From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qk1-f199.google.com (mail-qk1-f199.google.com [209.85.222.199]) by kanga.kvack.org (Postfix) with ESMTP id 6CDE76B065C for ; Thu, 8 Nov 2018 15:36:31 -0500 (EST) Received: by mail-qk1-f199.google.com with SMTP id c84so41390491qkb.13 for ; Thu, 08 Nov 2018 12:36:31 -0800 (PST) Received: from mx1.redhat.com (mx1.redhat.com. [209.132.183.28]) by mx.google.com with ESMTPS id r32si4211709qvc.136.2018.11.08.12.36.30 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 08 Nov 2018 12:36:30 -0800 (PST) From: Waiman Long Subject: [RFC PATCH 10/12] locking/rwsem: Mark rwsem.wait_lock as a terminal lock Date: Thu, 8 Nov 2018 15:34:26 -0500 Message-Id: <1541709268-3766-11-git-send-email-longman@redhat.com> In-Reply-To: <1541709268-3766-1-git-send-email-longman@redhat.com> References: <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 wait_lock in a rwsem is always acquired with IRQ disabled. For the rwsem-xadd.c implementation, no other lock will be called while holding the wait_lock. So it satisfies the condition of being a terminal lock. By marking it as terminal, the lockdep overhead will be reduced. Signed-off-by: Waiman Long --- include/linux/rwsem.h | 11 ++++++++++- kernel/locking/rwsem-xadd.c | 1 + 2 files changed, 11 insertions(+), 1 deletion(-) diff --git a/include/linux/rwsem.h b/include/linux/rwsem.h index 67dbb57..a2a2385 100644 --- a/include/linux/rwsem.h +++ b/include/linux/rwsem.h @@ -77,16 +77,25 @@ static inline int rwsem_is_locked(struct rw_semaphore *sem) # define __RWSEM_DEP_MAP_INIT(lockname) #endif +/* + * The wait_lock is marked as a terminal lock to reduce lockdep overhead + * when the rwsem-xadd.c is used. This is implied when + * CONFIG_RWSEM_SPIN_ON_OWNER is true. The rwsem-spinlock.c implementation + * allows calling wake_up_process() while holding the wait_lock. So it + * can't be marked as terminal in this case. + */ #ifdef CONFIG_RWSEM_SPIN_ON_OWNER #define __RWSEM_OPT_INIT(lockname) , .osq = OSQ_LOCK_UNLOCKED, .owner = NULL +#define __RWSEM_WAIT_LOCK_INIT(x) __RAW_TERMINAL_SPIN_LOCK_UNLOCKED(x) #else #define __RWSEM_OPT_INIT(lockname) +#define __RWSEM_WAIT_LOCK_INIT(x) __RAW_SPIN_LOCK_UNLOCKED(x) #endif #define __RWSEM_INITIALIZER(name) \ { __RWSEM_INIT_COUNT(name), \ .wait_list = LIST_HEAD_INIT((name).wait_list), \ - .wait_lock = __RAW_SPIN_LOCK_UNLOCKED(name.wait_lock) \ + .wait_lock = __RWSEM_WAIT_LOCK_INIT(name.wait_lock) \ __RWSEM_OPT_INIT(name) \ __RWSEM_DEP_MAP_INIT(name) } diff --git a/kernel/locking/rwsem-xadd.c b/kernel/locking/rwsem-xadd.c index 09b1800..3dbe593 100644 --- a/kernel/locking/rwsem-xadd.c +++ b/kernel/locking/rwsem-xadd.c @@ -85,6 +85,7 @@ void __init_rwsem(struct rw_semaphore *sem, const char *name, #endif atomic_long_set(&sem->count, RWSEM_UNLOCKED_VALUE); raw_spin_lock_init(&sem->wait_lock); + lockdep_set_terminal_class(&sem->wait_lock); INIT_LIST_HEAD(&sem->wait_list); #ifdef CONFIG_RWSEM_SPIN_ON_OWNER sem->owner = NULL; -- 1.8.3.1