On 2/6/25 10:10 AM, Marco Elver wrote:
diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h index 67964dc4db95..5cea929b2219 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); __assert_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)); __assert_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)); __assert_shared_cap(l); } while (0)
These changes look wrong to me. The current behavior of lockdep_assert_held(lock) is that it issues a kernel warning at runtime if `lock` is not held when a lockdep_assert_held() statement is executed. __assert_cap(lock) tells the compiler to *ignore* the absence of __must_hold(lock). I think this is wrong. The compiler should complain if a __must_hold(lock) annotation is missing. While sparse does not support interprocedural analysis for lock contexts, the Clang thread-safety checker supports this. If function declarations are annotated with __must_hold(lock), Clang will complain if the caller does not hold `lock`. In other words, the above changes disable a useful compile-time check. I think that useful compile-time checks should not be disabled. Bart.
