[Crash-utility] [PATCH] Use only tasks on online CPUs for bt -a

[Dave Anderson]

----- "Michael Holzheu" <holzheu at linux.vnet.ibm.com> wrote:

> Hello Dave,
> 
> Currently for "bt -a" also swapper tasks on offline CPUs are printed
> (at least on s390). Wouldn't it be better to only print a backtrace,
> when the task is running on an online CPU?
> 
> My suggestion would be to implement that with the following patch
> by only setting the panic threads for online CPUs. I also attached a
> second alternative patch that fills the active set array only with
> tasks on online CPUs.
> 
> What do you think?
> 
> Michael

I'd prefer not to leave them out of the various internal task arrays,
especially the active_set[] array.  Regardless of their on/offline
status, they do still exist as tasks, have runqueues, etc.

If you're just worried about "bt -a", then why not just catch
the offline status in the for loop inside "if (active)" section
of cmd_bt()?  Or just indicate some kind of "OFFLINE" status in
the output?

Dave


> ---
>  task.c |    8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
> 
> --- a/task.c
> +++ b/task.c
> @@ -5658,8 +5658,12 @@ populate_panic_threads(void)
>          struct task_context *tc;
>  
>  	if (get_active_set()) {
> -		for (i = 0; i < NR_CPUS; i++) 
> -			tt->panic_threads[i] = tt->active_set[i];
> +		for (i = 0; i < NR_CPUS; i++) {
> +			if (kt->cpu_flags[i] & ONLINE)
> +				tt->panic_threads[i] = tt->active_set[i];
> +			else
> +				tt->panic_threads[i] = 0;
> +		}
>  		return;
>  	}
> 
> --
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