Re: [PATCH 1/3] rcu: Remove unnecessary condition check in rcu_qsctr_help()

From: Paul E. McKenney
Date: Wed Feb 11 2015 - 11:09:37 EST


On Wed, Feb 11, 2015 at 03:42:37PM +0100, Alexander Gordeev wrote:
> In cases ->curtail and ->donetail pointers differ ->rcucblist
> always points to the beginning of the current list and thus
> can not be NULL. Therefore, the check ->rcucblist != NULL is
> redundant and could be removed.
>
> Cc: "Paul E. McKenney" <paulmck@xxxxxxxxxxxxxxxxxx>
> Signed-off-by: Alexander Gordeev <agordeev@xxxxxxxxxx>

Good point, queued for 3.21.

Thanx, Paul

> ---
> kernel/rcu/tiny.c | 3 +--
> 1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/kernel/rcu/tiny.c b/kernel/rcu/tiny.c
> index cc9ceca..d4e7fe5 100644
> --- a/kernel/rcu/tiny.c
> +++ b/kernel/rcu/tiny.c
> @@ -103,8 +103,7 @@ EXPORT_SYMBOL(__rcu_is_watching);
> static int rcu_qsctr_help(struct rcu_ctrlblk *rcp)
> {
> RCU_TRACE(reset_cpu_stall_ticks(rcp));
> - if (rcp->rcucblist != NULL &&
> - rcp->donetail != rcp->curtail) {
> + if (rcp->donetail != rcp->curtail) {
> rcp->donetail = rcp->curtail;
> return 1;
> }
> --
> 1.8.3.1
>

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