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=1792569395; b=K/kMxOiMJYkIUC7X5WMmXGU4RdVEsV0FhqfUEFbHTBnQhYWrmnqpmMUPG0TavWSyUmz/ 0wlsIHn9N+8zt+ziLYQdwSIY+8iGtAl9VpM2wPFCKOYIcVX8TNRaXb326RCW01bmaAE7k /+71o185LrUyKyouKXoVjxsxTcXy3xIhlW5xiEK3U9BqRGyGWa8djjtPXuyDZK8gUGBEZ jItRbKUkpsOEENhJN0zPIP3fLrOAjNVwipc8O6Kvz7pB7WHdxYD4YEMC1x10fKbvyeERn Fdm392TWmxPtPNceXNmL8eEodydXrATzHmVNJr1IowUCEqfWqrNT4UqKZp55F3qEzkA== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1792569395; 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=aD7zHKGFhWmsXZ4dKfGhDgucVB9qbuaiYAYuijAD4Ik=; b=OHF//v/MUNT7gfG3eMqNkVw51v62JUvZrfxM/xZzjZPpPBYIfvChsC0VTiHBHrjwsZJV 4FvDtIpqT41t98W1JmyDP3kO8nn0c2yNtgS5Sz1vgU+ekmUS3Cg+jBZarYGlyKXOjo0mD naAPOjzMjKfTsBC2ArQoY79O29kvAYossCe+dSAWruQcOG4q7dUsI1UQYWy3drub3hxCh EWRSKEGse64clIzT8vdeuOjYjkZ+7akTogKUMl90iVU6UMG63I+VEOML/RPGQdwtA9fpj AtX+lo//To3AVIjmBgTZRtlu9qVIkE+yG7aRwnz1gdYhsoO8kUKFu9B9hUUYCdBtZww== 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=KJ0Sxadc; 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)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 91DD8606A319; Wed, 21 Oct 2026 07:56:34 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.2 smtp.subspace.kernel.org 91DD8606A319 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=KJ0Sxadc Received: from [127.0.0.1] (localhost [127.0.0.1]) by localhost (Mailerdaemon) with ESMTPSA id 78072A02DC; Wed, 21 Oct 2026 09:56:29 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=tipi-net.de; s=dkim; t=1792569392; h=from:subject:date:message-id:to:cc:mime-version:content-type: content-transfer-encoding; bh=aD7zHKGFhWmsXZ4dKfGhDgucVB9qbuaiYAYuijAD4Ik=; b=KJ0SxadciDSku0NZHZsFt1RE4hx3/iXqxDCMSflIz7lyr4kdg+DmaetmfOiENIsBOTfB9n lI4sHt6zuaEWpXB2MpwyNOPjzVqRDjH3j5Q3TdcwnX1KRGjmEs3tXO/XwXBUStEZ4s6xdT 6b2Na3ClFX+6CEKy6oHCSRzquVIGvi6CxrTmm3K1yCWBD5mLNTAv5BPiG2LmwndnLQJ3eG ploxes5FXRTBpcTw21LsIFj+gv1ef95fsghYS6mBWpdSmiZhJFKHl+dDE58hByRhJ6n0/W 6ONNeZHHxWWg9RphOUvu3w1gfuPneDH/kEPRRzu12JXV8VYVUcX4jWImKbzLdA== From: Nicolai Buchwitz Subject: [PATCH net v2 0/2] net: usb: cdc_ncm/cdc_mbim: fix netpoll lockup in tx_fixup Date: Wed, 21 Oct 2026 09:56:17 +0200 Message-Id: <20261021-cdc-ncm-netpoll-v2-0-8818965bbb69@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/3WNzQ6CMBCEX8Xs2TVtJfx48j0MB9gusgYLaSvRE N7dgmePM/PNzAKBvXCAy2EBz7MEGV0S5ngA6ht3ZxSbNBhlcq2MQrKEjp7oOE7jMKAtmqLLK2s NEaTW5LmT9754gwRB/TPDq30wxW1rw3oJcfSf/XfWO/z3YtaoMC+NLrNzmbVZdY0yyRafLEO9r usXQRQG0ccAAAA= 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 reproduced the lockup and tested the fix. Patch 2 fixes the same code in cdc_mbim and is untested. 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 | 6 ++++-- drivers/net/usb/cdc_ncm.c | 10 +++++++--- 2 files changed, 11 insertions(+), 5 deletions(-) --- base-commit: 044ad3c90d9d2df2c5cb3325ae17b4e9603a311f change-id: 20261020-cdc-ncm-netpoll-d7a7f69dd2cc Best regards, -- Nicolai Buchwitz