linux-kernel - Re: [PATCH, RFC] hacks to allow -rt to run kernbench on POWER

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Date:	Wed, 12 Dec 2007 22:56:12 -0500 (EST)
From:	Steven Rostedt <rostedt@...dmis.org>
To:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
cc:	linux-kernel@...r.kernel.org, tony@...eyournoodle.com,
	paulus@...ba.org, benh@...nel.crashing.org, dino@...ibm.com,
	tytso@...ibm.com, dvhltc@...ibm.com, antonb@...ibm.com
Subject: Re: [PATCH, RFC] hacks to allow -rt to run kernbench on POWER


On Mon, 29 Oct 2007, Paul E. McKenney wrote:
> diff -urpNa -X dontdiff linux-2.6.23.1-rt4/mm/memory.c linux-2.6.23.1-rt4-fix/mm/memory.c
> --- linux-2.6.23.1-rt4/mm/memory.c	2007-10-27 22:20:57.000000000 -0700
> +++ linux-2.6.23.1-rt4-fix/mm/memory.c	2007-10-28 15:40:36.000000000 -0700
> @@ -664,6 +664,7 @@ static unsigned long zap_pte_range(struc
>  	int anon_rss = 0;
>
>  	pte = pte_offset_map_lock(mm, pmd, addr, &ptl);
> +	preempt_disable();
>  	arch_enter_lazy_mmu_mode();
>  	do {
>  		pte_t ptent = *pte;
> @@ -732,6 +733,7 @@ static unsigned long zap_pte_range(struc
>
>  	add_mm_rss(mm, file_rss, anon_rss);
>  	arch_leave_lazy_mmu_mode();
> +	preempt_enable();
>  	pte_unmap_unlock(pte - 1, ptl);
>
>  	return addr;

I'm pulling your patch for the above added code. Took me a few hours to
find the culprit, but I was getting scheduling in atomic bugs. Turns out
that this code you put "preempt_disable" in calls sleeping spinlocks.

Might want to run with DEBUG_PREEMPT.

Thanks,

-- Steve

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