Re: AGP bogosities

[Linus Torvalds]

On Sat, 12 Mar 2005, OGAWA Hirofumi wrote:
> 
> diff -puN include/asm-i386/atomic.h~detect-atomic-counter-underflows include/asm-i386/atomic.h
> --- 25/include/asm-i386/atomic.h~detect-atomic-counter-underflows	Wed Nov  3 15:27:37 2004
> +++ 25-akpm/include/asm-i386/atomic.h	Wed Nov  3 15:27:37 2004
> @@ -132,6 +132,10 @@ static __inline__ int atomic_dec_and_tes
>  {
>  	unsigned char c;
>  
> +	if (!atomic_read(v)) {
> +		printk("BUG: atomic counter underflow at:\n");
> +		dump_stack();
> +	}

Btw, this should probably check for negative 32-bit values too, ie the 
test should probably be

	if ((int)atomic_read(v) <= 0)

and it should probably be done for the regular atomic_dec() etc cases too, 
not just the dec-and-test. "atomic" values simply aren't historically 
well-defined for negative values (sparc used to limit them to 24 bits), so 
a negative thing would always be a bug, I think.

		Linus
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