linux-kernel - Re: [PATCH v1 1/1] lockdep: Mark chain_hlock_class_idx() with __maybe

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Message-ID: <Z180HFO6a61PtzYm@tardis.local>
Date: Sun, 15 Dec 2024 11:55:08 -0800
From: Boqun Feng <boqun.feng@...il.com>
To: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc: linux-kernel@...r.kernel.org, llvm@...ts.linux.dev,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>, Will Deacon <will@...nel.org>,
	Waiman Long <longman@...hat.com>,
	Nathan Chancellor <nathan@...nel.org>,
	Nick Desaulniers <ndesaulniers@...gle.com>,
	Bill Wendling <morbo@...gle.com>,
	Justin Stitt <justinstitt@...gle.com>
Subject: Re: [PATCH v1 1/1] lockdep: Mark chain_hlock_class_idx() with
 __maybe_unused

Hi Andy,

On Mon, Dec 09, 2024 at 07:08:10PM +0200, Andy Shevchenko wrote:
> When chain_hlock_class_idx() is unused, it prevents kernel builds with clang,
> `make W=1` and CONFIG_WERROR=y:
> 
> kernel/locking/lockdep.c:435:28: error: unused function 'chain_hlock_class_idx' [-Werror,-Wunused-function]
> 
> Fix this by marking it with __maybe_unused.
> 
> See also commit 6863f5643dd7 ("kbuild: allow Clang to find unused static
> inline functions for W=1 build").
> 
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>

This looks fine to me, so I'm going to queue it, but could you do me
favor if you could share the exact configs that would make
chain_hlock_class_idx() an unused fuction in kernel/locking/lockdep.c ?

I might add these information in commit log.

Thanks!

Regards,
Boqun

> ---
>  kernel/locking/lockdep.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
> index bb65abfcfa71..29acd238dad7 100644
> --- a/kernel/locking/lockdep.c
> +++ b/kernel/locking/lockdep.c
> @@ -432,7 +432,7 @@ static inline u16 hlock_id(struct held_lock *hlock)
>  	return (hlock->class_idx | (hlock->read << MAX_LOCKDEP_KEYS_BITS));
>  }
>  
> -static inline unsigned int chain_hlock_class_idx(u16 hlock_id)
> +static inline __maybe_unused unsigned int chain_hlock_class_idx(u16 hlock_id)
>  {
>  	return hlock_id & (MAX_LOCKDEP_KEYS - 1);
>  }
> -- 
> 2.43.0.rc1.1336.g36b5255a03ac
>