Re: 2.6.14-rc2-mm1

[Paul Blazejowski <paulb@blazebox.homeip.net>]

On Mon, Sep 26, 2005 at 09:14:02AM +0200, Tim Schmielau wrote:
> On Sun, 25 Sep 2005, Paul Blazejowski wrote:
> 
> > Upon quick testing the latest mm kernel it appears there's some kind of
> > race condition when using dual core cpu esp when using XORG and USB
> > (although PS2 has same issue) kebyboard rate being too fast.
> 
> Does the following patch by John Stultz fix the problem?
> 
> Tim

Tim,

No it does not, from my understanding it only pertains to x86_64 but
currently i run i386 SMP enabled kernel on the dualcore X2 processor.

Also worth noting is that i do not see any failures or errors in dmesg
related to lost timers. Perhaps this is something new? I even run  a
script from the bugzilla and the output matched both cpu's.

Thanks,

	Paul

> 
> 
> From johnstul@us.ibm.com Mon Sep 26 09:04:08 2005
> Date: Mon, 19 Sep 2005 12:16:43 -0700
> From: john stultz <johnstul@us.ibm.com>
> To: Andrew Morton <akpm@osdl.org>
> Cc: lkml <linux-kernel@vger.kernel.org>, Andi Kleen <ak@suse.de>
> Subject: [PATCH] x86-64: Fix bad assumption that dualcore cpus have synced
>     TSCs
> 
> Andrew,
> 	This patch should resolve the issue seen in bugme bug #5105, where it
> is assumed that dualcore x86_64 systems have synced TSCs. This is not
> the case, and alternate timesources should be used instead.
> 
> For more details, see:
> http://bugzilla.kernel.org/show_bug.cgi?id=5105
> 
> 
> Please consider for inclusion in your tree.
> 
> thanks
> -john
> 
> diff --git a/arch/x86_64/kernel/time.c b/arch/x86_64/kernel/time.c
> --- a/arch/x86_64/kernel/time.c
> +++ b/arch/x86_64/kernel/time.c
> @@ -959,9 +959,6 @@ static __init int unsynchronized_tsc(voi
>   	   are handled in the OEM check above. */
>   	if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL)
>   		return 0;
> - 	/* All in a single socket - should be synchronized */
> - 	if (cpus_weight(cpu_core_map[0]) == num_online_cpus())
> - 		return 0;
>  #endif
>   	/* Assume multi socket systems are not synchronized */
>   	return num_online_cpus() > 1;
> 
> 
>

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