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Miller" , Jakub Kicinski , Paolo Abeni Cc: Simon Horman , netdev@vger.kernel.org, eric.dumazet@gmail.com, Eric Dumazet , Marek Szyprowski Content-Type: text/plain; charset="UTF-8" Marek Szyprowski reported a deadlock during system resume when virtio_net driver is used. The deadlock occurs because netif_device_attach() is called while holding dev->tx_global_lock (via netif_tx_lock_bh() in virtnet_restore_up()). netif_device_attach() calls __netdev_watchdog_up(), which now also tries to acquire dev->tx_global_lock to synchronize with dev_watchdog(). This recursive lock acquisition results in a deadlock. Fix this by removing the tx_global_lock acquisition from netdev_watchdog_up(). The critical state (watchdog_timer and watchdog_ref_held) is already protected by dev->watchdog_lock, which was introduced in the blamed commit. Fixes: 8eed5519e496 ("net: watchdog: fix refcount tracking races") Reported-by: Marek Szyprowski Closes: https://lore.kernel.org/netdev/a443376e-5187-4268-93b3-58047ef113a8@samsung.com/ Signed-off-by: Eric Dumazet Tested-by: Marek Szyprowski --- net/sched/sch_generic.c | 7 ++----- 1 file changed, 2 insertions(+), 5 deletions(-) diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c index 3f1c510df850dbdbaf10d483547c7b1f3a5d5482..ef2b4bf51564173751c74fefe17e3913ed2fa056 100644 --- a/net/sched/sch_generic.c +++ b/net/sched/sch_generic.c @@ -594,9 +594,8 @@ void netdev_watchdog_up(struct net_device *dev) return; if (dev->watchdog_timeo <= 0) dev->watchdog_timeo = 5*HZ; - spin_lock_bh(&dev->tx_global_lock); - spin_lock(&dev->watchdog_lock); + spin_lock_bh(&dev->watchdog_lock); if (!mod_timer(&dev->watchdog_timer, round_jiffies(jiffies + dev->watchdog_timeo))) { if (!dev->watchdog_ref_held) { @@ -605,9 +604,7 @@ void netdev_watchdog_up(struct net_device *dev) dev->watchdog_ref_held = true; } } - spin_unlock(&dev->watchdog_lock); - - spin_unlock_bh(&dev->tx_global_lock); + spin_unlock_bh(&dev->watchdog_lock); } EXPORT_SYMBOL_GPL(netdev_watchdog_up); -- 2.55.0.rc0.786.g65d90a0328-goog