linux-kernel - Re: [PATCH v4 06/35] cleanup: Basic compatibility with context analysis

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Message-ID: <aUE77hgJa58waFOy@elver.google.com>
Date: Tue, 16 Dec 2025 12:01:02 +0100
From: Marco Elver <elver@...gle.com>
To: Peter Zijlstra <peterz@...radead.org>
Cc: Boqun Feng <boqun.feng@...il.com>, Ingo Molnar <mingo@...nel.org>,
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Subject: Re: [PATCH v4 06/35] cleanup: Basic compatibility with context
 analysis

On Mon, Dec 15, 2025 at 04:53PM +0100, Marco Elver wrote:
[..]
> > > So I think as is, we can start. But I really do want the cleanup thing
> > > sorted, even if just with that __release_on_cleanup mashup or so.
> >
> > Working on rebasing this to v6.19-rc1 and saw this new scoped seqlock
> > abstraction. For that one I was able to make it work like I thought we
> > could (below). Some awkwardness is required to make it work in
> > for-loops, which only let you define variables with the same type.
> >
> > For <linux/cleanup.h> it needs some more thought due to extra levels of
> > indirection.
> 
> For cleanup.h, the problem is that to instantiate we use
> "guard(class)(args..)". If it had been designed as "guard(class,
> args...)", i.e. just use __VA_ARGS__ explicitly instead of the
> implicit 'args...', it might have been possible to add a second
> cleanup variable to do the same (with some additional magic to extract
> the first arg if one exists). Unfortunately, the use of the current
> guard()() idiom has become so pervasive that this is a bigger
> refactor. I'm going to leave cleanup.h as-is for now, if we think we
> want to give this a go in the current state.

Alright, this can work, but it's not that ergonomic as I'd hoped (see
below): we can redefine class_<name>_constructor to append another
cleanup variable. With enough documentation, this might be workable.

WDYT?

------ >8 ------


diff --git a/include/linux/cleanup.h b/include/linux/cleanup.h
index 2f998bb42c4c..b47a1ba57e8e 100644
--- a/include/linux/cleanup.h
+++ b/include/linux/cleanup.h
@@ -518,7 +518,10 @@ static inline void class_##_name##_destructor(class_##_name##_t *_T) _unlock;
 
 #define DECLARE_LOCK_GUARD_1_ATTRS(_name, _lock, _unlock)		\
 static inline class_##_name##_t class_##_name##_constructor(lock_##_name##_t *_T) _lock;\
-static inline void class_##_name##_destructor(class_##_name##_t *_T) _unlock;
+static __always_inline void __class_##_name##_cleanup_ctx(class_##_name##_t **_T) \
+	__no_context_analysis _unlock {}
+#define WITH_LOCK_GUARD_1_ATTRS(_name, _T) class_##_name##_constructor(_T), \
+	*__UNIQUE_ID(cleanup_ctx) __cleanup(__class_##_name##_cleanup_ctx) = (void *)(_T)
 
 #define DEFINE_LOCK_GUARD_1(_name, _type, _lock, _unlock, ...)		\
 __DEFINE_CLASS_IS_CONDITIONAL(_name, false);				\
diff --git a/include/linux/mutex.h b/include/linux/mutex.h
index 8ed48d40007b..06c3f947ea49 100644
--- a/include/linux/mutex.h
+++ b/include/linux/mutex.h
@@ -255,9 +255,12 @@ DEFINE_LOCK_GUARD_1(mutex, struct mutex, mutex_lock(_T->lock), mutex_unlock(_T->
 DEFINE_LOCK_GUARD_1_COND(mutex, _try, mutex_trylock(_T->lock))
 DEFINE_LOCK_GUARD_1_COND(mutex, _intr, mutex_lock_interruptible(_T->lock), _RET == 0)
 
-DECLARE_LOCK_GUARD_1_ATTRS(mutex, __assumes_ctx_lock(_T), /* */)
-DECLARE_LOCK_GUARD_1_ATTRS(mutex_try, __assumes_ctx_lock(_T), /* */)
-DECLARE_LOCK_GUARD_1_ATTRS(mutex_intr, __assumes_ctx_lock(_T), /* */)
+DECLARE_LOCK_GUARD_1_ATTRS(mutex,	__acquires(_T), __releases(*(struct mutex **)_T))
+DECLARE_LOCK_GUARD_1_ATTRS(mutex_try,	__acquires(_T), __releases(*(struct mutex **)_T))
+DECLARE_LOCK_GUARD_1_ATTRS(mutex_intr,	__acquires(_T), __releases(*(struct mutex **)_T))
+#define class_mutex_constructor(_T)	WITH_LOCK_GUARD_1_ATTRS(mutex, _T)
+#define class_mutex_try_constructor(_T) WITH_LOCK_GUARD_1_ATTRS(mutex_try, _T)
+#define class_mutex_intr_constructor(_T) WITH_LOCK_GUARD_1_ATTRS(mutex_intr, _T)
 
 extern unsigned long mutex_get_owner(struct mutex *lock);