[Crash-utility] Running idle threads show wrong CPU numbers

[Dave Anderson]

----- "Michael Holzheu" <holzheu at linux.vnet.ibm.com> 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.
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();
}

Dave