Re: Xorg causes panics with "multiple" drivers (Was: panic: resource_list_alloc: resource entry is busy)

On Saturday, September 13, 2014 10:57:53 AM dt71_at_gmx.com wrote:
> John Baldwin wrote on 09/12/2014 23:06:
> > X loaded i915kms automatically and
> > i915 and i915kms do not get along.  i915 had already allocated the IRQ
> > when i915kms tried to alloc the same IRQ causing the issue.
> 
> Who is to blame? The user who tried to manually load an unsupported
> combination of modules, or the system, which should have handled things
> gracefully (whether by automatically unloading the first driver, or
> producing a soft-error upon loading the 2nd driver)?
> 
> On a side-note, I also had a "resource_list_alloc: resource entry is busy"
> panic right after switching from the 10.0-supported Xorg to the "new" Xorg;
> I exited Xorg, enabled "FreeBSD_new_Xorg", ran "pkg upgrade", then ran
> "startx", and got the panic. Surely this wasn't my fault!

I can turn the panic into a resource allocation failure, but specifically with 
KMS I am unsure if it will actually be better.  It depends on when the driver 
does this IRQ allocation.   You may very well end up with a black screen and a 
seemingly "hung" system (though it would not actually be hung).

I do think we should fix i915kms to fail fast if i915 is loaded, or more 
likely I think we should probably look at removing the old i915 driver from 
HEAD entirely so that 11 doesn't ship with it.  It won't work with the Xorg we 
are shipping with 11, so it's really dead code at this point.

The proposed diff would be:

Index: subr_bus.c
===================================================================
--- subr_bus.c	(revision 271627)
+++ subr_bus.c	(working copy)
_at__at_ -3301,7 +3301,10 _at__at_ resource_list_alloc(struct resource_list *rl, devi
 			rle->flags |= RLE_ALLOCATED;
 			return (rle->res);
 		}
-		panic("resource_list_alloc: resource entry is busy");
+		device_printf(bus,
+		    "resource entry %#x type %d for child %s is busy\n", *rid,
+		    type, device_get_nameunit(child));
+		return (NULL);
 	}
 
 	if (isdefault) {

-- 
John Baldwin