From 5149cbac4235e12a34cf089592a8bd1c9fcfa467 Mon Sep 17 00:00:00 2001
From: Waiman Long <longman@redhat.com>
Date: Fri, 30 Mar 2018 17:27:58 -0400
Subject: [PATCH] locking/rwsem: Add DEBUG_RWSEMS to look for lock/unlock
mismatches
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 <longman@redhat.com>
Acked-by: Davidlohr Bueso <dave@stgolabs.net>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1522445280-7767-2-git-send-email-longman@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
kernel/locking/rwsem.c | 4 ++++
kernel/locking/rwsem.h | 8 +++++++-
lib/Kconfig.debug | 8 ++++++++
3 files changed, 19 insertions(+), 1 deletion(-)
diff --git a/kernel/locking/rwsem.c b/kernel/locking/rwsem.c
index f549c552dbf1e..30465a2f2b6cf 100644
--- a/kernel/locking/rwsem.c
+++ b/kernel/locking/rwsem.c
@@ -117,6 +117,7 @@ EXPORT_SYMBOL(down_write_trylock);
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 @@ EXPORT_SYMBOL(up_read);
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 @@ EXPORT_SYMBOL(up_write);
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 @@ EXPORT_SYMBOL(down_write_killable_nested);
void up_read_non_owner(struct rw_semaphore *sem)
{
+ DEBUG_RWSEMS_WARN_ON(sem->owner != RWSEM_READER_OWNED);
__up_read(sem);
}
diff --git a/kernel/locking/rwsem.h b/kernel/locking/rwsem.h
index a883b8f1fdc6e..a17cba8d94bb1 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 64155e310a9f2..88650ab5cedb2 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 debugging 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
@@ -1097,6 +1104,7 @@ config PROVE_LOCKING
select DEBUG_SPINLOCK
select DEBUG_MUTEXES
select DEBUG_RT_MUTEXES if RT_MUTEXES
+ select DEBUG_RWSEMS if RWSEM_SPIN_ON_OWNER
select DEBUG_LOCK_ALLOC
select TRACE_IRQFLAGS
default n
--
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