From: Simon Horman <horms@kernel.org>
To: Eric Dumazet <edumazet@google.com>
Cc: "David S . Miller" <davem@davemloft.net>,
Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
netdev@vger.kernel.org, eric.dumazet@gmail.com,
Marek Szyprowski <m.szyprowski@samsung.com>
Subject: Re: [PATCH net] net: do not acquire dev->tx_global_lock in netdev_watchdog_up()
Date: Tue, 23 Jun 2026 13:22:30 +0100 [thread overview]
Message-ID: <20260623122230.GK827683@horms.kernel.org> (raw)
In-Reply-To: <20260622110108.69541-1-edumazet@google.com>
On Mon, Jun 22, 2026 at 11:01:08AM +0000, Eric Dumazet wrote:
> 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 <m.szyprowski@samsung.com>
> Closes: https://lore.kernel.org/netdev/a443376e-5187-4268-93b3-58047ef113a8@samsung.com/
> Signed-off-by: Eric Dumazet <edumazet@google.com>
> Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
Reviewed-by: Simon Horman <horms@kernel.org>
next prev parent reply other threads:[~2026-06-23 12:22 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-06-22 11:01 [PATCH net] net: do not acquire dev->tx_global_lock in netdev_watchdog_up() Eric Dumazet
2026-06-23 12:22 ` Simon Horman [this message]
2026-06-23 21:50 ` patchwork-bot+netdevbpf
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