts.infradead.org>
> 
> diff --git a/drivers/net/wireless/mediatek/mt76/agg-rx.c b/drivers/net/wireless/mediatek/mt76/agg-rx.c
> index 53b5a4b..80986ce 100644
> --- a/drivers/net/wireless/mediatek/mt76/agg-rx.c
> +++ b/drivers/net/wireless/mediatek/mt76/agg-rx.c
> @@ -281,8 +281,8 @@ void mt76_rx_aggr_stop(struct mt76_dev *dev, struct mt76_wcid *wcid, u8 tidno)
>  {
>  	struct mt76_rx_tid *tid = NULL;
>  
> -	rcu_swap_protected(wcid->aggr[tidno], tid,
> -			   lockdep_is_held(&dev->mutex));
> +	tid = rcu_swap_protected(wcid->aggr[tidno], tid,
> +				 lockdep_is_held(&dev->mutex));

I suppose you meant: rcu_replace_pointer() here.

Regards,
Matthias

>  	if (tid) {
>  		mt76_rx_aggr_shutdown(dev, tid);
>  		kfree_rcu(tid, rcu_head);
>