Re: [PATCH] asm-i386/atomic.h: local_irq_save should be used instead of local_irq_disable

["linux-os \(Dick Johnson\)" <linux-os@analogic.com>]

On Tue, 11 Apr 2006, lepton wrote:

> Hi!
> 	When I read the kernel codes, I think this perhaps be a little
> 	bug, What do you think about this?
>
> 	See the following patch (against 2.6.16.3)
>
> Signed-off-by: Lepton Wu <ytht.net@gmail.com>
>
> diff -pru linux-2.6-curr.orig/include/asm-i386/atomic.h linux-2.6-curr.lepton/include/asm-i386/atomic.h
> --- linux-2.6-curr.orig/include/asm-i386/atomic.h	2006-04-06 09:21:53.000000000 +0800
> +++ linux-2.6-curr.lepton/include/asm-i386/atomic.h	2006-04-11 20:47:39.000000000 +0800
> @@ -189,6 +189,7 @@ static __inline__ int atomic_add_return(
> {
> 	int __i;
> #ifdef CONFIG_M386
> +	unsigned long flags;
> 	if(unlikely(boot_cpu_data.x86==3))
> 		goto no_xadd;
> #endif
> @@ -202,10 +203,10 @@ static __inline__ int atomic_add_return(
>
> #ifdef CONFIG_M386
> no_xadd: /* Legacy 386 processor */
> -	local_irq_disable();
> +	local_irq_save(flags);
> 	__i = atomic_read(v);
> 	atomic_set(v, i + __i);
> -	local_irq_enable();
> +	local_irq_restore(flags);
> 	return i + __i;
> #endif
> }

You need to disable interrupts on the local CPU! So, you would need
to save the flags, disable the interrupts, then restore the flags
after the atomic operations.

Cheers,
Dick Johnson
Penguin : Linux version 2.6.15.4 on an i686 machine (5589.42 BogoMips).
Warning : 98.36% of all statistics are fiction, book release in April.
_


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