linux-kernel - Re: [PATCH 6/7] rcu: rename some CONFIG_PREEMPTION to CONFIG_PREEMPT

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Date:   Wed, 16 Oct 2019 20:00:00 -0700
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     Lai Jiangshan <laijs@...ux.alibaba.com>
Cc:     20191015102402.1978-1-laijs@...ux.alibaba.com,
        linux-kernel@...r.kernel.org,
        Lai Jiangshan <jiangshanlai@...il.com>,
        Josh Triplett <josh@...htriplett.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Joel Fernandes <joel@...lfernandes.org>, rcu@...r.kernel.org
Subject: Re: [PATCH 6/7] rcu: rename some CONFIG_PREEMPTION to
 CONFIG_PREEMPT_RCU

On Wed, Oct 16, 2019 at 11:26:23PM +0800, Lai Jiangshan wrote:
> 
> 
> On 2019/10/16 11:54 上午, Paul E. McKenney wrote:
> > On Tue, Oct 15, 2019 at 10:28:48AM +0000, Lai Jiangshan wrote:
> > > CONFIG_PREEMPTION and CONFIG_PREEMPT_RCU are always identical,
> > > but some code depends on CONFIG_PREEMPTION to access to
> > > rcu_preempt functionalitis. This patch changes CONFIG_PREEMPTION
> > > to CONFIG_PREEMPT_RCU in these cases.
> > > 
> > > Signed-off-by: Lai Jiangshan <jiangshanlai@...il.com>
> > > Signed-off-by: Lai Jiangshan <laijs@...ux.alibaba.com>
> > 
> > I believe that this does not cause problems with Sebastian's patch
> > "[PATCH 27/34] rcu: Use CONFIG_PREEMPTION where appropriate", but could
> > you please check?
> 
> I don't know for which commit the patch "[PATCH 27/34] rcu: Use
> CONFIG_PREEMPTION where appropriate" should be applied against
> after several tries. But I don't think there will be any conflicts
> which this patch by "eye" applying.

Well, git didn't see any either, so it is now applied for review and
testing.  Thank you!

							Thanx, Paul

> Thanks,
> Lai
> 
> 
> 
> > 
> > 							Thanx, Paul
> > 
> > > ---
> > >   kernel/rcu/tree.c       | 4 ++--
> > >   kernel/rcu/tree_stall.h | 6 +++---
> > >   2 files changed, 5 insertions(+), 5 deletions(-)
> > > 
> > > diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
> > > index 7db5ea06a9ed..81eb64fcf5ab 100644
> > > --- a/kernel/rcu/tree.c
> > > +++ b/kernel/rcu/tree.c
> > > @@ -1926,7 +1926,7 @@ rcu_report_unblock_qs_rnp(struct rcu_node *rnp, unsigned long flags)
> > >   	struct rcu_node *rnp_p;
> > >   	raw_lockdep_assert_held_rcu_node(rnp);
> > > -	if (WARN_ON_ONCE(!IS_ENABLED(CONFIG_PREEMPTION)) ||
> > > +	if (WARN_ON_ONCE(!IS_ENABLED(CONFIG_PREEMPT_RCU)) ||
> > >   	    WARN_ON_ONCE(rcu_preempt_blocked_readers_cgp(rnp)) ||
> > >   	    rnp->qsmask != 0) {
> > >   		raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
> > > @@ -2294,7 +2294,7 @@ static void force_qs_rnp(int (*f)(struct rcu_data *rdp))
> > >   		mask = 0;
> > >   		raw_spin_lock_irqsave_rcu_node(rnp, flags);
> > >   		if (rnp->qsmask == 0) {
> > > -			if (!IS_ENABLED(CONFIG_PREEMPTION) ||
> > > +			if (!IS_ENABLED(CONFIG_PREEMPT_RCU) ||
> > >   			    rcu_preempt_blocked_readers_cgp(rnp)) {
> > >   				/*
> > >   				 * No point in scanning bits because they
> > > diff --git a/kernel/rcu/tree_stall.h b/kernel/rcu/tree_stall.h
> > > index 0b75426ebb3e..55f9b84790d3 100644
> > > --- a/kernel/rcu/tree_stall.h
> > > +++ b/kernel/rcu/tree_stall.h
> > > @@ -163,7 +163,7 @@ static void rcu_iw_handler(struct irq_work *iwp)
> > >   //
> > >   // Printing RCU CPU stall warnings
> > > -#ifdef CONFIG_PREEMPTION
> > > +#ifdef CONFIG_PREEMPT_RCU
> > >   /*
> > >    * Dump detailed information for all tasks blocking the current RCU
> > > @@ -215,7 +215,7 @@ static int rcu_print_task_stall(struct rcu_node *rnp)
> > >   	return ndetected;
> > >   }
> > > -#else /* #ifdef CONFIG_PREEMPTION */
> > > +#else /* #ifdef CONFIG_PREEMPT_RCU */
> > >   /*
> > >    * Because preemptible RCU does not exist, we never have to check for
> > > @@ -233,7 +233,7 @@ static int rcu_print_task_stall(struct rcu_node *rnp)
> > >   {
> > >   	return 0;
> > >   }
> > > -#endif /* #else #ifdef CONFIG_PREEMPTION */
> > > +#endif /* #else #ifdef CONFIG_PREEMPT_RCU */
> > >   /*
> > >    * Dump stacks of all tasks running on stalled CPUs.  First try using
> > > -- 
> > > 2.20.1
> > >