linux-kernel - Re: [PATCH v3 05/12] locking/ww_mutex: Remove the __ww_mutex

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Message-ID: <20161223104844.GN3107@twins.programming.kicks-ass.net>
Date:   Fri, 23 Dec 2016 11:48:44 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Nicolai Hähnle <nhaehnle@...il.com>
Cc:     linux-kernel@...r.kernel.org,
        Nicolai Hähnle <Nicolai.Haehnle@....com>,
        Ingo Molnar <mingo@...hat.com>,
        Maarten Lankhorst <dev@...ankhorst.nl>,
        Daniel Vetter <daniel@...ll.ch>,
        Chris Wilson <chris@...is-wilson.co.uk>,
        dri-devel@...ts.freedesktop.org
Subject: Re: [PATCH v3 05/12] locking/ww_mutex: Remove the __ww_mutex_lock
 inline wrappers

On Wed, Dec 21, 2016 at 07:46:33PM +0100, Nicolai Hähnle wrote:
> diff --git a/include/linux/ww_mutex.h b/include/linux/ww_mutex.h
> index a5960e5..b2eaaab 100644
> --- a/include/linux/ww_mutex.h
> +++ b/include/linux/ww_mutex.h
> @@ -186,11 +186,6 @@ static inline void ww_acquire_fini(struct ww_acquire_ctx *ctx)
>  #endif
>  }
>  
> -extern int __must_check __ww_mutex_lock(struct ww_mutex *lock,
> -					struct ww_acquire_ctx *ctx);
> -extern int __must_check __ww_mutex_lock_interruptible(struct ww_mutex *lock,
> -						      struct ww_acquire_ctx *ctx);
> -
>  /**
>   * ww_mutex_lock - acquire the w/w mutex
>   * @lock: the mutex to be acquired
> @@ -220,10 +215,8 @@ extern int __must_check __ww_mutex_lock_interruptible(struct ww_mutex *lock,
>   *
>   * A mutex acquired with this function must be released with ww_mutex_unlock.
>   */
> -static inline int ww_mutex_lock(struct ww_mutex *lock, struct ww_acquire_ctx *ctx)
> -{
> -	return __ww_mutex_lock(lock, ctx);
> -}
> +extern int __must_check ww_mutex_lock(struct ww_mutex *lock,
> +				      struct ww_acquire_ctx *ctx);
>  
>  /**
>   * ww_mutex_lock_interruptible - acquire the w/w mutex, interruptible
> @@ -255,11 +248,8 @@ static inline int ww_mutex_lock(struct ww_mutex *lock, struct ww_acquire_ctx *ct
>   *
>   * A mutex acquired with this function must be released with ww_mutex_unlock.
>   */
> -static inline int __must_check ww_mutex_lock_interruptible(struct ww_mutex *lock,
> -							   struct ww_acquire_ctx *ctx)
> -{
> -	return __ww_mutex_lock_interruptible(lock, ctx);
> -}
> +extern int __must_check ww_mutex_lock_interruptible(struct ww_mutex *lock,
> +						    struct ww_acquire_ctx *ctx);
>  
>  /**
>   * ww_mutex_lock_slow - slowpath acquiring of the w/w mutex
> diff --git a/kernel/locking/mutex.c b/kernel/locking/mutex.c
> index a41bec2..282c6de 100644

For some reason this patch appears to make lib/locking-selftest.c really
unhappy.

I get endless streams of:

../lib/locking-selftest.c: In function ‘ww_test_fail_acquire’:
../lib/locking-selftest.c:1141:6: error: void value not ignored as it ought to be
  ret = WWL(&o, &t);
      ^

Apparently GCC gets confused about __much_check on inline functions or
something, or I got the patch wrong.