From: sashiko-bot@kernel.org
To: "Nicolai Buchwitz" <nb@tipi-net.de>
Cc: linux-usb@vger.kernel.org
Subject: Re: [PATCH net 1/2] net: usb: cdc_ncm: don't enable BHs in tx_fixup under netpoll
Date: Tue, 20 Oct 2026 08:59:17 +0000 [thread overview]
Message-ID: <sashiko-outbox-178670@kernel.org> (raw)
In-Reply-To: <20261020-cdc-ncm-netpoll-v1-1-682184384b49@tipi-net.de>
> netpoll holds the txq lock and calls ndo_start_xmit() with IRQs off but
> BHs on. The spin_unlock_bh() in cdc_ncm_tx_fixup() then runs pending
> softirqs. If one of them transmits, it spins on the txq lock that
> netpoll holds. With netconsole on a cdc_ncm device this ends in a soft
> or hard lockup.
>
> Use spin_lock_irqsave(), which is safe both under netpoll and on the
> normal xmit path.
>
> Fixes: c84ff1d6dff3 ("cdc_ncm: reduce driver latency in the data path")
> Reported-by: Mikkel Eskildsen <mke@visotia.com>
> Closes: https://lore.kernel.org/netdev/PRAP189MB185019A5A8D411482BB6E0CDA9982@PRAP189MB1850.EURP189.PROD.OUTLOOK.COM/
> Tested-by: Mikkel Eskildsen <mke@visotia.com>
> Signed-off-by: Nicolai Buchwitz <nb@tipi-net.de>
Sashiko has reviewed this patch and found no issues.
--
Sashiko AI review · https://sashiko.dev/#/patchset/20261020-cdc-ncm-netpoll-v1-0-682184384b49@tipi-net.de?part=1
next prev parent reply other threads:[~2026-10-20 8:59 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-20 7:16 [PATCH net 0/2] net: usb: cdc_ncm/cdc_mbim: fix netpoll lockup in tx_fixup Nicolai Buchwitz
2026-10-20 7:16 ` [PATCH net 1/2] net: usb: cdc_ncm: don't enable BHs in tx_fixup under netpoll Nicolai Buchwitz
2026-10-20 8:59 ` sashiko-bot [this message]
2026-10-20 7:16 ` [PATCH net 2/2] net: usb: cdc_mbim: " Nicolai Buchwitz
2026-10-20 8:59 ` sashiko-bot
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