* [PATCH net] net: fix spurious TX timeout after dev_activate()
@ 2026-08-24 11:45 Breno Leitao
2026-08-24 15:13 ` Nicolai Buchwitz
0 siblings, 1 reply; 5+ messages in thread
From: Breno Leitao @ 2026-08-24 11:45 UTC (permalink / raw)
To: Jamal Hadi Salim, Jiri Pirko, David S. Miller, Eric Dumazet,
Jakub Kicinski, Paolo Abeni, Simon Horman, Florian Westphal
Cc: netdev, linux-kernel, kernel-team, stable, Breno Leitao
While debugging another issue today, I found out that my TX queue is
stopped for 136.07 years (4294907392 ms).
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@vger.kernel.org
Signed-off-by: Breno Leitao <leitao@debian.org>
---
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;
}
}
---
base-commit: 0a0d1d55dad570724bf8c7ea83409639cfb4be9b
change-id: 20260824-trans_start-557ecd4c8866
Best regards,
--
Breno Leitao <leitao@debian.org>
^ permalink raw reply related [flat|nested] 5+ messages in thread* Re: [PATCH net] net: fix spurious TX timeout after dev_activate()
2026-08-24 11:45 [PATCH net] net: fix spurious TX timeout after dev_activate() Breno Leitao
@ 2026-08-24 15:13 ` Nicolai Buchwitz
2026-08-25 8:47 ` Paolo Abeni
2026-08-25 10:36 ` Breno Leitao
0 siblings, 2 replies; 5+ messages in thread
From: Nicolai Buchwitz @ 2026-08-24 15:13 UTC (permalink / raw)
To: Breno Leitao
Cc: Jamal Hadi Salim, Jiri Pirko, David S. Miller, Eric Dumazet,
Jakub Kicinski, Paolo Abeni, Simon Horman, Florian Westphal,
netdev, linux-kernel, kernel-team, stable
Hi Breno
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
>
> 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@vger.kernel.org
> Signed-off-by: Breno Leitao <leitao@debian.org>
> ---
> 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?
>
> ---
> base-commit: 0a0d1d55dad570724bf8c7ea83409639cfb4be9b
> change-id: 20260824-trans_start-557ecd4c8866
>
> Best regards,
> --
> Breno Leitao <leitao@debian.org>
Reviewed-by: Nicolai Buchwitz <nb@tipi-net.de>
Thanks,
Nicolai
^ permalink raw reply [flat|nested] 5+ messages in thread* Re: [PATCH net] net: fix spurious TX timeout after dev_activate()
2026-08-24 15:13 ` Nicolai Buchwitz
@ 2026-08-25 8:47 ` Paolo Abeni
2026-08-25 10:43 ` Breno Leitao
2026-08-25 10:36 ` Breno Leitao
1 sibling, 1 reply; 5+ messages in thread
From: Paolo Abeni @ 2026-08-25 8:47 UTC (permalink / raw)
To: Nicolai Buchwitz, Breno Leitao
Cc: Jamal Hadi Salim, Jiri Pirko, David S. Miller, Eric Dumazet,
Jakub Kicinski, Simon Horman, Florian Westphal, netdev,
linux-kernel, kernel-team, stable
On 8/24/26 5:13 PM, Nicolai Buchwitz wrote:
>> 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?
IMHO should be a follow-up.
/P
^ permalink raw reply [flat|nested] 5+ messages in thread* Re: [PATCH net] net: fix spurious TX timeout after dev_activate()
2026-08-25 8:47 ` Paolo Abeni
@ 2026-08-25 10:43 ` Breno Leitao
0 siblings, 0 replies; 5+ messages in thread
From: Breno Leitao @ 2026-08-25 10:43 UTC (permalink / raw)
To: Paolo Abeni
Cc: Nicolai Buchwitz, Jamal Hadi Salim, Jiri Pirko, David S. Miller,
Eric Dumazet, Jakub Kicinski, Simon Horman, Florian Westphal,
netdev, linux-kernel, kernel-team, stable
On Tue, Aug 25, 2026 at 10:47:13AM +0200, Paolo Abeni wrote:
> On 8/24/26 5:13 PM, Nicolai Buchwitz wrote:
> >> 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?
>
> IMHO should be a follow-up.
Oops, I replied to the other email too early. I'll respin this one and
send a separate follow-up covering netif_trans_update.
In that follow-up (net-next material0, I can probably simplify
need_watchdog as well.
Thanks for the guidance,
--breno
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH net] net: fix spurious TX timeout after dev_activate()
2026-08-24 15:13 ` Nicolai Buchwitz
2026-08-25 8:47 ` Paolo Abeni
@ 2026-08-25 10:36 ` Breno Leitao
1 sibling, 0 replies; 5+ messages in thread
From: Breno Leitao @ 2026-08-25 10:36 UTC (permalink / raw)
To: Nicolai Buchwitz
Cc: Jamal Hadi Salim, Jiri Pirko, David S. Miller, Eric Dumazet,
Jakub Kicinski, Paolo Abeni, Simon Horman, Florian Westphal,
netdev, linux-kernel, kernel-team, stable
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@vger.kernel.org
> > Signed-off-by: Breno Leitao <leitao@debian.org>
> > ---
> > 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
--
pw-bot: cr
^ permalink raw reply [flat|nested] 5+ messages in thread
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Thread overview: 5+ messages (download: mbox.gz follow: Atom feed
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2026-08-24 11:45 [PATCH net] net: fix spurious TX timeout after dev_activate() Breno Leitao
2026-08-24 15:13 ` Nicolai Buchwitz
2026-08-25 8:47 ` Paolo Abeni
2026-08-25 10:43 ` Breno Leitao
2026-08-25 10:36 ` Breno Leitao
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