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Subject: Re: [PATCH] cw1200: remove an unneeded NULL check on list iterator
From:   Jakob Koschel <jakobkoschel@gmail.com>
In-Reply-To: <20220319063800.28791-1-xiam0nd.tong@gmail.com>
Date:   Sun, 20 Mar 2022 01:47:26 +0100
Cc:     pizza@shaftnet.org, kvalo@kernel.org, davem@davemloft.net,
        kuba@kernel.org, linux-wireless@vger.kernel.org,
        netdev@vger.kernel.org, linux-kernel@vger.kernel.org
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Message-Id: <EFA8A102-59B2-4FC6-AB2E-CA8311E11635@gmail.com>
References: <20220319063800.28791-1-xiam0nd.tong@gmail.com>
To:     Xiaomeng Tong <xiam0nd.tong@gmail.com>
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> On 19. Mar 2022, at 07:38, Xiaomeng Tong <xiam0nd.tong@gmail.com> =
wrote:
>=20
> The list iterator 'item' is always non-NULL so it doesn't need to be
> checked. Thus just remove the unnecessary NULL check. Also remove the
> unnecessary initializer because the list iterator is always =
initialized.
>=20
> Signed-off-by: Xiaomeng Tong <xiam0nd.tong@gmail.com>
> ---
> drivers/net/wireless/st/cw1200/queue.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>=20
> diff --git a/drivers/net/wireless/st/cw1200/queue.c =
b/drivers/net/wireless/st/cw1200/queue.c
> index 12952b1c29df..05392598e273 100644
> --- a/drivers/net/wireless/st/cw1200/queue.c
> +++ b/drivers/net/wireless/st/cw1200/queue.c
> @@ -90,7 +90,7 @@ static void __cw1200_queue_gc(struct cw1200_queue =
*queue,
> 			      bool unlock)
> {
> 	struct cw1200_queue_stats *stats =3D queue->stats;
> -	struct cw1200_queue_item *item =3D NULL, *tmp;
> +	struct cw1200_queue_item *item, *tmp;
> 	bool wakeup_stats =3D false;
>=20
> 	list_for_each_entry_safe(item, tmp, &queue->queue, head) {
> @@ -117,7 +117,7 @@ static void __cw1200_queue_gc(struct cw1200_queue =
*queue,
> 			queue->overfull =3D false;
> 			if (unlock)
> 				__cw1200_queue_unlock(queue);
> -		} else if (item) {
> +		} else {

I don't think this is fixing anything here. You are basically just =
removing
a check that was always true.

I'm pretty sure that this check is here to check if either the list is =
empty or no
element was found. If I'm not wrong, some time ago, lists where not =
circular but
actually pointed to NULL (or the head was NULL) so this check made sense =
but doesn't
anymore.

The appropriate fix would be only setting 'item' when a break is hit and =
keep
the original check.

> 			unsigned long tmo =3D item->queue_timestamp + =
queue->ttl;
> 			mod_timer(&queue->gc, tmo);
> 			cw1200_pm_stay_awake(&stats->priv->pm_state,
> --=20
> 2.17.1
>=20
>=20

I've made those changes already and I'm in the process of upstreaming =
them in an organized
way, so maybe it would make sense to synchronize, so we don't post =
duplicate patches.

        Jakob=