Re: [PATCH] m32r: Revise __raw_read_trylock()

[Andrew Morton <akpm@osdl.org>]

On Mon, 25 Sep 2006 16:47:22 +0900
Hirokazu Takata <takata.hirokazu@renesas.com> wrote:

> Andrew, please drop and replace the previous my patch with the following
> Matthew's fix.
> 
> Thank you.
> 
> Signed-off-by: Hirokazu Takata <takata@linux-m32r.org>
> Cc: Matthew Wilcox <matthew@wil.cx>
> --
>  include/asm-m32r/spinlock.h |    9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/include/asm-m32r/spinlock.h b/include/asm-m32r/spinlock.h
> index f94c1a6..f9f9072 100644
> --- a/include/asm-m32r/spinlock.h
> +++ b/include/asm-m32r/spinlock.h
> @@ -298,7 +298,14 @@ #endif	/* CONFIG_CHIP_M32700_TS1 */
>  	);
>  }
>  
> -#define __raw_read_trylock(lock) generic__raw_read_trylock(lock)
> +static inline int __raw_read_trylock(raw_rwlock_t *lock)
> +{
> +	atomic_t *count = (atomic_t*)lock;
> +	if (atomic_dec_return(count) >= 0)
> +		return 1;
> +	atomic_inc(count);
> +	return 0;
> +}

We don't have a changelog for this patch.  My usual technique when this
happens is to mutter something unprintable then go on a hunt through the
mailing list archives.

But all I have is "Matthew Wilcox pointed out that
generic__raw_read_trylock() is unfit for use.".

What's wrong with it?