Re: [PATCH] ia64 cpuset + build_sched_domains() mangles structures

[Dinakar Guniguntala <dino@in.ibm.com>]

On Mon, Aug 22, 2005 at 06:07:19PM +0200, Ingo Molnar wrote:
> great! Andrew, i'd suggest we try the merged patch attached below in 
> -mm.
> 

Ingo, unfortunately I am hitting panic's on stress testing. The panic
screen is attached in the .png below.

On debugging I found that the panic happens consistently in this line
 of code in function find_busiest_group

	*imbalance = min((max_load - avg_load) * busiest->cpu_power,
                                (avg_load - this_load) * this->cpu_power)
                        / SCHED_LOAD_SCALE;

Here I find that the "this" pointer is still NULL. I verified this by
a quick hack as below in the same function and with this hack it seems 
to run for hours

-	if (!busiest || this_load >= max_load)
+	if (!this || !busiest || this_load >= max_load)

This can only happen if the none of the sched groups pointed to by the 
'sd' of the current cpu contain the current cpu. I was wondering if
this had anything to do with the way that we are using RCU to assign/
read the 'sd' pointer.

Any thoughts ??

	-Dinakar