From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=194.13.80.246 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1792848220; b=xrwrfWJsAORQo1Lm+SrS3sCaG/gf/J8aG+run62dsWcepQI7Adc1LDDPsYRD8EOmqTS+ Bh0P/qWN9Xop6QriZXIGSFuGbxBJs3ZubWaDXPQpUGuHa6KxelHdjpFI9kM0V0uwUhCoS eeKnMyBI6ndtYhhh0nfwXU23GhaUEjM+ZS/w81EOha2Gj9ob9i81O9nSbsUJBTh8SL/qf 94+V3uYgbBePJ/p8QGU/of3PAmJan2yudmaV5fn4Q4Kjk/+abFtr57bmewyTwjzSA3WZj uOmXtoy09Cjg+XulsQErC9XTEIMHRW5NFd8OmX7G6pZN4Y1hkv4YcQ/PVOM0lBxfSrw== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1792848220; h=DMARC-Filter:Received:DKIM-Signature:From:Subject:Date:Message-Id: MIME-Version:Content-Type:Content-Transfer-Encoding:X-B4-Tracking: X-Change-ID:To:Cc:X-Mailer:X-Last-TLS-Session-Version; bh=p6phy3NP+L8YktmM+nQw4wId5NrdzZO4MGgGl8ypPUg=; b=RSF/1HJS+QnRrvfa7rExoYLQEPj7wkpDEU3ePKXn2cAH9HwAtskjm2Op7toV5J8GIbsj n2FnccBjOIV2xRvRjQj21jBA273Z0fCs1+gOGAwnVn4fbdo/QP8dqKSadbOv/yOjCL8Hb na9MQX3JQagGFaSzbIYClj1lkboaNCPN5I7toU9kKNkcs3+CYy9C62TZ4KD/oA2pZAY4m AQOcTSYPlvUxJs6daDZYgABHpYhQ9OWQ3XcaPNQEITN8DVfOyaMoALRWI1mOEwRwoelEN tPuUT8LMUMtDij/mZvD0/8Pa2F8I98jGTAbOv8EKFDhvcHvz+44edo9Xmdbnh9xCf4Q== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=none header.from=tipi-net.de; spf=pass smtp.mailfrom=tipi-net.de; dkim=pass header.d=tipi-net.de header.i=@tipi-net.de header.a=rsa-sha256 header.s=dkim header.b=BsWiFEiy; arc=none smtp.remote-ip=194.13.80.246 Received: from mail.tipi-net.de (mail.tipi-net.de [194.13.80.246]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A8985606A31D; Sat, 24 Oct 2026 13:23:38 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.2 smtp.subspace.kernel.org A8985606A31D Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=tipi-net.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=tipi-net.de Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=tipi-net.de header.i=@tipi-net.de header.a=rsa-sha256 header.s=dkim header.b=BsWiFEiy Received: from [127.0.0.1] (localhost [127.0.0.1]) by localhost (Mailerdaemon) with ESMTPSA id 831B0A15A3; Sat, 24 Oct 2026 15:23:31 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=tipi-net.de; s=dkim; t=1792848215; h=from:subject:date:message-id:to:cc:mime-version:content-type: content-transfer-encoding; bh=p6phy3NP+L8YktmM+nQw4wId5NrdzZO4MGgGl8ypPUg=; b=BsWiFEiy81tuti50BNPS58/f3aiwyiyoFfLBnFN6TKt4iVoj3mbFhjh7vHQxk2wwJPlIWl QmPGbGyIgKP5RGokXnLSJcf7rLz9UnL5ZiegW/z3Gl0VRfy9/qdyJlyPYh6QlsZCWNJHME VIDB0in6ChGfcYWC5VAOOQ8AJUBdM4sWW17nCZuGaMLuoxHP5fEjo1pZBKk+sFNEDfbzmO UsvX29fnjMGjmDeYlb/iFmqdDotiWYPPygUA/pjUAjI/fIqz7B207X3QfjQFNWh6hpFUBx gmR9f4XFXsXVzD5F32uiMsZN041ld5UVOlaM5ZMM6PP/ZG/o0W6UibU72kZzAA== From: Nicolai Buchwitz Subject: [PATCH net v3 0/2] net: usb: cdc_ncm/cdc_mbim: fix netpoll lockup in tx_fixup Date: Sat, 24 Oct 2026 15:23:05 +0200 Message-Id: <20261024-cdc-ncm-netpoll-v3-0-6284ca03f967@tipi-net.de> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-B4-Tracking: v=1; b=H4sIAAAAAAAC/3XNTQ6CMBAF4KuQWVtDC5biynsYF/QHGaOFtLXRE O5uqRujcTkzb743gzcOjYd9MYMzET2ONg3VpgA1dPZsCOo0AysZpyUridKKWHUj1oRpvF6Jbrq m563WTClIX5MzPT6yeIQUgtN76e/yYlRYrTU2oA+je+beSHP4b0WkpCRcMCrqStSybg8BJ1zPW 22yH9mnQH8FlgQhqGj5TkrJv4RlWV60htN8CQEAAA== X-Change-ID: 20261020-cdc-ncm-netpoll-d7a7f69dd2cc To: Oliver Neukum , Andrew Lunn , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , =?utf-8?q?Sjur_Br=C3=A6ndeland?= , Alexey Orishko , =?utf-8?q?Bj=C3=B8rn_Mork?= , Greg Suarez Cc: Breno Leitao , linux-usb@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, Nicolai Buchwitz , Mikkel Eskildsen X-Mailer: b4 0.16.0 X-Last-TLS-Session-Version: TLSv1.3 Mikkel reported lockups with netconsole on a cdc_ncm device. Further analysis showed that netpoll calls ndo_start_xmit() with IRQs off but BHs on while holding the txq lock, and the spin_unlock_bh() in the tx_fixup paths runs pending softirqs. A transmit from one of them then spins on that txq lock. Patch 1 fixes cdc_ncm. Mikkel tested the v2 version of it. Patch 2 fixes the same code in cdc_mbim and is untested. Changes in v3: - Use plain spin_lock() instead of spin_lock_irqsave() (Jakub) - Drop Tested-by and Reviewed-by tags since the locking changed - Link to v2: https://lore.kernel.org/r/20261021-cdc-ncm-netpoll-v2-0-8818965bbb69@tipi-net.de Changes in v2: - Reverse xmas in patch 1 - Link to v1: https://lore.kernel.org/r/20261020-cdc-ncm-netpoll-v1-0-682184384b49@tipi-net.de Signed-off-by: Nicolai Buchwitz --- Nicolai Buchwitz (2): net: usb: cdc_ncm: don't enable BHs in tx_fixup under netpoll net: usb: cdc_mbim: don't enable BHs in tx_fixup under netpoll drivers/net/usb/cdc_mbim.c | 5 +++-- drivers/net/usb/cdc_ncm.c | 7 +++++-- 2 files changed, 8 insertions(+), 4 deletions(-) --- base-commit: 044ad3c90d9d2df2c5cb3325ae17b4e9603a311f change-id: 20261020-cdc-ncm-netpoll-d7a7f69dd2cc Best regards, -- Nicolai Buchwitz