lockdep: Add lockdep_assert_not_held()

Some kernel functions must be called without holding a specific lock.
Add lockdep_assert_not_held() to be used in these functions to detect
incorrect calls while holding a lock.

lockdep_assert_not_held() provides the opposite functionality of
lockdep_assert_held() which is used to assert calls that require
holding a specific lock.

Incorporates suggestions from Peter Zijlstra to avoid misfires when
lockdep_off() is employed.

The need for lockdep_assert_not_held() came up in a discussion on
ath10k patch. ath10k_drain_tx() and i915_vma_pin_ww() are examples
of functions that can use lockdep_assert_not_held().

Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/linux-wireless/871rdmu9z9.fsf@codeaurora.org/

diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
index 7b7ebf2..dbd9ea8 100644 (file)
--- a/include/linux/lockdep.h
+++ b/include/linux/lockdep.h
@@ -301,8 +301,12 @@ extern void lock_unpin_lock(struct lockdep_map *lock, struct pin_cookie);
 
 #define lockdep_depth(tsk)     (debug_locks ? (tsk)->lockdep_depth : 0)
 
-#define lockdep_assert_held(l) do {                            \
-               WARN_ON(debug_locks && !lockdep_is_held(l));    \
+#define lockdep_assert_held(l) do {                                    \
+               WARN_ON(debug_locks && lockdep_is_held(l) == 0);        \
+       } while (0)
+
+#define lockdep_assert_not_held(l)     do {                            \
+               WARN_ON(debug_locks && lockdep_is_held(l) == 1);        \
        } while (0)
 
 #define lockdep_assert_held_write(l)   do {                    \
@@ -393,7 +397,8 @@ extern int lockdep_is_held(const void *);
 #define lockdep_is_held_type(l, r)             (1)
 
 #define lockdep_assert_held(l)                 do { (void)(l); } while (0)
-#define lockdep_assert_held_write(l)   do { (void)(l); } while (0)
+#define lockdep_assert_not_held(l)             do { (void)(l); } while (0)
+#define lockdep_assert_held_write(l)           do { (void)(l); } while (0)
 #define lockdep_assert_held_read(l)            do { (void)(l); } while (0)
 #define lockdep_assert_held_once(l)            do { (void)(l); } while (0)
 

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index c6d0c1d..969736b 100644 (file)
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -5539,8 +5539,12 @@ noinstr int lock_is_held_type(const struct lockdep_map *lock, int read)
        unsigned long flags;
        int ret = 0;
 
+       /*
+        * Avoid false negative lockdep_assert_held() and
+        * lockdep_assert_not_held().
+        */
        if (unlikely(!lockdep_enabled()))
-               return 1; /* avoid false negative lockdep_assert_held() */
+               return -1;
 
        raw_local_irq_save(flags);
        check_flags(flags);