From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qk1-f197.google.com (mail-qk1-f197.google.com [209.85.222.197]) by kanga.kvack.org (Postfix) with ESMTP id 830836B0648 for ; Thu, 8 Nov 2018 15:35:29 -0500 (EST) Received: by mail-qk1-f197.google.com with SMTP id 67so40526214qkj.18 for ; Thu, 08 Nov 2018 12:35:29 -0800 (PST) Received: from mx1.redhat.com (mx1.redhat.com. [209.132.183.28]) by mx.google.com with ESMTPS id w7si3537342qte.36.2018.11.08.12.35.28 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 08 Nov 2018 12:35:28 -0800 (PST) From: Waiman Long Subject: [RFC PATCH 00/12] locking/lockdep: Add a new class of terminal locks Date: Thu, 8 Nov 2018 15:34:16 -0500 Message-Id: <1541709268-3766-1-git-send-email-longman@redhat.com> Sender: owner-linux-mm@kvack.org List-ID: To: Peter Zijlstra , Ingo Molnar , Will Deacon , Thomas Gleixner Cc: linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com, linux-mm@kvack.org, Petr Mladek , Sergey Senozhatsky , Andrey Ryabinin , Tejun Heo , Andrew Morton , Waiman Long The purpose of this patchset is to add a new class of locks called terminal locks and converts some of the low level raw or regular spinlocks to terminal locks. A terminal lock does not have forward dependency and it won't allow a lock or unlock operation on another lock. Two level nesting of terminal locks is allowed, though. Only spinlocks that are acquired with the _irq/_irqsave variants or acquired in an IRQ disabled context should be classified as terminal locks. Because of the restrictions on terminal locks, we can do simple checks on them without using the lockdep lock validation machinery. The advantages of making these changes are as follows: 1) The lockdep check will be faster for terminal locks without using the lock validation code. 2) It saves table entries used by the validation code and hence make it harder to overflow those tables. In fact, it is possible to overflow some of the tables by running a variety of different workloads on a debug kernel. I have seen bug reports about exhausting MAX_LOCKDEP_KEYS, MAX_LOCKDEP_ENTRIES and MAX_STACK_TRACE_ENTRIES. This patch will help to reduce the chance of overflowing some of the tables. Performance wise, there was no statistically significant difference in performanace when doing a parallel kernel build on a debug kernel. Below were selected output lines from the lockdep_stats files of the patched and unpatched kernels after bootup and running parallel kernel builds. Item Unpatched kernel Patched kernel % Change ---- ---------------- -------------- -------- direct dependencies 9732 8994 -7.6% dependency chains 18776 17033 -9.3% dependency chain hlocks 76044 68419 -10.0% stack-trace entries 110403 104341 -5.5% There were some reductions in the size of the lockdep tables. They were not significant, but it is still a good start to rein in the number of entries in those tables to make it harder to overflow them. Waiman Long (12): locking/lockdep: Rework lockdep_set_novalidate_class() locking/lockdep: Add a new terminal lock type locking/lockdep: Add DEFINE_TERMINAL_SPINLOCK() and related macros printk: Make logbuf_lock a terminal lock debugobjects: Mark pool_lock as a terminal lock debugobjects: Move printk out of db lock critical sections locking/lockdep: Add support for nested terminal locks debugobjects: Make object hash locks nested terminal locks lib/stackdepot: Make depot_lock a terminal spinlock locking/rwsem: Mark rwsem.wait_lock as a terminal lock cgroup: Mark the rstat percpu lock as terminal mm/kasan: Make quarantine_lock a terminal lock include/linux/lockdep.h | 34 +++++++++++++++--- include/linux/rwsem.h | 11 +++++- include/linux/spinlock_types.h | 34 ++++++++++++------ kernel/cgroup/rstat.c | 9 +++-- kernel/locking/lockdep.c | 67 ++++++++++++++++++++++++++++++------ kernel/locking/lockdep_internals.h | 5 +++ kernel/locking/lockdep_proc.c | 11 ++++-- kernel/locking/rwsem-xadd.c | 1 + kernel/printk/printk.c | 2 +- kernel/printk/printk_safe.c | 2 +- lib/debugobjects.c | 70 ++++++++++++++++++++++++++------------ lib/stackdepot.c | 2 +- mm/kasan/quarantine.c | 2 +- 13 files changed, 195 insertions(+), 55 deletions(-) -- 1.8.3.1