linux-kernel - Re: [PATCH tip/core/rcu 19/45] rcutorture: Print negatives for SRCU counter wraparound

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Date:	Wed, 7 May 2014 14:34:26 -0700
From:	josh@...htriplett.org
To:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Cc:	linux-kernel@...r.kernel.org, mingo@...nel.org,
	laijs@...fujitsu.com, dipankar@...ibm.com,
	akpm@...ux-foundation.org, mathieu.desnoyers@...icios.com,
	niv@...ibm.com, tglx@...utronix.de, peterz@...radead.org,
	rostedt@...dmis.org, dhowells@...hat.com, edumazet@...gle.com,
	darren@...art.com, fweisbec@...il.com, oleg@...hat.com, sbw@....edu
Subject: Re: [PATCH tip/core/rcu 19/45] rcutorture: Print negatives for
 SRCU counter wraparound

On Mon, Apr 28, 2014 at 05:25:07PM -0700, Paul E. McKenney wrote:
> From: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
> 
> The srcu_torture_stats() function prints SRCU's per-CPU c[] array with
> an unsigned format, which means that the number one less than zero is
> a very large number.  This commit therefore prints this array with a
> signed format in order to improve readability of the rcutorture output.
> 
> Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>

Nit below; with that:
Reviewed-by: Josh Triplett <josh@...htriplett.org>

>  kernel/rcu/rcutorture.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
> index 3845ea99ccd4..0141fcff6bb9 100644
> --- a/kernel/rcu/rcutorture.c
> +++ b/kernel/rcu/rcutorture.c
> @@ -486,15 +486,16 @@ static void srcu_torture_barrier(void)
>  
>  static void srcu_torture_stats(char *page)
>  {
> +	long c0, c1;
>  	int cpu;
>  	int idx = srcu_ctl.completed & 0x1;
>  
>  	page += sprintf(page, "%s%s per-CPU(idx=%d):",
>  		       torture_type, TORTURE_FLAG, idx);
>  	for_each_possible_cpu(cpu) {
> -		page += sprintf(page, " %d(%lu,%lu)", cpu,
> -			       per_cpu_ptr(srcu_ctl.per_cpu_ref, cpu)->c[!idx],
> -			       per_cpu_ptr(srcu_ctl.per_cpu_ref, cpu)->c[idx]);
> +		c0 = (long)per_cpu_ptr(srcu_ctl.per_cpu_ref, cpu)->c[!idx];
> +		c1 = (long)per_cpu_ptr(srcu_ctl.per_cpu_ref, cpu)->c[idx];
> +		page += sprintf(page, " %d(%ld,%ld)", cpu, c0, c1);

Nit: I'd suggest declaring the variables inside the loop, or not using
intermediate variables at all.

- Josh Triplett
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