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Message-ID: <tip-fce45cd41101f1a9620267146b21f09b3454d8db@git.kernel.org>
Date: Tue, 6 Aug 2019 06:05:05 -0700
From: tip-bot for Davidlohr Bueso <tipbot@...or.com>
To: linux-tip-commits@...r.kernel.org
Cc: hpa@...or.com, dave@...olabs.net, linux-kernel@...r.kernel.org,
mingo@...nel.org, longman@...hat.com, tglx@...utronix.de,
peterz@...radead.org, dbueso@...e.de
Subject: [tip:locking/core] locking/rwsem: Check for operations on an
uninitialized rwsem
Commit-ID: fce45cd41101f1a9620267146b21f09b3454d8db
Gitweb: https://git.kernel.org/tip/fce45cd41101f1a9620267146b21f09b3454d8db
Author: Davidlohr Bueso <dave@...olabs.net>
AuthorDate: Sun, 28 Jul 2019 21:47:35 -0700
Committer: Peter Zijlstra <peterz@...radead.org>
CommitDate: Tue, 6 Aug 2019 12:49:15 +0200
locking/rwsem: Check for operations on an uninitialized rwsem
Currently rwsems is the only locking primitive that lacks this
debug feature. Add it under CONFIG_DEBUG_RWSEMS and do the magic
checking in the locking fastpath (trylock) operation such that
we cover all cases. The unlocking part is pretty straightforward.
Signed-off-by: Davidlohr Bueso <dbueso@...e.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Acked-by: Waiman Long <longman@...hat.com>
Cc: mingo@...nel.org
Cc: Davidlohr Bueso <dave@...olabs.net>
Link: https://lkml.kernel.org/r/20190729044735.9632-1-dave@stgolabs.net
---
include/linux/rwsem.h | 10 ++++++++++
kernel/locking/rwsem.c | 22 ++++++++++++++++++----
2 files changed, 28 insertions(+), 4 deletions(-)
diff --git a/include/linux/rwsem.h b/include/linux/rwsem.h
index 9d9c663987d8..00d6054687dd 100644
--- a/include/linux/rwsem.h
+++ b/include/linux/rwsem.h
@@ -45,6 +45,9 @@ struct rw_semaphore {
#endif
raw_spinlock_t wait_lock;
struct list_head wait_list;
+#ifdef CONFIG_DEBUG_RWSEMS
+ void *magic;
+#endif
#ifdef CONFIG_DEBUG_LOCK_ALLOC
struct lockdep_map dep_map;
#endif
@@ -73,6 +76,12 @@ static inline int rwsem_is_locked(struct rw_semaphore *sem)
# define __RWSEM_DEP_MAP_INIT(lockname)
#endif
+#ifdef CONFIG_DEBUG_RWSEMS
+# define __DEBUG_RWSEM_INITIALIZER(lockname) , .magic = &lockname
+#else
+# define __DEBUG_RWSEM_INITIALIZER(lockname)
+#endif
+
#ifdef CONFIG_RWSEM_SPIN_ON_OWNER
#define __RWSEM_OPT_INIT(lockname) , .osq = OSQ_LOCK_UNLOCKED
#else
@@ -85,6 +94,7 @@ static inline int rwsem_is_locked(struct rw_semaphore *sem)
.wait_list = LIST_HEAD_INIT((name).wait_list), \
.wait_lock = __RAW_SPIN_LOCK_UNLOCKED(name.wait_lock) \
__RWSEM_OPT_INIT(name) \
+ __DEBUG_RWSEM_INITIALIZER(name) \
__RWSEM_DEP_MAP_INIT(name) }
#define DECLARE_RWSEM(name) \
diff --git a/kernel/locking/rwsem.c b/kernel/locking/rwsem.c
index 354238a08b7a..eef04551eae7 100644
--- a/kernel/locking/rwsem.c
+++ b/kernel/locking/rwsem.c
@@ -105,8 +105,9 @@
#ifdef CONFIG_DEBUG_RWSEMS
# define DEBUG_RWSEMS_WARN_ON(c, sem) do { \
if (!debug_locks_silent && \
- WARN_ONCE(c, "DEBUG_RWSEMS_WARN_ON(%s): count = 0x%lx, owner = 0x%lx, curr 0x%lx, list %sempty\n",\
+ WARN_ONCE(c, "DEBUG_RWSEMS_WARN_ON(%s): count = 0x%lx, magic = 0x%lx, owner = 0x%lx, curr 0x%lx, list %sempty\n",\
#c, atomic_long_read(&(sem)->count), \
+ (unsigned long) sem->magic, \
atomic_long_read(&(sem)->owner), (long)current, \
list_empty(&(sem)->wait_list) ? "" : "not ")) \
debug_locks_off(); \
@@ -329,6 +330,9 @@ void __init_rwsem(struct rw_semaphore *sem, const char *name,
*/
debug_check_no_locks_freed((void *)sem, sizeof(*sem));
lockdep_init_map(&sem->dep_map, name, key, 0);
+#endif
+#ifdef CONFIG_DEBUG_RWSEMS
+ sem->magic = sem;
#endif
atomic_long_set(&sem->count, RWSEM_UNLOCKED_VALUE);
raw_spin_lock_init(&sem->wait_lock);
@@ -1358,11 +1362,14 @@ static inline int __down_read_killable(struct rw_semaphore *sem)
static inline int __down_read_trylock(struct rw_semaphore *sem)
{
+ long tmp;
+
+ DEBUG_RWSEMS_WARN_ON(sem->magic != sem, sem);
+
/*
* Optimize for the case when the rwsem is not locked at all.
*/
- long tmp = RWSEM_UNLOCKED_VALUE;
-
+ tmp = RWSEM_UNLOCKED_VALUE;
do {
if (atomic_long_try_cmpxchg_acquire(&sem->count, &tmp,
tmp + RWSEM_READER_BIAS)) {
@@ -1403,8 +1410,11 @@ static inline int __down_write_killable(struct rw_semaphore *sem)
static inline int __down_write_trylock(struct rw_semaphore *sem)
{
- long tmp = RWSEM_UNLOCKED_VALUE;
+ long tmp;
+ DEBUG_RWSEMS_WARN_ON(sem->magic != sem, sem);
+
+ tmp = RWSEM_UNLOCKED_VALUE;
if (atomic_long_try_cmpxchg_acquire(&sem->count, &tmp,
RWSEM_WRITER_LOCKED)) {
rwsem_set_owner(sem);
@@ -1420,7 +1430,9 @@ inline void __up_read(struct rw_semaphore *sem)
{
long tmp;
+ DEBUG_RWSEMS_WARN_ON(sem->magic != sem, sem);
DEBUG_RWSEMS_WARN_ON(!is_rwsem_reader_owned(sem), sem);
+
rwsem_clear_reader_owned(sem);
tmp = atomic_long_add_return_release(-RWSEM_READER_BIAS, &sem->count);
DEBUG_RWSEMS_WARN_ON(tmp < 0, sem);
@@ -1438,12 +1450,14 @@ static inline void __up_write(struct rw_semaphore *sem)
{
long tmp;
+ DEBUG_RWSEMS_WARN_ON(sem->magic != sem, sem);
/*
* sem->owner may differ from current if the ownership is transferred
* to an anonymous writer by setting the RWSEM_NONSPINNABLE bits.
*/
DEBUG_RWSEMS_WARN_ON((rwsem_owner(sem) != current) &&
!rwsem_test_oflags(sem, RWSEM_NONSPINNABLE), sem);
+
rwsem_clear_owner(sem);
tmp = atomic_long_fetch_add_release(-RWSEM_WRITER_LOCKED, &sem->count);
if (unlikely(tmp & RWSEM_FLAG_WAITERS))
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