Hallo Dave,
On Fri, 2010-01-22 at 09:32 -0500, Dave Anderson wrote:
> ----- "Michael Holzheu" <holzheu@xxxxxxxxxxxxxxxxxx> wrote:
>
> > Hi Dave,
> >
> > I have a problem with a dump where I have defined five CPUs and two of
> > them are offline. In fact the logical CPUs are defined as follows:
> >
> > 0 on
> > 1 on
> > 2 off
> > 3 off
> > 4 on
> >
> > The CPU online map looks correct:
> >
> > crash> print/x *cpu_online_mask
> > $4 = {
> > bits = {0x13} ---> b10011
> > }
> >
> > When I issue "ps" I see that all running tasks are idle, but the CPU
> > numbers are not correct (0,1,2 and not 0,1,4):
> >
> > PID PPID CPU TASK ST %MEM VSZ RSS COMM
> > > 0 0 0 800ef0 RU 0.0 0 0 [swapper]
> > > 0 0 1 18c24240 RU 0.0 0 0 [swapper]
> > > 0 0 2 18c2c340 RU 0.0 0 0 [swapper]
> >
> > I tried to debug the problem, but got stuck somewhere in "task.c". I
> > think there is a problem with the idle threads initialization, where the
> > online map is not considered.
> >
> > Maybe you can see the bug immediately. Otherwise I will have spend more
> > effort for debugging that problem. I hope not :-)
>
> Does "sys" show 5 or 3 cpus? I'm guessing it shows 3, but should show 5.
Yes it shows 3.
> It looks like the s390/s390x files need to use "get_highest_cpu_online()-1"
> (like x86_64 and ppc64) in order to determine the number of cpus to account
> for. As it is now, they do this, and would therefore only account for the
> first 3 cpus:
>
> int
> s390x_get_smp_cpus(void)
> {
> return get_cpus_online();
> }
>
> int
> s390_get_smp_cpus(void)
> {
> return get_cpus_online();
> }
Hmmm ok...
When I change get_smp_cpus() to return "get_highest_cpu_online() + 1" I
see five swapper idle tasks when using "ps". The problem I now have is
that I have to provide a backtrace for the offline cpus. But the offline
CPUs do not have any stack on s390. Is there a way to tell crash that
there is no backtrace available? Probably I overlooked something...
Michael
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