[tip: locking/core] lockdep: Add lockdep_assert_not_held()

* [tip: locking/core] lockdep: Add lockdep_assert_not_held()
@ 2021-03-06 11:54 tip-bot2 for Shuah Khan
  0 siblings, 0 replies; 2+ messages in thread
From: tip-bot2 for Shuah Khan @ 2021-03-06 11:54 UTC (permalink / raw)
  To: linux-tip-commits
  Cc: Shuah Khan, Peter Zijlstra (Intel), Ingo Molnar, x86, linux-kernel

The following commit has been merged into the locking/core branch of tip:

Commit-ID:     3e31f94752e454bdd0ca4a1d046ee21f80c166c5
Gitweb:        https://git.kernel.org/tip/3e31f94752e454bdd0ca4a1d046ee21f80c166c5
Author:        Shuah Khan <skhan@linuxfoundation.org>
AuthorDate:    Fri, 26 Feb 2021 17:06:58 -07:00
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Sat, 06 Mar 2021 12:51:05 +01:00

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/
---
 include/linux/lockdep.h  | 11 ++++++++---
 kernel/locking/lockdep.c |  6 +++++-
 2 files changed, 13 insertions(+), 4 deletions(-)

diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
index 7b7ebf2..dbd9ea8 100644
--- 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
--- 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);

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