[PATCH 5.10.y 1/2] net: annotate accesses to queue->trans_start

[Sasha Levin <sashal@kernel.org>]

From: Eric Dumazet <edumazet@google.com>

[ Upstream commit 5337824f4dc4bb26f38fbbba4ffb425a92803f15 ]

In following patches, dev_watchdog() will no longer stop all queues.
It will read queue->trans_start locklessly.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Backport to 5.15: retain only the transition_one_qdisc() annotation
needed by 82aeed2400786bd3f79d88cb8b8f42e6127e5923 ("net: fix spurious TX
timeout after dev_activate()"). This preserves the zero timestamp while
providing the WRITE_ONCE() context that the target changes to jiffies.

Drop the virtio hunk because this tree has no virtnet_tx_timeout(). Drop
the other annotations and helper conversion because they are unrelated
to the target; no new functions are introduced. The 5.15 watchdog still
holds the transmit locks, so the broader lockless-access preparation is
not required for this dependency.

[ sashal: Reduced backport -- upstream 5337824f4dc4b touches 14 file(s), this
  backport carries 1. Not backported here:
  drivers/net/ethernet/apm/xgene/xgene_enet_main.c
  drivers/net/ethernet/atheros/ag71xx.c
  drivers/net/ethernet/freescale/dpaa/dpaa_eth.c
  drivers/net/ethernet/hisilicon/hns3/hns3_enet.c
  drivers/net/ethernet/ibm/ibmvnic.c
  drivers/net/ethernet/intel/igb/igb_main.c
  drivers/net/ethernet/mellanox/mlx5/core/en/reporter_tx.c
  drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
  ... and 5 more
  This note is generated from the file lists only; see the resolution record
  for the reasoning. ]

Stable-dep-of: 82aeed240078 ("net: fix spurious TX timeout after dev_activate()")
Signed-off-by: Sasha Levin <sashal@kernel.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 243a1d6b349c7..d55b010285739 100644
--- a/net/sched/sch_generic.c
+++ b/net/sched/sch_generic.c
@@ -1149,7 +1149,7 @@ static void transition_one_qdisc(struct net_device *dev,
 
 	rcu_assign_pointer(dev_queue->qdisc, new_qdisc);
 	if (need_watchdog_p) {
-		dev_queue->trans_start = 0;
+		WRITE_ONCE(dev_queue->trans_start, 0);
 		*need_watchdog_p = 1;
 	}
 }
-- 
2.53.0