[PATCH v2 17/17] locking/lockdep: Check raw/non-raw locking conflicts

Waiman Long
2018-11-19T18:57:51Z

A task holding a raw spinlock should not acquire a non-raw lock as that
will break PREEMPT_RT kernel. Checking is now added and a lockdep warning
will be printed if that happens.

Signed-off-by: Waiman Long <longman@redhat.com>
---
include/linux/lockdep.h | 6 ++++++
include/linux/spinlock_types.h | 4 ++--
kernel/locking/lockdep.c | 15 +++++++++++++--
kernel/locking/spinlock_debug.c | 1 +
4 files changed, 22 insertions(+), 4 deletions(-)

diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
index b9435fb..9a6fe0e 100644
--- a/include/linux/lockdep.h
+++ b/include/linux/lockdep.h
@@ -150,12 +150,15 @@ struct lock_class_stats {
* another lock within its critical section is not allowed.
* 3) LOCKDEP_FLAG_TERMINAL_NESTABLE: This is a terminal lock that can
* allow one more regular terminal lock to be nested underneath it.
+ * 4) LOCKDEP_FLAG_RAW: This is a raw spinlock. A task holding a raw
+ * spinlock should not acquire a non-raw lock.
*
* Only the least significant 4 bits of the flags will be copied to the
* held_lock structure.
*/
#define LOCKDEP_FLAG_TERMINAL (1 << 0)
#define LOCKDEP_FLAG_TERMINAL_NESTABLE (1 << 1)
+#define LOCKDEP_FLAG_RAW (1 << 2)
#define LOCKDEP_FLAG_NOVALIDATE (1 << 4)

#define LOCKDEP_HLOCK_FLAGS_MASK 0x0f
@@ -333,6 +336,8 @@ extern void lockdep_init_map(struct lockdep_map *lock, const char *name,
do { (lock)->dep_map.flags |= LOCKDEP_FLAG_TERMINAL; } while (0)
#define lockdep_set_terminal_nestable_class(lock) \
do { (lock)->dep_map.flags |= LOCKDEP_FLAG_TERMINAL_NESTABLE; } while (0)
+#define lockdep_set_raw_class(lock) \
+ do { (lock)->dep_map.flags |= LOCKDEP_FLAG_RAW; } while (0)

/*
* Compare locking classes
@@ -448,6 +453,7 @@ static inline void lockdep_on(void)
do { (void)(key); } while (0)
#define lockdep_set_subclass(lock, sub) do { } while (0)

+#define lockdep_set_raw_class(lock) do { } while (0)
#define lockdep_set_novalidate_class(lock) do { } while (0)
#define lockdep_set_terminal_class(lock) do { } while (0)
#define lockdep_set_terminal_nestable_class(lock) do { } while (0)
diff --git a/include/linux/spinlock_types.h b/include/linux/spinlock_types.h
index 6a8086e..1d2114b 100644
--- a/include/linux/spinlock_types.h
+++ b/include/linux/spinlock_types.h
@@ -55,11 +55,11 @@
SPIN_DEP_MAP_INIT(lockname, f) }

#define __RAW_SPIN_LOCK_UNLOCKED(lockname) \
- (raw_spinlock_t) __RAW_SPIN_LOCK_INITIALIZER(lockname, 0)
+ (raw_spinlock_t) __RAW_SPIN_LOCK_INITIALIZER(lockname, LOCKDEP_FLAG_RAW)

#define __RAW_TERMINAL_SPIN_LOCK_UNLOCKED(lockname) \
(raw_spinlock_t) __RAW_SPIN_LOCK_INITIALIZER(lockname, \
- LOCKDEP_FLAG_TERMINAL)
+ LOCKDEP_FLAG_TERMINAL|LOCKDEP_FLAG_RAW)

#define DEFINE_RAW_SPINLOCK(x) raw_spinlock_t x = __RAW_SPIN_LOCK_UNLOCKED(x)
#define DEFINE_RAW_TERMINAL_SPINLOCK(x) \
diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 5a853a6..efafd2d 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -3273,8 +3273,8 @@ static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass,
* one isn't a regular terminal lock.
*/
prev_type = hlock_is_terminal(hlock);
- if (DEBUG_LOCKS_WARN_ON((prev_type == LOCKDEP_FLAG_TERMINAL) ||
- ((prev_type == LOCKDEP_FLAG_TERMINAL_NESTABLE) &&
+ if (DEBUG_LOCKS_WARN_ON((prev_type & LOCKDEP_FLAG_TERMINAL) ||
+ ((prev_type & LOCKDEP_FLAG_TERMINAL_NESTABLE) &&
(flags_is_terminal(class->flags) !=
LOCKDEP_FLAG_TERMINAL)))) {
pr_warn("Terminal lock error: prev lock = %s, curr lock = %s\n",
@@ -3282,6 +3282,17 @@ static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass,
return 0;
}

+ /*
+ * A task holding a raw spinlock should not acquire another
+ * non-raw lock.
+ */
+ if (DEBUG_LOCKS_WARN_ON((prev_type & LOCKDEP_FLAG_RAW) &&
+ !(class->flags & LOCKDEP_FLAG_RAW))) {
+ pr_warn("Raw lock error: prev lock = %s, curr lock = %s\n",
+ hlock->instance->name, class->name);
+ return 0;
+ }
+
if (hlock->class_idx == class_idx && nest_lock) {
if (hlock->references) {
/*
diff --git a/kernel/locking/spinlock_debug.c b/kernel/locking/spinlock_debug.c
index 9aa0fcc..1794d47 100644
--- a/kernel/locking/spinlock_debug.c
+++ b/kernel/locking/spinlock_debug.c
@@ -22,6 +22,7 @@ void __raw_spin_lock_init(raw_spinlock_t *lock, const char *name,
*/
debug_check_no_locks_freed((void *)lock, sizeof(*lock));
lockdep_init_map(&lock->dep_map, name, key, 0);
+ lockdep_set_raw_class(lock);
#endif
lock->raw_lock = (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
lock->magic = SPINLOCK_MAGIC;
--
1.8.3.1