On 3/29/21 9:59 PM, Alistair Popple wrote:
...

quoted

quoted

   		res->desc = IORES_DESC_DEVICE_PRIVATE_MEMORY;
+		if (dev) {
+			dr->parent = &iomem_resource;
+			dr->start = addr;
+			dr->n = size;
+			devres_add(dev, dr);
+		}
+
+		write_unlock(&resource_lock);
+		revoke_iomem(res);

This is new, and not mentioned in the commit log, and therefore quite
surprising. It seems like the right thing to do but it also seems like a
different fix! I'm not saying that it should be a separate patch, but it
does seem worth loudly mentioning in the commit log, yes?

This isn't a different fix though, it is just about maintaining the original
behaviour which called revoke_iomem() after dropping the lock. I inadvertently
switched this around in the initial patch such that revoke_iomem() got called
with the lock, leading to deadlock on x86 with CONFIG_IO_STRICT_DEVMEM=y.

This does change the order of revoke_iomem() and devres_add() slightly, but as
far as I can tell that shouldn't be an issue. Can call that out in the commit
log.

Maybe that's why it looked like a change to me. I do think it's worth mentioning.


thanks,
-- 
John Hubbard
NVIDIA