linux-kernel - Re: Problem with VMAP

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Date:   Tue, 4 Oct 2016 18:11:50 +0200
From:   Jörg Otte <jrg.otte@...il.com>
To:     Jiri Kosina <jikos@...nel.org>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Andy Lutomirski <luto@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Ingo Molnar <mingo@...nel.org>,
        Michael Krufky <mkrufky@...uxtv.org>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Patrick Boettcher <patrick.boettcher@...teo.de>,
        Linux Media Mailing List <linux-media@...r.kernel.org>
Subject: Re: Problem with VMAP_STACK=y

2016-10-04 15:26 GMT+02:00 Jiri Kosina <jikos@...nel.org>:
> On Tue, 4 Oct 2016, Jörg 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

Thanks for the quick response.
Drivers are:
dvb_core, dvb_usb, dbv_usb_cynergyT2


Jörg