Messages in this thread | | | Date | Wed, 23 Jul 2014 16:24:54 +0200 | From | Peter Zijlstra <> | Subject | Re: Random panic in load_balance() with 3.16-rc |
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On Wed, Jul 23, 2014 at 01:30:21PM +0200, Peter Zijlstra wrote: > On Wed, Jul 23, 2014 at 01:11:10PM +0200, Peter Zijlstra wrote: > > On Wed, Jul 23, 2014 at 10:45:46AM +0100, Dietmar Eggemann wrote: > > > Doesn't the picture showing the captured panic reveal more information. > > > Haven't seen it myself, I just saw Peter's reply to your email > > > > Its a general protection fault from somewhere in load_balance(), I send > > you the picture. > > > > It would help to get addr2line of the RIP I suppose. > > > > Michel provided a config, so lemme go try and build that, maybe my gcc > > will generate similar code to his and the function offset is enough > > clue. > > So the code section says the faulting instruction is: > > f3 a5 > > followed by: > > 48 89 c7 85 50 ff ff > > or so. > > My compiled code is 'different', the function is shorter, but there's a > f3 a5 somewhere not too far short of +d7 at +a8. I have (objdump -SD): > > 35a8: f3 a5 rep movsl %ds:(%rsi),%es:(%rdi) > > for_each_cpu_and(i, sched_group_cpus(group), env->cpus) { > unsigned long capacity, capacity_factor, wl; > enum fbq_type rt; > > rq = cpu_rq(i); > 35aa: 48 c7 c1 00 00 00 00 mov $0x0,%rcx > > And that's the only part that could possibly match. > > That looks like the start of find_busiest_queue(). I'm not entirely sure > what the rep movsl is operating on, lemme try and figure that out.
Ah, this appears to be load_balance()'s:
cpumask_copy(cpus, cpu_active_mask);
Which totally doesn't make sense, both src and dst are static storage. Dst is the most interesting since its per-cpu storage, but still.
No way either of those should generate a #GP. Puzzled.
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