linux-kernel - [PATCH v3 07/35] lockdep: Annotate lockdep assertions for capability analysis

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Message-ID: <20250918140451.1289454-8-elver@google.com>
Date: Thu, 18 Sep 2025 15:59:18 +0200
From: Marco Elver <elver@...gle.com>
To: elver@...gle.com, Peter Zijlstra <peterz@...radead.org>, 
	Boqun Feng <boqun.feng@...il.com>, Ingo Molnar <mingo@...nel.org>, Will Deacon <will@...nel.org>
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	"Paul E. McKenney" <paulmck@...nel.org>, Alexander Potapenko <glider@...gle.com>, Arnd Bergmann <arnd@...db.de>, 
	Bart Van Assche <bvanassche@....org>, Bill Wendling <morbo@...gle.com>, Christoph Hellwig <hch@....de>, 
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Subject: [PATCH v3 07/35] lockdep: Annotate lockdep assertions for capability analysis

Clang's capability analysis can be made aware of functions that assert
that capabilities/locks are held.

Presence of these annotations causes the analysis to assume the
capability is held after calls to the annotated function, and avoid
false positives with complex control-flow; for example, where not all
control-flow paths in a function require a held lock, and therefore
marking the function with __must_hold(..) is inappropriate.

Signed-off-by: Marco Elver <elver@...gle.com>
---
v3:
* __assert -> __assume rename
---
 include/linux/lockdep.h | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
index 67964dc4db95..11b3d22555ff 100644
--- a/include/linux/lockdep.h
+++ b/include/linux/lockdep.h
@@ -282,16 +282,16 @@ extern void lock_unpin_lock(struct lockdep_map *lock, struct pin_cookie);
 	do { WARN_ON_ONCE(debug_locks && !(cond)); } while (0)
 
 #define lockdep_assert_held(l)		\
-	lockdep_assert(lockdep_is_held(l) != LOCK_STATE_NOT_HELD)
+	do { lockdep_assert(lockdep_is_held(l) != LOCK_STATE_NOT_HELD); __assume_cap(l); } while (0)
 
 #define lockdep_assert_not_held(l)	\
 	lockdep_assert(lockdep_is_held(l) != LOCK_STATE_HELD)
 
 #define lockdep_assert_held_write(l)	\
-	lockdep_assert(lockdep_is_held_type(l, 0))
+	do { lockdep_assert(lockdep_is_held_type(l, 0)); __assume_cap(l); } while (0)
 
 #define lockdep_assert_held_read(l)	\
-	lockdep_assert(lockdep_is_held_type(l, 1))
+	do { lockdep_assert(lockdep_is_held_type(l, 1)); __assume_shared_cap(l); } while (0)
 
 #define lockdep_assert_held_once(l)		\
 	lockdep_assert_once(lockdep_is_held(l) != LOCK_STATE_NOT_HELD)
@@ -389,10 +389,10 @@ extern int lockdep_is_held(const void *);
 #define lockdep_assert(c)			do { } while (0)
 #define lockdep_assert_once(c)			do { } while (0)
 
-#define lockdep_assert_held(l)			do { (void)(l); } while (0)
+#define lockdep_assert_held(l)			__assume_cap(l)
 #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_write(l)		__assume_cap(l)
+#define lockdep_assert_held_read(l)		__assume_shared_cap(l)
 #define lockdep_assert_held_once(l)		do { (void)(l); } while (0)
 #define lockdep_assert_none_held_once()	do { } while (0)
 
-- 
2.51.0.384.g4c02a37b29-goog