rt-preempt and x86_64?

rt-preempt and x86_64?

[Alistair John Strachan]

Hi Ingo,

(I searched the list for rt realtime x86_64 x86-64 before posting this, so I 
hope it's not a duplicate).

I've noticed -31 compiles without notable error or warning on x86-64, so I 
thought maybe it was a valid time to file a bug report about it not working.

The machine currently runs 2.6.12 but when booting with PREEMPT_RT mode on the 
same machine I get:

init[1]: segfault at ffffffff8010e9c4 rip ffffffff8010e9c4 rsp 
00007fffffe28018
[...]

Which repeats indefinitely (presumably the kernel tries repeatedly to spawn 
it). I've booted without quiet and a broken root= and the kernel doesn't seem 
to complain about ANYTHING, so this must be a bug.

Any ideas?

-- 
Cheers,
Alistair.

'No sense being pessimistic, it probably wouldn't work anyway.'
Third year Computer Science undergraduate.
1F2 55 South Clerk Street, Edinburgh, UK.

Re: rt-preempt and x86_64?

[Michal Schmidt]

Alistair John Strachan wrote:
> Hi Ingo,
> 
> (I searched the list for rt realtime x86_64 x86-64 before posting this, so I 
> hope it's not a duplicate).
> 
> I've noticed -31 compiles without notable error or warning on x86-64, so I 
> thought maybe it was a valid time to file a bug report about it not working.
> 
> The machine currently runs 2.6.12 but when booting with PREEMPT_RT mode on the 
> same machine I get:
> 
> init[1]: segfault at ffffffff8010e9c4 rip ffffffff8010e9c4 rsp 
> 00007fffffe28018
> [...]

Do you have latency tracing enabled in the kernel config? Try disabling 
it. It's a known problem that it doesn't work on x86_64.

Michal

Re: rt-preempt and x86_64?

[Alistair John Strachan]

On Sunday 17 Jul 2005 17:29, Michal Schmidt wrote:
> Alistair John Strachan wrote:
> > Hi Ingo,
> >
> > (I searched the list for rt realtime x86_64 x86-64 before posting this,
> > so I hope it's not a duplicate).
> >
> > I've noticed -31 compiles without notable error or warning on x86-64, so
> > I thought maybe it was a valid time to file a bug report about it not
> > working.
> >
> > The machine currently runs 2.6.12 but when booting with PREEMPT_RT mode
> > on the same machine I get:
> >
> > init[1]: segfault at ffffffff8010e9c4 rip ffffffff8010e9c4 rsp
> > 00007fffffe28018
> > [...]
>
> Do you have latency tracing enabled in the kernel config? Try disabling
> it. It's a known problem that it doesn't work on x86_64.
>

Thanks Michal, this was the problem. Unless x86_64 is going to receive an 
implementation of LATENCY_TRACE soon, it might be an idea to only let this be 
selectable on x86.

(Unfortunately I couldn't use the resulting kernel anyway, as my lirc modules 
hang the system when modprobe'd; it's probably easy even for me to fix if I 
inspect Ingo's rt-preempt patch.)

-- 
Cheers,
Alistair.

'No sense being pessimistic, it probably wouldn't work anyway.'
Third year Computer Science undergraduate.
1F2 55 South Clerk Street, Edinburgh, UK.