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 X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 37BD6C6778F for ; Wed, 25 Jul 2018 14:20:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E9DC920843 for ; Wed, 25 Jul 2018 14:20:12 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E9DC920843 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=zytor.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729202AbeGYPcA (ORCPT ); Wed, 25 Jul 2018 11:32:00 -0400 Received: from terminus.zytor.com ([198.137.202.136]:39813 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728649AbeGYPb7 (ORCPT ); Wed, 25 Jul 2018 11:31:59 -0400 Received: from terminus.zytor.com (localhost [127.0.0.1]) by terminus.zytor.com (8.15.2/8.15.2) with ESMTPS id w6PEJY3M399808 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NO); Wed, 25 Jul 2018 07:19:34 -0700 Received: (from tipbot@localhost) by terminus.zytor.com (8.15.2/8.15.2/Submit) id w6PEJYPR399805; Wed, 25 Jul 2018 07:19:34 -0700 Date: Wed, 25 Jul 2018 07:19:34 -0700 X-Authentication-Warning: terminus.zytor.com: tipbot set sender to tipbot@zytor.com using -f From: tip-bot for Peter Rosin Message-ID: Cc: will.deacon@arm.com, torvalds@linux-foundation.org, hpa@zytor.com, tglx@linutronix.de, jsperbeck@google.com, wsa@the-dreams.de, linux-kernel@vger.kernel.org, mingo@kernel.org, dave@stgolabs.net, dpf@google.com, pombredanne@nexb.com, peda@axentia.se, peterz@infradead.org, gregkh@linuxfoundation.org, deepadinamani@google.com Reply-To: tglx@linutronix.de, jsperbeck@google.com, linux-kernel@vger.kernel.org, wsa@the-dreams.de, mingo@kernel.org, dave@stgolabs.net, peda@axentia.se, dpf@google.com, pombredanne@nexb.com, deepadinamani@google.com, peterz@infradead.org, gregkh@linuxfoundation.org, will.deacon@arm.com, torvalds@linux-foundation.org, hpa@zytor.com In-Reply-To: <20180720083914.1950-3-peda@axentia.se> References: <20180720083914.1950-3-peda@axentia.se> To: linux-tip-commits@vger.kernel.org Subject: [tip:locking/urgent] i2c/mux, locking/core: Annotate the nested rt_mutex usage Git-Commit-ID: 7b94ea50514d1a0dc94f02723b603c27bc0ea597 X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: 7b94ea50514d1a0dc94f02723b603c27bc0ea597 Gitweb: https://git.kernel.org/tip/7b94ea50514d1a0dc94f02723b603c27bc0ea597 Author: Peter Rosin AuthorDate: Fri, 20 Jul 2018 10:39:14 +0200 Committer: Ingo Molnar CommitDate: Wed, 25 Jul 2018 11:22:20 +0200 i2c/mux, locking/core: Annotate the nested rt_mutex usage If an i2c topology has instances of nested muxes, then a lockdep splat is produced when when i2c_parent_lock_bus() is called. Here is an example: ============================================ WARNING: possible recursive locking detected -------------------------------------------- insmod/68159 is trying to acquire lock: (i2c_register_adapter#2){+.+.}, at: i2c_parent_lock_bus+0x32/0x50 [i2c_mux] but task is already holding lock: (i2c_register_adapter#2){+.+.}, at: i2c_parent_lock_bus+0x32/0x50 [i2c_mux] other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(i2c_register_adapter#2); lock(i2c_register_adapter#2); *** DEADLOCK *** May be due to missing lock nesting notation 1 lock held by insmod/68159: #0: (i2c_register_adapter#2){+.+.}, at: i2c_parent_lock_bus+0x32/0x50 [i2c_mux] stack backtrace: CPU: 13 PID: 68159 Comm: insmod Tainted: G O Call Trace: dump_stack+0x67/0x98 __lock_acquire+0x162e/0x1780 lock_acquire+0xba/0x200 rt_mutex_lock+0x44/0x60 i2c_parent_lock_bus+0x32/0x50 [i2c_mux] i2c_parent_lock_bus+0x3e/0x50 [i2c_mux] i2c_smbus_xfer+0xf0/0x700 i2c_smbus_read_byte+0x42/0x70 my2c_init+0xa2/0x1000 [my2c] do_one_initcall+0x51/0x192 do_init_module+0x62/0x216 load_module+0x20f9/0x2b50 SYSC_init_module+0x19a/0x1c0 SyS_init_module+0xe/0x10 do_syscall_64+0x6c/0x1a0 entry_SYSCALL_64_after_hwframe+0x42/0xb7 Reported-by: John Sperbeck Tested-by: John Sperbeck Signed-off-by: Peter Rosin Signed-off-by: Peter Zijlstra (Intel) Cc: Davidlohr Bueso Cc: Deepa Dinamani Cc: Greg Kroah-Hartman Cc: Linus Torvalds Cc: Peter Chang Cc: Peter Zijlstra Cc: Philippe Ombredanne Cc: Thomas Gleixner Cc: Will Deacon Cc: Wolfram Sang Link: http://lkml.kernel.org/r/20180720083914.1950-3-peda@axentia.se Signed-off-by: Ingo Molnar --- drivers/i2c/i2c-core-base.c | 2 +- drivers/i2c/i2c-mux.c | 4 ++-- 2 files changed, 3 insertions(+), 3 deletions(-) diff --git a/drivers/i2c/i2c-core-base.c b/drivers/i2c/i2c-core-base.c index 301285c54603..15c95aaa484c 100644 --- a/drivers/i2c/i2c-core-base.c +++ b/drivers/i2c/i2c-core-base.c @@ -624,7 +624,7 @@ static int i2c_check_addr_busy(struct i2c_adapter *adapter, int addr) static void i2c_adapter_lock_bus(struct i2c_adapter *adapter, unsigned int flags) { - rt_mutex_lock(&adapter->bus_lock); + rt_mutex_lock_nested(&adapter->bus_lock, i2c_adapter_depth(adapter)); } /** diff --git a/drivers/i2c/i2c-mux.c b/drivers/i2c/i2c-mux.c index 300ab4b672e4..29646aa6132e 100644 --- a/drivers/i2c/i2c-mux.c +++ b/drivers/i2c/i2c-mux.c @@ -144,7 +144,7 @@ static void i2c_mux_lock_bus(struct i2c_adapter *adapter, unsigned int flags) struct i2c_mux_priv *priv = adapter->algo_data; struct i2c_adapter *parent = priv->muxc->parent; - rt_mutex_lock(&parent->mux_lock); + rt_mutex_lock_nested(&parent->mux_lock, i2c_adapter_depth(adapter)); if (!(flags & I2C_LOCK_ROOT_ADAPTER)) return; i2c_lock_bus(parent, flags); @@ -181,7 +181,7 @@ static void i2c_parent_lock_bus(struct i2c_adapter *adapter, struct i2c_mux_priv *priv = adapter->algo_data; struct i2c_adapter *parent = priv->muxc->parent; - rt_mutex_lock(&parent->mux_lock); + rt_mutex_lock_nested(&parent->mux_lock, i2c_adapter_depth(adapter)); i2c_lock_bus(parent, flags); }