Re: Problem with VMAP_STACK=y

[Jiri Kosina]

On Tue, 4 Oct 2016, JÃrg Otte wrote:

> With kernel 4.8.0-01558-g21f54dd I get thousands of
> "dvb-usb: bulk message failed: -11 (1/0)"
> messages in the logs and the DVB adapter is not working.
> 
> It tourned out the new config option VMAP_STACK=y (which is the default)
> is the culprit.
> No problems for me with VMAP_STACK=n.

I'd guess that this is EAGAIN coming from usb_hcd_map_urb_for_dma() as the 
DVB driver is trying to perform on-stack DMA.

Not really knowing which driver exactly you're using, I quickly skimmed 
through DVB sources, and it turns out this indeed seems to be rather 
common antipattern, and it should be fixed nevertheless. See

	cxusb_ctrl_msg()
	dibusb_power_ctrl()
	dibusb2_0_streaming_ctrl()
	dibusb2_0_power_ctrl()
	digitv_ctrl_msg()
	dtt200u_fe_init()
	dtt200u_fe_set_frontend()
	dtt200u_power_ctrl()
	dtt200u_streaming_ctrl()
	dtt200u_pid_filter()
	
Adding relevant CCs.

-- 
Jiri Kosina
SUSE Labs