6.1-stable review patch. If anyone has any objections, please let me know.
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From: Jakub Kicinski kuba@kernel.org
[ Upstream commit e316dd1cf1358ff9c44b37c7be273a7dc4349986 ]
The top syzbot report for networking (#14 for the entire kernel) is the queue timeout splat. We kept it around for a long time, because in real life it provides pretty strong signal that something is wrong with the driver or the device.
Removing it is also likely to break monitoring for those who track it as a kernel warning.
Nevertheless, WARN()ings are best suited for catching kernel programming bugs. If a Tx queue gets starved due to a pause storm, priority configuration, or other weirdness - that's obviously a problem, but not a problem we can fix at the kernel level.
Bite the bullet and convert the WARN() to a print.
Before:
NETDEV WATCHDOG: eni1np1 (netdevsim): transmit queue 0 timed out 1975 ms WARNING: CPU: 0 PID: 0 at net/sched/sch_generic.c:525 dev_watchdog+0x39e/0x3b0 [... completely pointless stack trace of a timer follows ...]
Now:
netdevsim netdevsim1 eni1np1: NETDEV WATCHDOG: CPU: 0: transmit queue 0 timed out 1769 ms
Alternatively we could mark the drivers which syzbot has learned to abuse as "print-instead-of-WARN" selectively.
Reported-by: syzbot+d55372214aff0faa1f1f@syzkaller.appspotmail.com Reviewed-by: Jiri Pirko jiri@nvidia.com Reviewed-by: Eric Dumazet edumazet@google.com Reviewed-by: Jamal Hadi Salim jhs@mojatatu.com Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Sasha Levin sashal@kernel.org --- net/sched/sch_generic.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c index 4023c955036b1..6ab9359c1706f 100644 --- a/net/sched/sch_generic.c +++ b/net/sched/sch_generic.c @@ -522,8 +522,9 @@ static void dev_watchdog(struct timer_list *t)
if (unlikely(timedout_ms)) { trace_net_dev_xmit_timeout(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); + netdev_crit(dev, "NETDEV WATCHDOG: CPU: %d: transmit queue %u timed out %u ms\n", + raw_smp_processor_id(), + i, timedout_ms); netif_freeze_queues(dev); dev->netdev_ops->ndo_tx_timeout(dev, i); netif_unfreeze_queues(dev);