From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752125AbeCZTLa (ORCPT ); Mon, 26 Mar 2018 15:11:30 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:43846 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1750983AbeCZTL3 (ORCPT ); Mon, 26 Mar 2018 15:11:29 -0400 From: Waiman Long To: Ingo Molnar , Peter Zijlstra Cc: linux-kernel@vger.kernel.org, Waiman Long Subject: [PATCH] locking/rwsem: Add DEBUG_RWSEMS to look for lock/unlock mismatches Date: Mon, 26 Mar 2018 15:11:05 -0400 Message-Id: <1522091465-18102-1-git-send-email-longman@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org For a rwsem, locking can either be exclusive or shared. The corresponding exclusive or shared unlock must be used. Otherwise, the protected data structures may get corrupted or the lock may be in an inconsistent state. In order to detect such anomaly, a new configuration option DEBUG_RWSEMS is added which can be enabled to look for such mismatches and print warnings that that happens. Signed-off-by: Waiman Long --- kernel/locking/rwsem.c | 4 ++++ kernel/locking/rwsem.h | 8 +++++++- lib/Kconfig.debug | 7 +++++++ 3 files changed, 18 insertions(+), 1 deletion(-) diff --git a/kernel/locking/rwsem.c b/kernel/locking/rwsem.c index f549c55..58a0c12 100644 --- a/kernel/locking/rwsem.c +++ b/kernel/locking/rwsem.c @@ -117,6 +117,7 @@ int down_write_trylock(struct rw_semaphore *sem) void up_read(struct rw_semaphore *sem) { rwsem_release(&sem->dep_map, 1, _RET_IP_); + DEBUG_RWSEMS_WARN_ON(sem->owner != RWSEM_READER_OWNED); __up_read(sem); } @@ -129,6 +130,7 @@ void up_read(struct rw_semaphore *sem) void up_write(struct rw_semaphore *sem) { rwsem_release(&sem->dep_map, 1, _RET_IP_); + DEBUG_RWSEMS_WARN_ON(sem->owner != current); rwsem_clear_owner(sem); __up_write(sem); @@ -142,6 +144,7 @@ void up_write(struct rw_semaphore *sem) void downgrade_write(struct rw_semaphore *sem) { lock_downgrade(&sem->dep_map, _RET_IP_); + DEBUG_RWSEMS_WARN_ON(sem->owner != current); rwsem_set_reader_owned(sem); __downgrade_write(sem); @@ -211,6 +214,7 @@ int __sched down_write_killable_nested(struct rw_semaphore *sem, int subclass) void up_read_non_owner(struct rw_semaphore *sem) { + DEBUG_RWSEMS_WARN_ON(RWSEM_WRITER_OWNED(sem->owner)); __up_read(sem); } diff --git a/kernel/locking/rwsem.h b/kernel/locking/rwsem.h index a883b8f..563a7bc 100644 --- a/kernel/locking/rwsem.h +++ b/kernel/locking/rwsem.h @@ -16,6 +16,12 @@ */ #define RWSEM_READER_OWNED ((struct task_struct *)1UL) +#ifdef CONFIG_DEBUG_RWSEMS +#define DEBUG_RWSEMS_WARN_ON(c) DEBUG_LOCKS_WARN_ON(c) +#else +#define DEBUG_RWSEMS_WARN_ON(c) +#endif + #ifdef CONFIG_RWSEM_SPIN_ON_OWNER /* * All writes to owner are protected by WRITE_ONCE() to make sure that @@ -41,7 +47,7 @@ static inline void rwsem_set_reader_owned(struct rw_semaphore *sem) * do a write to the rwsem cacheline when it is really necessary * to minimize cacheline contention. */ - if (sem->owner != RWSEM_READER_OWNED) + if (READ_ONCE(sem->owner) != RWSEM_READER_OWNED) WRITE_ONCE(sem->owner, RWSEM_READER_OWNED); } diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug index 64155e3..0958192 100644 --- a/lib/Kconfig.debug +++ b/lib/Kconfig.debug @@ -1075,6 +1075,13 @@ config DEBUG_WW_MUTEX_SLOWPATH even a debug kernel. If you are a driver writer, enable it. If you are a distro, do not. +config DEBUG_RWSEMS + bool "RW Semaphore debugging: basic checks" + depends on DEBUG_KERNEL && RWSEM_SPIN_ON_OWNER + help + This feature allows mismatched rw semaphore locks and unlocks + to be detected and reported. + config DEBUG_LOCK_ALLOC bool "Lock debugging: detect incorrect freeing of live locks" depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT -- 1.8.3.1