From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 998A717DE36; Wed, 22 Apr 2026 18:23:08 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776882188; cv=none; b=gVWOcKCGTGHtKyE7zN85BqcL34A2BqVyMDnLfvD/ZTC2+F2KCZRccFS9ABxhkT0f6cSMP4/VYXG+N6J65QyGywap6cgLf2jk8mqsJQPtD5bC5VYGDAyg1jMSJx2/wyEA8Oba8V81u84ja7yTwbRAYj9+sktZPpB9Fj0En2+vnN8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776882188; c=relaxed/simple; bh=ObVVfZ7MFRaxaEq78UjYsEvYcdtg2AtIl4XwzsM5VaE=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=tD/gOBfUKyS0hVp+wHSfpA+Vu75eXiyQUSXAtEt7t6q8r0K351siMBI/+fBzU+HWC4Yl8Lxrp2lDuRXdkhMXV9yaH8lrZCdlJK+RGLcChkMR/xbzkTbnAzXIextMROJr2ZrUgIrSL7K/CbNVobhB9mgJu3lgVa7gzcOW3d7pbFM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=p7q0e6QS; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="p7q0e6QS" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D9463C19425; Wed, 22 Apr 2026 18:23:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1776882188; bh=ObVVfZ7MFRaxaEq78UjYsEvYcdtg2AtIl4XwzsM5VaE=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=p7q0e6QSbMf6LZdq+iHFpNWQUhWS/t9eaSBbO1iIChuv1F2ivt5WfcEUr82CNscQJ +pSsUCNyQ6BZIUr0+cfBImsWepP1fVPPitudPcm0N6k+9O7BfOPpY/gfj2JNmHzkxw 30SDQxHlItKU6V/CTRaAPTPdYGFoaTwoGqw2JNJdT7k9GUoFcP9pI9rrV3TRWNNzEV c+eEEYNeoUGbJTTW+zhzD2NYy5EPodyHPAvMJAMQMNjcTUYFtXH0OPnMjTcFi+ykT+ H7jJWe7C+3GnAQ4hplSbrMftJKPjcrp7PTHyMQZphhjjZadttiMjnGDyByIVVorliU LUBQH3xB6Vpcg== Date: Wed, 22 Apr 2026 19:23:02 +0100 From: Simon Horman To: Daniel Golle Cc: "Chester A. Unal" , Andrew Lunn , Vladimir Oltean , "David S. Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Matthias Brugger , AngeloGioacchino Del Regno , Russell King , Christian Marangi , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-mediatek@lists.infradead.org, Frank Wunderlich , John Crispin Subject: Re: [PATCH net v2] net: dsa: mt7530: fix .get_stats64 sleeping in atomic context Message-ID: <20260422182302.GR651125@horms.kernel.org> References: <58aff8b5b1d691872342a6ffd3315f27854788a6.1776595131.git.daniel@makrotopia.org> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <58aff8b5b1d691872342a6ffd3315f27854788a6.1776595131.git.daniel@makrotopia.org> On Sun, Apr 19, 2026 at 11:43:05AM +0100, Daniel Golle wrote: > The .get_stats64 callback runs in atomic context, but on > MDIO-connected switches every register read acquires the MDIO bus > mutex, which can sleep: > [ 12.645973] BUG: sleeping function called from invalid context at kernel/locking/mutex.c:609 > [ 12.654442] in_atomic(): 0, irqs_disabled(): 0, non_block: 0, pid: 759, name: grep > [ 12.663377] preempt_count: 0, expected: 0 > [ 12.667410] RCU nest depth: 1, expected: 0 > [ 12.671511] INFO: lockdep is turned off. > [ 12.675441] CPU: 0 UID: 0 PID: 759 Comm: grep Tainted: G S W 7.0.0+ #0 PREEMPT > [ 12.675453] Tainted: [S]=CPU_OUT_OF_SPEC, [W]=WARN > [ 12.675456] Hardware name: Bananapi BPI-R64 (DT) > [ 12.675459] Call trace: > [ 12.675462] show_stack+0x14/0x1c (C) > [ 12.675477] dump_stack_lvl+0x68/0x8c > [ 12.675487] dump_stack+0x14/0x1c > [ 12.675495] __might_resched+0x14c/0x220 > [ 12.675504] __might_sleep+0x44/0x80 > [ 12.675511] __mutex_lock+0x50/0xb10 > [ 12.675523] mutex_lock_nested+0x20/0x30 > [ 12.675532] mt7530_get_stats64+0x40/0x2ac > [ 12.675542] dsa_user_get_stats64+0x2c/0x40 > [ 12.675553] dev_get_stats+0x44/0x1e0 > [ 12.675564] dev_seq_printf_stats+0x24/0xe0 > [ 12.675575] dev_seq_show+0x14/0x3c > [ 12.675583] seq_read_iter+0x37c/0x480 > [ 12.675595] seq_read+0xd0/0xec > [ 12.675605] proc_reg_read+0x94/0xe4 > [ 12.675615] vfs_read+0x98/0x29c > [ 12.675625] ksys_read+0x54/0xdc > [ 12.675633] __arm64_sys_read+0x18/0x20 > [ 12.675642] invoke_syscall.constprop.0+0x54/0xec > [ 12.675653] do_el0_svc+0x3c/0xb4 > [ 12.675662] el0_svc+0x38/0x200 > [ 12.675670] el0t_64_sync_handler+0x98/0xdc > [ 12.675679] el0t_64_sync+0x158/0x15c > > For MDIO-connected switches, poll MIB counters asynchronously using a > delayed workqueue every second and let .get_stats64 return the cached > values under a spinlock. A mod_delayed_work() call on each read > triggers an immediate refresh so counters stay responsive when queried > more frequently. > > MMIO-connected switches (MT7988, EN7581, AN7583) are not affected > because their regmap does not sleep, so they continue to read MIB > counters directly in .get_stats64. > > Fixes: 88c810f35ed5 ("net: dsa: mt7530: implement .get_stats64") > Signed-off-by: Daniel Golle > Acked-by: Chester A. Unal > Reviewed-by: Andrew Lunn > --- > v2: > * use spin_lock_bh()/spin_unlock_bh() to prevent potential deadlock > * rate-limit mod_delayed_work() refresh to at most once per 100ms > * move cancel_delayed_work_sync() after dsa_unregister_switch() > * add mt753x_teardown() callback to cancel the stats work > * fix commit message FWIIW, I looked over the feedback generated by Sashiko for this patch, and I believe the issues it flags are false positives.