Commit 3e31f947 authored by Shuah Khan's avatar Shuah Khan Committed by Ingo Molnar
Browse files

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: default avatarShuah Khan <skhan@linuxfoundation.org>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/linux-wireless/871rdmu9z9.fsf@codeaurora.org/
parent 864b4355

include/linux/lockdep.h

+8 −3
Original line number Diff line number Diff line
@@ -302,7 +302,11 @@ 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));	\

		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 {			\
@@ -393,6 +397,7 @@ 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_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)

kernel/locking/lockdep.c

+5 −1
Original line number Diff line number Diff line
@@ -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);