Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
From:   "Jiri Slaby (SUSE)" <jirislaby@kernel.org>
To:     gregkh@linuxfoundation.org
Cc:     linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org,
        "Jiri Slaby (SUSE)" <jirislaby@kernel.org>
Subject: [PATCH v2 04/14] tty: n_tty: use time_is_before_jiffies() in n_tty_receive_overrun()
Date:   Sun, 27 Aug 2023 09:41:37 +0200
Message-ID: <20230827074147.2287-5-jirislaby@kernel.org>
In-Reply-To: <20230827074147.2287-1-jirislaby@kernel.org>
References: <20230827074147.2287-1-jirislaby@kernel.org>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

The jiffies tests in n_tty_receive_overrun() are simplified ratelimiting
(without locking). We could use struct ratelimit_state and the helpers,
but to me, it occurs to be too complex for this use case.

But the code currently tests both if the time passed (the first
time_after()) and if jiffies wrapped around (the second time_after()).
time_is_before_jiffies() takes care of both, provided overrun_time is
initialized at the allocation time.

So switch to time_is_before_jiffies(), the same what ratelimiting does.

Signed-off-by: Jiri Slaby (SUSE) <jirislaby@kernel.org>
---
 drivers/tty/n_tty.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c
index 7f9fee4cf7cf..c0b23e975877 100644
--- a/drivers/tty/n_tty.c
+++ b/drivers/tty/n_tty.c
@@ -1173,8 +1173,7 @@ static void n_tty_receive_overrun(const struct tty_struct *tty)
 	struct n_tty_data *ldata = tty->disc_data;
 
 	ldata->num_overrun++;
-	if (time_after(jiffies, ldata->overrun_time + HZ) ||
-	    time_after(ldata->overrun_time, jiffies)) {
+	if (time_is_before_jiffies(ldata->overrun_time + HZ)) {
 		tty_warn(tty, "%d input overrun(s)\n", ldata->num_overrun);
 		ldata->overrun_time = jiffies;
 		ldata->num_overrun = 0;
-- 
2.42.0