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SubjectRe: [PATCH] 2.5: preemptive kernel on UP
On Mon, Mar 04, 2002 at 07:11:23PM -0500, Robert Love wrote:
> During 2.5.5-pre, an optimization was made that removed schedule_tail
> from UP kernels. This causes the initial preempt_count of a new task,
> which starts at 1, to never decrement to zero and thus never become
> preemptible.
>
> Thanks to everyone who pointed out the lousy performance - it took
> awhile to find but it should be fixed now. Please comment if not.
>
> Patch is against 2.5.6-pre2 and is critical for all UP+preempt users.
>
> Robert Love
>
> diff -urN linux-2.5.6-pre2/arch/alpha/kernel/entry.S linux/arch/alpha/kernel/entry.S
> --- linux-2.5.6-pre2/arch/alpha/kernel/entry.S Fri Mar 1 17:21:14 2002
> +++ linux/arch/alpha/kernel/entry.S Mon Mar 4 17:49:27 2002
> @@ -495,7 +495,7 @@
> ret $31,($26),1
> .end alpha_switch_to
>
> -#ifdef CONFIG_SMP
> +#ifdef CONFIG_SMP || CONFIG_PREEMPT

Surely you really don't mean this?

--
Russell King (rmk@arm.linux.org.uk) The developer of ARM Linux
http://www.arm.linux.org.uk/personal/aboutme.html

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