Patch "net: sched: Print msecs when transmit queue time out" has been added to the 6.1-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    net: sched: Print msecs when transmit queue time out

to the 6.1-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     net-sched-print-msecs-when-transmit-queue-time-out.patch
and it can be found in the queue-6.1 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit bfef20f8c285ac59c09bd10035247ab9ad5e816c
Author: Yajun Deng <yajun.deng@xxxxxxxxx>
Date:   Fri Apr 21 16:26:06 2023 +0800

    net: sched: Print msecs when transmit queue time out
    
    [ Upstream commit 2f0f9465ad9fa9c93f30009184c10da0f504f313 ]
    
    The kernel will print several warnings in a short period of time
    when it stalls. Like this:
    
    First warning:
    [ 7100.097547] ------------[ cut here ]------------
    [ 7100.097550] NETDEV WATCHDOG: eno2 (xxx): transmit queue 8 timed out
    [ 7100.097571] WARNING: CPU: 8 PID: 0 at net/sched/sch_generic.c:467
                           dev_watchdog+0x260/0x270
    ...
    
    Second warning:
    [ 7147.756952] rcu: INFO: rcu_preempt self-detected stall on CPU
    [ 7147.756958] rcu:   24-....: (59999 ticks this GP) idle=546/1/0x400000000000000
                          softirq=367      3137/3673146 fqs=13844
    [ 7147.756960]        (t=60001 jiffies g=4322709 q=133381)
    [ 7147.756962] NMI backtrace for cpu 24
    ...
    
    We calculate that the transmit queue start stall should occur before
    7095s according to watchdog_timeo, the rcu start stall at 7087s.
    These two times are close together, it is difficult to confirm which
    happened first.
    
    To let users know the exact time the stall started, print msecs when
    the transmit queue time out.
    
    Signed-off-by: Yajun Deng <yajun.deng@xxxxxxxxx>
    Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
    Stable-dep-of: e316dd1cf135 ("net: don't dump stack on queue timeout")
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
index 7053c0292c335..4023c955036b1 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 int timedout_ms = 0;
 			unsigned int i;
 			unsigned long trans_start;
 
@@ -514,16 +514,16 @@ 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;
+					timedout_ms = jiffies_to_msecs(jiffies - trans_start);
 					atomic_long_inc(&txq->trans_timeout);
 					break;
 				}
 			}
 
-			if (unlikely(some_queue_timedout)) {
+			if (unlikely(timedout_ms)) {
 				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, "NETDEV WATCHDOG: %s (%s): transmit queue %u timed out %u ms\n",
+					  dev->name, netdev_drivername(dev), i, timedout_ms);
 				netif_freeze_queues(dev);
 				dev->netdev_ops->ndo_tx_timeout(dev, i);
 				netif_unfreeze_queues(dev);