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Subject: Re: [PATCH 3/20] powerpc/mm: Add HW threads support to no_hash TLB
	management
From: Dave Kleikamp <shaggy@linux.vnet.ibm.com>
To: Kumar Gala <galak@kernel.crashing.org>
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Date: Mon, 03 Aug 2009 12:57:45 -0500
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On Mon, 2009-08-03 at 12:06 -0500, Dave Kleikamp wrote:
> On Mon, 2009-08-03 at 11:21 -0500, Kumar Gala wrote:
> > On Aug 2, 2009, at 9:03 PM, Michael Ellerman wrote:
> > 

> > > for (cpu = cpu_first_thread_in_core(cpu);
> > >     cpu <= cpu_last_thread_in_core(cpu); cpu++)
> > >        __clear_bit(id, stale_map[cpu]);
> > >
> > > ==
> > >
> > > cpu = cpu_first_thread_in_core(cpu);
> > > while (cpu <= cpu_last_thread_in_core(cpu)) {
> > > 	__clear_bit(id, stale_map[cpu]);
> > > 	cpu++;
> > > }
> 
> cpu_last_thread_in_core(cpu) is a moving target.  You want something
> like:
> 
> cpu = cpu_first_thread_in_core(cpu);
> last = cpu_last_thread_in_core(cpu);
> while (cpu <= last) {
> 	__clear_bit(id, stale_map[cpu]);
> 	cpu++;
> }

Or, keeping the for loop:

for (cpu = cpu_first_thread_in_core(cpu), last =
cpu_last_thread_in_core(cpu);
     cpu <= last; cpu++)
	cpu++;

> 
> > >
> > > cpu = 0
> > > cpu <= 1
> > > cpu++ (1)
> > > cpu <= 1
> > > cpu++ (2)
> > > cpu <= 3
> > > ...
> > 
> > Which is pretty much what I see, in a dual core setup, I get an oops  
> > because we are trying to clear cpu #2 (which clearly doesn't exist)
> > 
> > cpu = 1
> > (in loop)
> > 	clearing 1
> > 	clearing 2
> > OOPS
> > 
> > - k
> 
-- 
David Kleikamp
IBM Linux Technology Center