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=-8.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,USER_AGENT_GIT 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 52081C43381 for ; Mon, 18 Mar 2019 08:58:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1EAD320857 for ; Mon, 18 Mar 2019 08:58:47 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="quzza9Np" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727584AbfCRI6p (ORCPT ); Mon, 18 Mar 2019 04:58:45 -0400 Received: from mail-pg1-f196.google.com ([209.85.215.196]:35300 "EHLO mail-pg1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727522AbfCRI6e (ORCPT ); Mon, 18 Mar 2019 04:58:34 -0400 Received: by mail-pg1-f196.google.com with SMTP id g8so261686pgf.2 for ; Mon, 18 Mar 2019 01:58:33 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id:in-reply-to:references; bh=8o6gy3jUrTIKg4DHxyQ/Y6z8fUbsl5WG4SDEUCkkek4=; b=quzza9Np9FTKQ8nXkeunTVXm7hA9pVQ/zXUnjaecnR/YjBlkoxJgir8oRrtVk5zjt7 FuTDrPeCng9AInAiNbaGM5UDTT34gqXgPWNlI/Tv9NswaAksCclf7wUwB594iBPprbxc kMNJ0M+V5IlIK4uTbMVD3s4SdoqYujh3cT0OVTYCgzKAry+FX8AMOP/RIKkyTX6iIfvl Z7qjTJJs4JL75UI/8I0kxcS5/h7SW7tCATDLSx2Q62G0C2z8nK2EZDitnq1yk9sLaGGx nq11Ksq62QBjRTjvmZ3lqfjcKVboKpnY1TEHNmKhcX5TM4Y4lN0HelatxMe3hMqSNatQ s2wA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references; bh=8o6gy3jUrTIKg4DHxyQ/Y6z8fUbsl5WG4SDEUCkkek4=; b=awSSNukImGytdXJTyzbFW7o2hWWfEkUeLq3J/zqVbB7jhaNScU7Knktqy/2pszTluS qwrJlIGazuvvWX+/fBzdTUaf9swuZWDM0gPy4Qbk9oV2B2o9OXsgzcHg+Rc70ulN22Yp 3xzrJnfj1BksRAh8FKg0zyTMWVxJIqSaP4Dp0miGYyKjw56tqQOyYTcrx7KBiYWJjU6t QqmTcJiM0GJ+eq9jjIeoj6eCcX9lhG3RqZate+7mAetivL7ZVpBDMyO/0IpIj0g3xNVA yts42OIEnUJLHywseQlaNWao+BSal6427FdtzTSXHKmL45Cp6NCX8obzOf2KPU3/R8KV CF0Q== X-Gm-Message-State: APjAAAX6MBbhPODdL23H8wfnp9dUPDqXT8dMhlIbhRxCoZiis9Awgsha dVuoXdAE5+WaTDzxCf/FOXHlpSpIVMQFaw== X-Google-Smtp-Source: APXvYqxMl+hu95A+n+LCU5a3RQk4/sUKg4Mg9bZZAYKxYKIKBrowhwE/daHCwegPCxK1GxlfCbKjhA== X-Received: by 2002:a17:902:2aca:: with SMTP id j68mr18170911plb.233.1552899513631; Mon, 18 Mar 2019 01:58:33 -0700 (PDT) Received: from localhost.localdomain ([203.100.54.194]) by smtp.gmail.com with ESMTPSA id k8sm11147024pgq.37.2019.03.18.01.58.31 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 18 Mar 2019 01:58:33 -0700 (PDT) From: Yuyang Du To: peterz@infradead.org, will.deacon@arm.com, mingo@kernel.org Cc: bvanassche@acm.org, ming.lei@redhat.com, linux-kernel@vger.kernel.org, Yuyang Du Subject: [PATCH v2 18/19] locking/lockdep: Update comments on dependency search Date: Mon, 18 Mar 2019 16:57:32 +0800 Message-Id: <20190318085733.3143-19-duyuyang@gmail.com> X-Mailer: git-send-email 2.17.2 (Apple Git-113) In-Reply-To: <20190318085733.3143-1-duyuyang@gmail.com> References: <20190318085733.3143-1-duyuyang@gmail.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The breadth-first search is implemented as flat-out non-recursive now, but the comments are still describing it as recursive, update the comments in that regard. Signed-off-by: Yuyang Du --- kernel/locking/lockdep.c | 21 ++++++++++----------- 1 file changed, 10 insertions(+), 11 deletions(-) diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c index 90d58cc..1d38bf6 100644 --- a/kernel/locking/lockdep.c +++ b/kernel/locking/lockdep.c @@ -1384,6 +1384,10 @@ static inline struct list_head *get_backward_dep(struct lock_list * lock) return &lock->class->locks_before; } +/* + * Forward- or backward-dependency search, used for both circular dependency + * checking and hardirq-unsafe/softirq-unsafe checking. + */ static int __bfs(struct lock_list *source_entry, void *data, int (*match)(struct lock_list *entry, void *data), @@ -1461,12 +1465,6 @@ static inline int __bfs_backwards(struct lock_list *src_entry, void *data, } /* - * Recursive, forwards-direction lock-dependency checking, used for - * both noncyclic checking and for hardirq-unsafe/softirq-unsafe - * checking. - */ - -/* * Print a dependency chain entry (this is only done when a deadlock * has been detected): */ @@ -2166,7 +2164,7 @@ static void print_deadlock_scenario(struct held_lock *nxt, /* * There was a chain-cache miss, and we are about to add a new dependency - * to a previous lock. We recursively validate the following rules: + * to a previous lock. We validate the following rules: * * - would the adding of the -> dependency create a * circular dependency in the graph? [== circular deadlock] @@ -2216,11 +2214,12 @@ static void print_deadlock_scenario(struct held_lock *nxt, /* * Prove that the new -> dependency would not * create a circular dependency in the graph. (We do this by - * forward-recursing into the graph starting at , and - * checking whether we can reach .) + * a breadth-first search into the graph starting at , + * which checks whether we can reach .) * - * We are using global variables to control the recursion, to - * keep the stackframe size of the recursive functions low: + * The search is limited by the size of the circular queue (i.e., + * MAX_CIRCULAR_QUEUE_SIZE) which keeps track of a breadth of nodes + * in the graph whose neighbours are to be checked. */ this.class = hlock_class(next); this.parent = NULL; -- 1.8.3.1