[Crash-utility] [PATCH] fix missing RT PRIO_ARRAY table with CONFIG_RT_GROUP_SCHED=n

[Dave Anderson]

----- Original Message -----
> On the kernel with CONFIG_RT_GROUP_SCHED=n, the "RT PRIO_ARRAY" table of runq
> command always empty, nevertheless exists "rt_sched_class" task.
> 
> This cause to substract offset "task_struct->rt - task_struct" only if there is
> my_q member (ie. CONFIG_RT_GROUP_SCHED=y). Therefore dump_RT_prio_array()
> passes the address of "rt member of task_struct" to task_to_context().
> 
> This patch ensure to pass the address of "task_struct" to task_to_context().

But moving the task_addr assignment down to where you have placed it will
not work when OFFSET(task_struct_rt) is invalid.  Look above the for loop,
where it has this:

                if (VALID_MEMBER(task_struct_rt) &&
                    VALID_MEMBER(sched_rt_entity_run_list))
                        ld->list_head_offset = OFFSET(sched_rt_entity_run_list);
                else
                        ld->list_head_offset = OFFSET(task_struct_run_list);

So it looks like it should be:

+               if (VALID_MEMBER(task_struct_rt)
+                       task_addr -= OFFSET(task_struct_rt);
+               else
+                       task_addr -= (task_struct_run_list);

And BTW, what does the failure look like?

Thanks,
  Dave


> ---
>  task.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/task.c b/task.c
> index 147ff5c..50c82c8 100644
> --- a/task.c
> +++ b/task.c
> @@ -8688,9 +8688,9 @@ dump_RT_prio_array(ulong k_prio_array, char
> *u_prio_array)
>  						&rt_rq_buf[OFFSET(rt_rq_active)]);
>  					FREEBUF(rt_rq_buf);
>  					continue;
> -				} else
> -					task_addr -= OFFSET(task_struct_rt);
> +				}
>  			}
> +			task_addr -= OFFSET(task_struct_rt);
>  			if (!(tc = task_to_context(task_addr)))
>  				continue;
>  
> --
> 1.9.1
> 
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