On Fri, 2013-06-21 at 15:52 +0200, Sebastian Andrzej Siewior wrote:
> * Mike Galbraith | 2013-06-19 16:26:18 [+0200]:
>
> >
> >The below is what I use to run -rt on UV boxen, diff generated against
> >3.8-rt. Should the lock conversions perhaps wander to mainline?
>
> They seem to come from NMI or irq off region so if you can't change this
> why not.
Maybe SGI can, they know what a bau is. I only made their locks happy.
> >Signed-off-by: Mike Galbraith <bitbucket@xxxxxxxxx>
> >
> >Index: linux-2.6/arch/x86/platform/uv/uv_time.c
> >===================================================================
> >--- linux-2.6.orig/arch/x86/platform/uv/uv_time.c
> >+++ linux-2.6/arch/x86/platform/uv/uv_time.c
> >@@ -300,13 +300,18 @@ static int uv_rtc_unset_timer(int cpu, i
> > static cycle_t uv_read_rtc(struct clocksource *cs)
> > {
> > unsigned long offset;
> >+ cycle_t cycles;
> >
> >+ migrate_disable();
> > if (uv_get_min_hub_revision_id() == 1)
> > offset = 0;
> > else
> > offset = (uv_blade_processor_id() * L1_CACHE_BYTES) % PAGE_SIZE;
> >
> >- return (cycle_t)uv_read_local_mmr(UVH_RTC | offset);
> >+ cycles = (cycle_t)uv_read_local_mmr(UVH_RTC | offset);
> >+ migrate_enable();
> >+
> >+ return cycles;
> > }
> You try to ensure not to switch CPUs between uv_blade_processor_id() and
> uv_read_local_mmr()'s final HW access, right?
Yeah. I originally did preempt_disable/enable() a couple years ago
while convincing a UV to boot/run 2.6.33-rt (x2apic dmar intr_remap
etc), it turned into migrate_disable/enable() as time passed. I'm not
so sure it's really enough, but I was recently given a UV2000 to tinker
with, and both it and old UV100 box boot and (seem to) run fine as is.
-Mike
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