Re: [PATCH net] net: fix spurious TX timeout after dev_activate()

[Breno Leitao]

Hello Nicolai,

On Mon, Aug 24, 2026 at 05:13:13PM +0200, Nicolai Buchwitz wrote:
> On 24.8.2026 13:45, Breno Leitao wrote:
> > While debugging another issue today, I found out that my TX queue is
> > stopped for 136.07 years (4294907392 ms).
> 
> nit: 4294907392 ms is ~49.7 days

Lol, let me fix update it.

> >     bnxt_en 0002:01:00.0 eth0: NETDEV WATCHDOG: CPU: 28: transmit queue
> > 23 timed out 4294907392 ms
> > 
> > 4294907392 is not an elapsed time. It is the value of jiffies at that
> > moment: INITIAL_JIFFIES is 4294667296.
> > 
> > dev_activate() runs transition_one_qdisc() over every TX queue, which
> > resets trans_start to 0, and then stamps only queue 0 through
> > netif_trans_update().
> > 
> > Stamp jiffies instead. A queue stopped across dev_activate() now gets a
> > full watchdog_timeo of grace, and is still reported if it is stopped
> > that long.
> > 
> > Fixes: 9b36627acecd ("net: remove dev->trans_start")
> > Cc: stable@xxxxxxxxxxxxxxx
> > Signed-off-by: Breno Leitao <leitao@xxxxxxxxxx>
> > ---
> >  net/sched/sch_generic.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
> > index ef2b4bf515641..4539dc2c6d380 100644
> > --- a/net/sched/sch_generic.c
> > +++ b/net/sched/sch_generic.c
> > @@ -1278,7 +1278,7 @@ static void transition_one_qdisc(struct net_device
> > *dev,
> > 
> >  	rcu_assign_pointer(dev_queue->qdisc, new_qdisc);
> >  	if (need_watchdog_p) {
> > -		WRITE_ONCE(dev_queue->trans_start, 0);
> > +		WRITE_ONCE(dev_queue->trans_start, jiffies);
> >  		*need_watchdog_p = 1;
> >  	}
> >  }
> 
> Follow up or v2: netif_trans_update() in dev_activate() now seems redundant?

Yea, good point, we can get rid of netif_trans_update(), given we have
updated all the trans_start in here.

I will respin this one.

Thanks for the review,
--breno

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