From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 81DC3F43695 for ; Fri, 17 Apr 2026 12:08:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=tjpGNp21pxfsQzkG2LPNFYZA2ZEfPjizwMSu6qyomN8=; b=3/DhpGtag2P3ODrTHr506tL5RD u0CGfmJRbP0ZXJ1GfcdpanVjf3p9OvwiMdDhE/LldlpYsSrIf3C4VncrqpmfR+zcODyP/pu1GbZVK q+uPse+5PcjsVZ+3Xllufw4TgUpaBT50n8oL0PMA9AKryUqPCOSrrnbOsIs7wZ9ADKOT47WSQXOQO DKayG/FPMIAHq9kjXwelA98PawP4LaCd/yW/psD2WR7PxPJ5e2ZRDtlzOChaSmqzt4yHKF9KKPYaq Yvsivioijy0GIIpkXtLtk+JtHt9JYldeoDxzPk2t5CM/kaMI6LVldbESvIo0NwStobm5Pdd2rT3jf H+JZxwNQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1wDi0A-000000041UO-2np3; Fri, 17 Apr 2026 12:08:50 +0000 Received: from pidgin.makrotopia.org ([2a07:2ec0:3002::65]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1wDi08-000000041Tn-4AZb; Fri, 17 Apr 2026 12:08:50 +0000 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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260417_050849_053660_2BD2EC84 X-CRM114-Status: GOOD ( 13.18 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org 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.