Date: Tue, 30 May 2006 08:15:04 +0200
From: Ingo Molnar <mingo@elte.hu>
To: Simon Derr <Simon.Derr@bull.net>
Cc: linux-kernel@vger.kernel.org, Thomas Gleixner <tglx@linutronix.de>,
       John Stultz <johnstul@us.ibm.com>
Subject: Re: -rt IA64 update
Message-ID: <20060530061503.GA19870@elte.hu>
References: <Pine.LNX.4.61.0605291356170.14092@openx3.frec.bull.fr>
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* Simon Derr <Simon.Derr@bull.net> wrote:

> Hi Ingo,
> 
> This is an update of my IA64 port, against -rt25.

thanks - i have applied it.

> I have modified check_pgt_cache() as we discussed before, and the raw 
> spinlock in the struct zone is no longer needed.

ok, great!

> There's also a preliminary and certainly very bogus attempt to have 
> the HR timers on IA64. I'd love to have comments on that part.
> 
> Some bits of the Kconfig have been stolen from a previous patch by 
> Eric Piel.

i'll let Thomas and John comment on that - but at a quick glance it 
seems quite OK.

> This kernel boots OK on UP and SMP, and runs the sched_football test 
> successfully.
> 
> 
> A few notes:
> 
> * You can see at the end of the patch this ugly thing in 
> clockevents_set_next_event()
> 
> +#ifndef CONFIG_IA64
>         clc = mpy_sc32((unsigned long) delta, sources->nextevt->mult);
> +#else
> +       clc = (unsigned long) delta * (unsigned long) sources->nextevt->mult;
> +       clc = clc >> sources->nextevt->shift;
> +#endif
> +
> 
> I made this ia64-only, but it seems to me that this code should be 
> fixed as it works only for clocksources that have shift=32.

yeah, agreed.

> * This kernel, when booting, prints:
> 
> 	BUG in check_monotonic_clock at kernel/time/timeofday.c:164
> 
> But I think this happens because two get_monotonic_clock() are racing 
> on two cpus. There is a lock to prevent the race, but it is a seqlock. 
> That means that it is okay if the race happens since another try will 
> be attempted, but the message that has been printed on the console 
> can't be removed, and the user is unnecessarily scared.

that too comes from the GTOD patchset. John, should we pick up the 
latest from -mm?

	Ingo
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