[PATCH 4.9 32/49] net: watchdog: hold device global xmit lock during tx disable

Greg Kroah-Hartman
2021-02-22T13:51:43Z

From: Edwin Peer <edwin.peer@broadcom.com>

commit 3aa6bce9af0e25b735c9c1263739a5639a336ae8 upstream.

Prevent netif_tx_disable() running concurrently with dev_watchdog() by
taking the device global xmit lock. Otherwise, the recommended:

netif_carrier_off(dev);
netif_tx_disable(dev);

driver shutdown sequence can happen after the watchdog has already
checked carrier, resulting in possible false alarms. This is because
netif_tx_lock() only sets the frozen bit without maintaining the locks
on the individual queues.

Fixes: c3f26a269c24 ("netdev: Fix lockdep warnings in multiqueue configurations.")
Signed-off-by: Edwin Peer <edwin.peer@broadcom.com>
Reviewed-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
include/linux/netdevice.h | 2 ++
1 file changed, 2 insertions(+)

--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -3701,6 +3701,7 @@ static inline void netif_tx_disable(stru

local_bh_disable();
cpu = smp_processor_id();
+ spin_lock(&dev->tx_global_lock);
for (i = 0; i < dev->num_tx_queues; i++) {
struct netdev_queue *txq = netdev_get_tx_queue(dev, i);

@@ -3708,6 +3709,7 @@ static inline void netif_tx_disable(stru
netif_tx_stop_queue(txq);
__netif_tx_unlock(txq);
}
+ spin_unlock(&dev->tx_global_lock);
local_bh_enable();
}