linux-kernel - [PATCH] net: sched: print jiffies when transmit queue time out

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Message-Id: <20230419115632.738730-1-yajun.deng@linux.dev>
Date:   Wed, 19 Apr 2023 19:56:32 +0800
From:   Yajun Deng <yajun.deng@...ux.dev>
To:     jhs@...atatu.com, xiyou.wangcong@...il.com, jiri@...nulli.us,
        davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
        pabeni@...hat.com
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        Yajun Deng <yajun.deng@...ux.dev>
Subject: [PATCH] net: sched: print jiffies when transmit queue time out

Although there is watchdog_timeo to let users know when the transmit queue
begin stall, but dev_watchdog() is called with an interval. The jiffies
will always be greater than watchdog_timeo.

To let users know the exact time the stall started, print jiffies when
the transmit queue time out.

Signed-off-by: Yajun Deng <yajun.deng@...ux.dev>
---
 net/sched/sch_generic.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
index a9aadc4e6858..67b78e260d28 100644
--- a/net/sched/sch_generic.c
+++ b/net/sched/sch_generic.c
@@ -502,7 +502,7 @@ static void dev_watchdog(struct timer_list *t)
 		if (netif_device_present(dev) &&
 		    netif_running(dev) &&
 		    netif_carrier_ok(dev)) {
-			int some_queue_timedout = 0;
+			unsigned long some_queue_timedout = 0;
 			unsigned int i;
 			unsigned long trans_start;
 
@@ -514,7 +514,7 @@ static void dev_watchdog(struct timer_list *t)
 				if (netif_xmit_stopped(txq) &&
 				    time_after(jiffies, (trans_start +
 							 dev->watchdog_timeo))) {
-					some_queue_timedout = 1;
+					some_queue_timedout = jiffies - trans_start;
 					atomic_long_inc(&txq->trans_timeout);
 					break;
 				}
@@ -522,8 +522,9 @@ static void dev_watchdog(struct timer_list *t)
 
 			if (unlikely(some_queue_timedout)) {
 				trace_net_dev_xmit_timeout(dev, i);
-				WARN_ONCE(1, KERN_INFO "NETDEV WATCHDOG: %s (%s): transmit queue %u timed out\n",
-				       dev->name, netdev_drivername(dev), i);
+				WARN_ONCE(1, KERN_INFO "NETDEV WATCHDOG: %s (%s): \
+					  transmit queue %u timed out %lu jiffies\n",
+					  dev->name, netdev_drivername(dev), i, some_queue_timedout);
 				netif_freeze_queues(dev);
 				dev->netdev_ops->ndo_tx_timeout(dev, i);
 				netif_unfreeze_queues(dev);
-- 
2.25.1