Re: Bug while executing : cat /proc/iomem on 2.6.17-rc1/rc2

[Russell King <rmk+lkml@arm.linux.org.uk>]

On Thu, May 11, 2006 at 12:57:48PM +0530, Sharyathi Nagesh wrote:
> I was able to replicate the Bug, even when all the drivers are built into the kernel. 
> It looks like while traversing through p->parent field of resource structure is leading to NULL pointer. 
> Would it be appropriate to make the following code change. 
> 	But I found cat /proc/iomem hangs after line kernel data..
> 
> --- kernel/resource.c.old       2006-05-11 05:29:33.000000000 -0700
> +++ kernel/resource.c   2006-05-11 05:29:58.000000000 -0700
> @@ -81,7 +81,7 @@ static int r_show(struct seq_file *m, vo
>         int depth;
> 
>         for (depth = 0, p = r; depth < MAX_IORES_LEVEL; depth++, p = p->parent){
> -               if (p->parent == root)
> +               if (p->parent == root || p->parent == NULL)
>                         break;
>         }
>         seq_printf(m, "%*s%0*lx-%0*lx : %s\n",

Only the root should have a NULL parent, so this is just covering up some
other problem - you have a resource which somehow has illegally ended up
with a NULL parent pointer while it's been registered.

Maybe try adding:

		if (p->parent == NULL) {
			printk("resource with null parent: %lx-%lx: %s\n",
				p->start, p->end, p->name);
			break;
		}

just before the test in that loop, and then finding out why that resource
is becoming invalid.

-- 
Russell King
 Linux kernel    2.6 ARM Linux   - http://www.arm.linux.org.uk/
 maintainer of:  2.6 Serial core