linux-kernel - Re: [PATCH] srcu: Remove dead code in srcu_gp

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Message-Id: <20180214221841.GT3617@linux.vnet.ibm.com>
Date:   Wed, 14 Feb 2018 14:18:41 -0800
From:   "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Byungchul Park <byungchul.park@....com>, jiangshanlai@...il.com,
        josh@...htriplett.org, mathieu.desnoyers@...icios.com,
        linux-kernel@...r.kernel.org, kernel-team@....com
Subject: Re: [PATCH] srcu: Remove dead code in srcu_gp_end()

On Wed, Feb 14, 2018 at 10:00:54AM -0500, Steven Rostedt wrote:
> On Wed, 14 Feb 2018 18:05:24 +0900
> Byungchul Park <byungchul.park@....com> wrote:
> 
> > Of course, compilers will optimize out a dead code. Anyway, remove
> > any dead code for better readibility.
> > 
> > Signed-off-by: Byungchul Park <byungchul.park@....com>
> > ---
> >  kernel/rcu/srcutree.c | 2 --
> >  1 file changed, 2 deletions(-)
> > 
> > diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c
> > index 44bc0fa..829453b 100644
> > --- a/kernel/rcu/srcutree.c
> > +++ b/kernel/rcu/srcutree.c
> > @@ -531,7 +531,6 @@ static void srcu_gp_end(struct srcu_struct *sp)
> >  	unsigned long flags;
> >  	unsigned long gpseq;
> >  	int idx;
> > -	int idxnext;
> 
> Interesting. According to git history, idxnext was never actually used.

Which raises the question of what I intended to do with it.  Reviewing
that function didn't activate any memories, though it did point out a
candidate simplification.

> Reviewed-by: Steven Rostedt (VMware) <rostedt@...dmis.org>

Applied, thank you both!

							Thanx, Paul

> -- Steve
> 
> >  	unsigned long mask;
> >  	struct srcu_data *sdp;
> >  	struct srcu_node *snp;
> > @@ -555,7 +554,6 @@ static void srcu_gp_end(struct srcu_struct *sp)
> >  
> >  	/* Initiate callback invocation as needed. */
> >  	idx = rcu_seq_ctr(gpseq) % ARRAY_SIZE(snp->srcu_have_cbs);
> > -	idxnext = (idx + 1) % ARRAY_SIZE(snp->srcu_have_cbs);
> >  	rcu_for_each_node_breadth_first(sp, snp) {
> >  		spin_lock_irq_rcu_node(snp);
> >  		cbs = false;
>