From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752062AbdIFI2K (ORCPT ); Wed, 6 Sep 2017 04:28:10 -0400 Received: from mail-pf0-f180.google.com ([209.85.192.180]:36299 "EHLO mail-pf0-f180.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751824AbdIFI2E (ORCPT ); Wed, 6 Sep 2017 04:28:04 -0400 X-Google-Smtp-Source: ADKCNb4wBp0wYXMwVbmt/Dk0UQ/e5MiswKrpfCEHBjUgwMG+bHCPgyXuxYyiGKeuj23zaSXvNlfz8w== From: Boqun Feng To: linux-kernel@vger.kernel.org Cc: Ingo Molnar , Peter Zijlstra , Gautham R Shenoy , Byungchul Park , Boqun Feng Subject: [RFC tip/locking v2 00/13] lockdep: Support deadlock detection for recursive read locks Date: Wed, 6 Sep 2017 16:28:11 +0800 Message-Id: <20170906082824.16078-1-boqun.feng@gmail.com> X-Mailer: git-send-email 2.14.1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Ingo and Peter, This is V2 for recursive read lock support in lockdep. I fix several bugs in V1 and also add irq inversion detection support for recursive read locks. V1: https://marc.info/?l=linux-kernel&m=150393341825453 As Peter pointed out: https://marc.info/?l=linux-kernel&m=150349072023540 The lockdep current has a limit support for recursive read locks, the deadlock case as follow could not be detected: read_lock(A); lock(B); lock(B); write_lock(A); I got some inspiration from Gautham R Shenoy: https://lwn.net/Articles/332801/ , and came up with this series. The basic idea is: * Add recursive read locks into the graph * Classify dependencies into --(RR)-->, --(NR)-->, --(RN)-->, --(NN)-->, where R stands for recursive read lock, N stands for other locks(i.e. non-recursive read locks and write locks). * Define strong dependency paths as the paths of dependencies don't have two adjacent dependencies as --(*R)--> and --(R*)-->. * Extend __bfs() to only traverse on strong dependency paths. * If __bfs() finds a strong dependency circle, then a deadlock is reported. The whole series is based on current master branch of Linus' tree: e7d0c41ecc2e ("Merge tag 'devprop-4.14-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm") , and I also put it at: git://git.kernel.org/pub/scm/linux/kernel/git/boqun/linux.git arr-rfc-v2 The whole series consists of 13 patches: 1. Do a clean up on the return value of __bfs() and its friends. 2. Make __bfs() able to visit every dependency until a match is found. The old version of __bfs() could only visit each lock class once, and this is insufficient if we are going to add recursive read locks into the dependency graph. 3. Make lock state LOCK_*_READ stand for recursive read lock only and LOCK_* stand for write lock and non-recursive read lock. 4-5 Extend __bfs() to be able to traverse the stong dependency patchs after recursive read locks added into the graph. 6-8 Adjust check_redundant(), check_noncircular() and check_irq_usage() with recursive read locks into consideration. 9. Finally add recursive read locks into the dependency graph. 10-11 Adjust lock cache chain key generation with recursive read locks into consideration, and provide a test case. 12-13 Add more test cases. I did pass all the lockdep selftest cases(including those I introduce), and now run it on one of my box, haven't shot my feet yet. Test and comments are welcome! Regards, Boqun