From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from pidgin.makrotopia.org (pidgin.makrotopia.org [185.142.180.65]) (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 64F723101BC; Fri, 17 Apr 2026 12:08:45 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=185.142.180.65 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776427726; cv=none; b=W8pZpzaDjXQq9Pnpb1uFhwYAW0eMgXbWmFSBVV0oSS7xjtE1VdOg8ZSsBvTn5KCODEAaORU2CPx9xwK1D6Dj2brFmmkcnuPv/kTnisYP/fO+HV2rrD/yPbIxWExdnLosoyaD0N57znI8+POVvOWYkcucAn/pbvGEBsLSmzxStOc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776427726; c=relaxed/simple; bh=Fu7cBTVm4EUD/2LDczIxEyrLvsmxg0Mr0T2osrZ0MyI=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=Wce1yNdBqXAxgEh6ciSsiFgFTTyWF76ZMEBQL6MMcG2NT+JLdBko5iHLMM03UvgA6Ww/YIVUJsDAuqKUCHGGClHlJtwpHEs+M1r0qsTTdgK6EFTKK/pQt5m513nzBl2kNhhQ8+z0FX1rifjRSmNiVnJIQOBruyXM8TuUd5tAEvU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=makrotopia.org; spf=pass smtp.mailfrom=makrotopia.org; arc=none smtp.client-ip=185.142.180.65 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=makrotopia.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=makrotopia.org Received: from local by pidgin.makrotopia.org with esmtpsa (TLS1.3:TLS_AES_256_GCM_SHA384:256) (Exim 4.99) (envelope-from ) id 1wDhzt-000000004Gm-0SZ7; Fri, 17 Apr 2026 12:08:33 +0000 Date: Fri, 17 Apr 2026 13:08:29 +0100 From: Daniel Golle To: "Chester A. Unal" Cc: 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] net: dsa: mt7530: fix .get_stats64 sleeping in atomic context Message-ID: References: <79dc0ec5b6be698b14cb66339d6f63033ca2934a.1776397542.git.daniel@makrotopia.org> Precedence: bulk X-Mailing-List: linux-kernel@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: On Fri, Apr 17, 2026 at 07:35:46AM +0000, Chester A. Unal wrote: > On 17 April 2026 04:55:57 WEST, 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 per-port spinlock. A mod_delayed_work() call on each ^^^^^^^^^^^^^^^^^^^ Just noticed I forgot to update the commit message when changing the implementation to use a single shared spinlock for all ports... I'll send v2 tomorrow fixing that, and what ever else comes up, if anything. > >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 > >--- > >This bug highlights a bigger problem and the actual cause: > >Locking in the mt7530 driver deserves a cleanup, and refactoring > >towards cleanly and directly using the regmap API. > >I've prepared this already and am going to submit a series doing > >most of that using Coccinelle semantic patches once net-next opens > >again. > > Acked-by: Chester A. Unal > > Chester A.