linux-kernel - Re: [PATCH 11/24] rcu/tree: Maintain separate array for vmalloc ptrs

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Message-ID: <20200504142549.GH17577@pc636>
Date:   Mon, 4 May 2020 16:25:49 +0200
From:   Uladzislau Rezki <urezki@...il.com>
To:     "Paul E. McKenney" <paulmck@...nel.org>
Cc:     "Uladzislau Rezki (Sony)" <urezki@...il.com>,
        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 11/24] rcu/tree: Maintain separate array for vmalloc ptrs

> > @@ -3072,21 +3105,34 @@ static inline bool queue_kfree_rcu_work(struct kfree_rcu_cpu *krcp)
> >  		krwp = &(krcp->krw_arr[i]);
> >  
> >  		/*
> > -		 * Try to detach bhead or head and attach it over any
> > +		 * Try to detach bkvhead or head and attach it over any
> >  		 * available corresponding free channel. It can be that
> >  		 * a previous RCU batch is in progress, it means that
> >  		 * immediately to queue another one is not possible so
> >  		 * return false to tell caller to retry.
> >  		 */
> > -		if ((krcp->bhead && !krwp->bhead_free) ||
> > +		if ((krcp->bkvhead[0] && !krwp->bkvhead_free[0]) ||
> > +			(krcp->bkvhead[1] && !krwp->bkvhead_free[1]) ||
> >  				(krcp->head && !krwp->head_free)) {
> > -			/* Channel 1. */
> > -			if (!krwp->bhead_free) {
> > -				krwp->bhead_free = krcp->bhead;
> > -				krcp->bhead = NULL;
> > +			/*
> > +			 * Channel 1 corresponds to SLAB ptrs.
> > +			 */
> > +			if (!krwp->bkvhead_free[0]) {
> > +				krwp->bkvhead_free[0] = krcp->bkvhead[0];
> > +				krcp->bkvhead[0] = NULL;
> >  			}
> >  
> > -			/* Channel 2. */
> > +			/*
> > +			 * Channel 2 corresponds to vmalloc ptrs.
> > +			 */
> > +			if (!krwp->bkvhead_free[1]) {
> > +				krwp->bkvhead_free[1] = krcp->bkvhead[1];
> > +				krcp->bkvhead[1] = NULL;
> > +			}
> 
> Why not a "for" loop here?  Duplicate code is most certainly not what
> we want, as it can cause all sorts of trouble down the road.
> 
Agree. Can be done. Thanks :)

--
Vlad Rezki