From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mx.nabladev.com (mx.nabladev.com [178.251.229.89]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C44813B583D; Tue, 14 Apr 2026 10:07:06 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=178.251.229.89 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776161228; cv=none; b=mEWsS4aQAkJBMLrqnXvB4t2GSM+cFNe4d5Dcn2GoPsfmW2v2JzpELT5PgcQVUSEzFlxE279WIAyvEGM6L1R8boB6IIJ9BcjgyTDOZHhaLk42hyD2uYJkG4X/DxYBpquI73P9AtGsxwHgvqvhfYc2wMwvQA4KeJ+B3uyGry0WOf0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776161228; c=relaxed/simple; bh=U7B3hY316QCp8VRZPEC0bI58dj4yGY1dZwbddcBFGx0=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=BOHS69ROluQUYx9itNNMDK0Jes8i8H7FFX9VM3ak/Rq0g+y90/zrLuWj5dip0RAhwwpJoXrad9cTNgMg5f7Jy7iffxEaC4NbUoa6BnBeO8V2OoM+mgswPPv3gz/qBhK7MtLVAc9GXetZ/VZ4ZdZMpbqwrGbz0AdW4fW6+QjbORg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=nabladev.com; spf=pass smtp.mailfrom=nabladev.com; dkim=pass (2048-bit key) header.d=nabladev.com header.i=@nabladev.com header.b=J3baarwV; arc=none smtp.client-ip=178.251.229.89 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=nabladev.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=nabladev.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=nabladev.com header.i=@nabladev.com header.b="J3baarwV" Received: from [127.0.0.1] (localhost [127.0.0.1]) by localhost (Mailerdaemon) with ESMTPSA id 5EC2010CE86; Tue, 14 Apr 2026 12:07:01 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nabladev.com; s=dkim; t=1776161224; h=from:subject:date:message-id:to:cc:mime-version:content-type: content-transfer-encoding:content-language:in-reply-to:references; bh=nDSQ1qVAQDKVPu+EdG4A07GNZkzB7xDnGkIuGtvgKU4=; b=J3baarwVurbP1YVzghseAT6rMJMudngQIBweegx/JTJmBHZWfLV71D6xr+DoiDZIiqZqUv 1l2JCdzxdbdk3aU754Zh8/ek0ZshytkJnBjnFHXvu/lsI+1Z5Y4SAyvZ8teH18VG97AAq2 m2xhe//rcd8hCUiUG9ZnTKcaKpCKEJj1B7tKb80vWtQJJoF9DZGk9O4NSbsjpTkiyp/fTE T8ErdEdNML+flLwpph1HdjbWp8yU8Hm5iid3YfuvtALAPvKQR0CQ02fyTS5mje5HcDOKVj 5iY5BatTvP35UfyGurPx41QyDgJ2p8aYXw62E7mYEEZ8tIvyIE/5TQVMFlei0w== Message-ID: Date: Tue, 14 Apr 2026 12:07:00 +0200 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [net,PATCH v2] net: ks8851: Reinstate disabling of BHs around IRQ handler To: Sebastian Andrzej Siewior , Jakub Kicinski Cc: netdev@vger.kernel.org, stable@vger.kernel.org, "David S. Miller" , Andrew Lunn , Eric Dumazet , Nicolai Buchwitz , Paolo Abeni , Ronald Wahl , Yicong Hui , linux-kernel@vger.kernel.org, Thomas Gleixner References: <20260408162535.98108-1-marex@nabladev.com> <20260412090141.21bf1534@kernel.org> <2558832d-c821-436d-898d-b708c5e0a228@nabladev.com> <20260412105125.48f0c58f@kernel.org> <20260413125744.TVKkZcEK@linutronix.de> <20260413084445.59fe28d6@kernel.org> <20260413161000.P_SLxmZl@linutronix.de> Content-Language: en-US From: Marek Vasut In-Reply-To: <20260413161000.P_SLxmZl@linutronix.de> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Last-TLS-Session-Version: TLSv1.3 On 4/13/26 6:10 PM, Sebastian Andrzej Siewior wrote: >> TBH changing the driver feels like a workaround / invitation for a >> whack-a-mole game. I'd prefer to fix the skb allocation. > > The problem is that _irq() implicitly disables bh processing but this > does not happen. Forcing this is possible but expensive. > However, I did remove lock from bh_disable() on RT. > > Marek: from which kernel version was this backtrace? That was v6.12.79-rt17-rebase where it was easy to trigger , here is a fresh one from next-20260413 with b44596ffe1b4 ("ARM: Allow to enable RT") from stable-rt added on top: " rcu: INFO: rcu_preempt detected stalls on CPUs/tasks: rcu: Tasks blocked on level-0 rcu_node (CPUs 0-1): P127/5:b..l rcu: (detected by 1, t=2102 jiffies, g=-503, q=1 ncpus=2) task:irq/68-eth1 state:D stack:0 pid:127 tgid:127 ppid:2 task_flags:0x4208040 flags:0x00000000 Call trace: __schedule from schedule_rtlock+0x1c/0x34 schedule_rtlock from rtlock_slowlock_locked+0x548/0x904 rtlock_slowlock_locked from rt_spin_lock+0x60/0x9c rt_spin_lock from ks8851_start_xmit_par+0x74/0x1a8 ks8851_start_xmit_par from netdev_start_xmit+0x20/0x44 netdev_start_xmit from dev_hard_start_xmit+0xd0/0x188 dev_hard_start_xmit from sch_direct_xmit+0xb8/0x25c sch_direct_xmit from __qdisc_run+0x1f8/0x4ec __qdisc_run from qdisc_run+0x1c/0x28 qdisc_run from net_tx_action+0x1f0/0x268 net_tx_action from handle_softirqs+0x1a4/0x270 handle_softirqs from __local_bh_enable_ip+0xcc/0xe0 __local_bh_enable_ip from __alloc_skb+0xd8/0x128 __alloc_skb from __netdev_alloc_skb+0x3c/0x19c __netdev_alloc_skb from ks8851_irq+0x388/0x4d4 ks8851_irq from irq_thread_fn+0x24/0x64 irq_thread_fn from irq_thread+0x178/0x28c irq_thread from kthread+0x12c/0x138 kthread from ret_from_fork+0x14/0x28 Exception stack(0xf4c99fb0 to 0xf4c99ff8) 9fa0: 00000000 00000000 00000000 00000000 9fc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 9fe0: 00000000 00000000 00000000 00000000 00000013 00000000 "