linux-kernel - Re: [PATCH v4 02/35] compiler-context-analysis: Add infrastructure for Context Analysis with Clang

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Message-ID: <20251211120441.GG3911114@noisy.programming.kicks-ass.net>
Date: Thu, 11 Dec 2025 13:04:41 +0100
From: Peter Zijlstra <peterz@...radead.org>
To: Marco Elver <elver@...gle.com>
Cc: Boqun Feng <boqun.feng@...il.com>, Ingo Molnar <mingo@...nel.org>,
	Will Deacon <will@...nel.org>,
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Subject: Re: [PATCH v4 02/35] compiler-context-analysis: Add infrastructure
 for Context Analysis with Clang

On Thu, Nov 20, 2025 at 03:49:04PM +0100, Marco Elver wrote:

> +/**
> + * context_guard_struct() - declare or define a context guard struct
> + * @name: struct name
> + *
> + * Helper to declare or define a struct type that is also a context guard.
> + *
> + * .. code-block:: c
> + *
> + *	context_guard_struct(my_handle) {
> + *		int foo;
> + *		long bar;
> + *	};
> + *
> + *	struct some_state {
> + *		...
> + *	};
> + *	// ... declared elsewhere ...
> + *	context_guard_struct(some_state);
> + *
> + * Note: The implementation defines several helper functions that can acquire
> + * and release the context guard.
> + */
> +# define context_guard_struct(name, ...)								\
> +	struct __ctx_guard_type(name) __VA_ARGS__ name;							\
> +	static __always_inline void __acquire_ctx_guard(const struct name *var)				\
> +		__attribute__((overloadable)) __no_context_analysis __acquires_ctx_guard(var) { }	\
> +	static __always_inline void __acquire_shared_ctx_guard(const struct name *var)			\
> +		__attribute__((overloadable)) __no_context_analysis __acquires_shared_ctx_guard(var) { } \
> +	static __always_inline bool __try_acquire_ctx_guard(const struct name *var, bool ret)		\
> +		__attribute__((overloadable)) __no_context_analysis __try_acquires_ctx_guard(1, var)	\
> +	{ return ret; }											\
> +	static __always_inline bool __try_acquire_shared_ctx_guard(const struct name *var, bool ret)	\
> +		__attribute__((overloadable)) __no_context_analysis __try_acquires_shared_ctx_guard(1, var) \
> +	{ return ret; }											\
> +	static __always_inline void __release_ctx_guard(const struct name *var)				\
> +		__attribute__((overloadable)) __no_context_analysis __releases_ctx_guard(var) { }	\
> +	static __always_inline void __release_shared_ctx_guard(const struct name *var)			\
> +		__attribute__((overloadable)) __no_context_analysis __releases_shared_ctx_guard(var) { } \
> +	static __always_inline void __assume_ctx_guard(const struct name *var)				\
> +		__attribute__((overloadable)) __assumes_ctx_guard(var) { }				\
> +	static __always_inline void __assume_shared_ctx_guard(const struct name *var)			\
> +		__attribute__((overloadable)) __assumes_shared_ctx_guard(var) { }			\
> +	struct name

-typedef struct {
+context_guard_struct(rwlock) {
        struct rwbase_rt        rwbase;
        atomic_t                readers;
 #ifdef CONFIG_DEBUG_LOCK_ALLOC
        struct lockdep_map      dep_map;
 #endif
-} rwlock_t;
+};
+typedef struct rwlock rwlock_t;


I must say I find the 'guard' naming here somewhat confusing. This is
not a guard, but an actual lock type.