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/

1 files changed, 5 insertions, 1 deletions

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index c6d0c1dc6253..969736b33185 100644
--- 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);