[PATCH] rcu: Remove some superfluous lines

[PATCH] rcu: Remove some superfluous lines

[Peter Zijlstra]

I think you'll find this condition is superfluous, as the whole function
is under #ifdef of that same.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
 kernel/rcu/tree.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 4f7369d54de0..dd2646e56456 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -4237,9 +4237,6 @@ static void rcu_cleanup_dying_idle_cpu(int cpu, struct rcu_state *rsp)
 	struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu);
 	struct rcu_node *rnp = rdp->mynode;  /* Outgoing CPU's rdp & rnp. */
 
-	if (!IS_ENABLED(CONFIG_HOTPLUG_CPU))
-		return;
-
 	/* Remove outgoing CPU from mask in the leaf rcu_node structure. */
 	mask = rdp->grpmask;
 	raw_spin_lock_irqsave_rcu_node(rnp, flags); /* Enforce GP memory-order guarantee. */

Re: [PATCH] rcu: Remove some superfluous lines

[Paul E. McKenney]

On Thu, Mar 10, 2016 at 09:49:04AM +0100, Peter Zijlstra wrote:
> 
> I think you'll find this condition is superfluous, as the whole function
> is under #ifdef of that same.
> 
> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>

Right you are!  It got moved under that #ifdef in the process of merging
the RCU, hotplug, and swait changes, and I failed to notice.  Good catch!

I will apply this to my tree once -rc1 comes out, as it will apply to
-rcu at that point.

Or maybe we should remove the #ifdef and add IS_ENABLED() to the other
functions under that #ifdef.  Thoughts?

							Thanx, Paul

> ---
>  kernel/rcu/tree.c | 3 ---
>  1 file changed, 3 deletions(-)
> 
> diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
> index 4f7369d54de0..dd2646e56456 100644
> --- a/kernel/rcu/tree.c
> +++ b/kernel/rcu/tree.c
> @@ -4237,9 +4237,6 @@ static void rcu_cleanup_dying_idle_cpu(int cpu, struct rcu_state *rsp)
>  	struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu);
>  	struct rcu_node *rnp = rdp->mynode;  /* Outgoing CPU's rdp & rnp. */
> 
> -	if (!IS_ENABLED(CONFIG_HOTPLUG_CPU))
> -		return;
> -
>  	/* Remove outgoing CPU from mask in the leaf rcu_node structure. */
>  	mask = rdp->grpmask;
>  	raw_spin_lock_irqsave_rcu_node(rnp, flags); /* Enforce GP memory-order guarantee. */
> 

Re: [PATCH] rcu: Remove some superfluous lines

[Peter Zijlstra]

On Thu, Mar 10, 2016 at 05:41:46AM -0800, Paul E. McKenney wrote:
> On Thu, Mar 10, 2016 at 09:49:04AM +0100, Peter Zijlstra wrote:
> > 
> > I think you'll find this condition is superfluous, as the whole function
> > is under #ifdef of that same.
> > 
> > Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> 
> Right you are!  It got moved under that #ifdef in the process of merging
> the RCU, hotplug, and swait changes, and I failed to notice.  Good catch!
> 
> I will apply this to my tree once -rc1 comes out, as it will apply to
> -rcu at that point.
> 
> Or maybe we should remove the #ifdef and add IS_ENABLED() to the other
> functions under that #ifdef.  Thoughts?

I'd go with the #ifdef, its the conventional pattern.

Re: [PATCH] rcu: Remove some superfluous lines

[Paul E. McKenney]

On Thu, Mar 10, 2016 at 02:55:00PM +0100, Peter Zijlstra wrote:
> On Thu, Mar 10, 2016 at 05:41:46AM -0800, Paul E. McKenney wrote:
> > On Thu, Mar 10, 2016 at 09:49:04AM +0100, Peter Zijlstra wrote:
> > > 
> > > I think you'll find this condition is superfluous, as the whole function
> > > is under #ifdef of that same.
> > > 
> > > Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> > 
> > Right you are!  It got moved under that #ifdef in the process of merging
> > the RCU, hotplug, and swait changes, and I failed to notice.  Good catch!
> > 
> > I will apply this to my tree once -rc1 comes out, as it will apply to
> > -rcu at that point.
> > 
> > Or maybe we should remove the #ifdef and add IS_ENABLED() to the other
> > functions under that #ifdef.  Thoughts?
> 
> I'd go with the #ifdef, its the conventional pattern.

Longer term, I am moving from #ifdef to IS_ENABLED(), as it makes for
easier detection of compiler errors in oddball combinations of Kconfig
options.  But no point in carrying redundant code in the meantime,
so queued for 4.8.

							Thanx, Paul