Re: [PATCH] x86-64: Fix bad assumption that dualcore cpus have synced TSCs

["Vladimir B. Savkin" <master@sectorb.msk.ru>]

On Fri, Oct 07, 2005 at 02:31:46PM +0200, Andi Kleen wrote:
> On Friday 07 October 2005 14:26, Vladimir B. Savkin wrote:
> > On Mon, Sep 19, 2005 at 12:16:43PM -0700, john stultz wrote:
> > > 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
> >
> > I too have a box that shows the symptoms from bugzilla entry above.
> > The system is Asus A8V Deluxe MB with
> > "AMD Athlon(tm) 64 X2 Dual Core Processor 3800+".
> >
> > The patch below did not fix the problem, while "idle=poll" did.
> > Hope this helps, dmesg attached.
> 
> Are you running the latest BIOS?

Just upgraded to the lastest BIOS (revision 1014), nothing changed.
Only with "idle=poll" timers run normally.

> 
> > > 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;
> >
> > ~
~
:wq
                                        With best regards, 
                                           Vladimir Savkin.