lkml.org 
[lkml]   [2018]   [Jan]   [8]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: dvb usb issues since kernel 4.9
On Mon, 8 Jan 2018, Linus Torvalds wrote:

> Can somebody tell which softirq it is that dvb/usb cares about?

I don't know about the DVB part. The USB part is a little difficult to
analyze, mostly because the bug reports I've seen are mostly from
people running non-vanilla kernels. For example, Josef is using a
Raspberry Pi 3B with a non-standard USB host controller driver:
dwc_otg_hcd is built into raspbian in place of the normal dwc2_hsotg
driver.

Both dwc2_hsotg and ehci-hcd use the tasklets embedded in the
giveback_urb_bh member of struct usb_hcd. See usb_hcd_giveback_urb()
in drivers/usb/core/hcd.c; the calls are

else if (high_prio_bh)
tasklet_hi_schedule(&bh->bh);
else
tasklet_schedule(&bh->bh);

As it turns out, high_prio_bh gets set for interrupt and isochronous
URBs but not for bulk and control URBs. The DVB driver in question
uses bulk transfers.

xhci-hcd, on the other hand, does not use these tasklets (it doesn't
set the HCD_BH bit in the hc_driver's .flags member).

Alan Stern

\
 
 \ /
  Last update: 2018-01-14 23:18    [W:0.252 / U:2.272 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site