linux-kernel - [RFC PATCH v2] netpoll: Remove 4s sleep during carrier detection

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Message-Id: <20230119180008.2156048-1-leitao@debian.org>
Date:   Thu, 19 Jan 2023 10:00:08 -0800
From:   Breno Leitao <leitao@...ian.org>
To:     leitao@...ian.org, kuba@...nel.org, netdev@...r.kernel.org
Cc:     leit@...com, davem@...emloft.net, edumazet@...gle.com,
        pabeni@...hat.com, sa+renesas@...g-engineering.com,
        linux-kernel@...r.kernel.org,
        Michael van der Westhuizen <rmikey@...a.com>
Subject: [RFC PATCH v2] netpoll: Remove 4s sleep during carrier detection

This patch proposes to remove the msleep(4s) during netpoll_setup() if
the carrier appears instantly.

Modern NICs do not seem to have this bouncing problem anymore, and this
sleep slows down the machine boot unnecessarily

Reported-by: Michael van der Westhuizen <rmikey@...a.com>
Signed-off-by: Breno Leitao <leitao@...ian.org>
---
 net/core/netpoll.c | 12 +-----------
 1 file changed, 1 insertion(+), 11 deletions(-)

diff --git a/net/core/netpoll.c b/net/core/netpoll.c
index 9be762e1d042..a089b704b986 100644
--- a/net/core/netpoll.c
+++ b/net/core/netpoll.c
@@ -682,7 +682,7 @@ int netpoll_setup(struct netpoll *np)
 	}
 
 	if (!netif_running(ndev)) {
-		unsigned long atmost, atleast;
+		unsigned long atmost;
 
 		np_info(np, "device %s not up yet, forcing it\n", np->dev_name);
 
@@ -694,7 +694,6 @@ int netpoll_setup(struct netpoll *np)
 		}
 
 		rtnl_unlock();
-		atleast = jiffies + HZ/10;
 		atmost = jiffies + carrier_timeout * HZ;
 		while (!netif_carrier_ok(ndev)) {
 			if (time_after(jiffies, atmost)) {
@@ -704,15 +703,6 @@ int netpoll_setup(struct netpoll *np)
 			msleep(1);
 		}
 
-		/* If carrier appears to come up instantly, we don't
-		 * trust it and pause so that we don't pump all our
-		 * queued console messages into the bitbucket.
-		 */
-
-		if (time_before(jiffies, atleast)) {
-			np_notice(np, "carrier detect appears untrustworthy, waiting 4 seconds\n");
-			msleep(4000);
-		}
 		rtnl_lock();
 	}
 
-- 
2.30.2