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

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Date:   Wed, 11 Dec 2019 15:12:39 -0800
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     Matthias Brugger <matthias.bgg@...il.com>
Cc:     "Martin K. Petersen" <martin.petersen@...cle.com>,
        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 Wed, Dec 11, 2019 at 08:09:11PM +0100, Matthias Brugger wrote:
> 
> 
> 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 Now that the calls to rcu_swap_protected() have been replaced by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.

Indeed I did, and thank you for catching this!  Bad patch day here.  :-/

Update below...

							Thanx, Paul

------------------------------------------------------------------------

commit ad5572b091429a45e863acaa6a36cf396d44f58d
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>
    [ paulmck: Apply Matthias Brugger feedback. ]
    Signed-off-by: Paul E. McKenney <paulmck@...nel.org>
    Reviewed-by: "Martin K. Petersen" <martin.petersen@...cle.com>
    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..59c1878 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_replace_pointer(wcid->aggr[tidno], tid,
+				  lockdep_is_held(&dev->mutex));
 	if (tid) {
 		mt76_rx_aggr_shutdown(dev, tid);
 		kfree_rcu(tid, rcu_head);