On 15.04.24 11:26, Bjørn Mork wrote:
Oliver Neukum <oneukum@xxxxxxxx> writes:
On 15.04.24 08:47, Bjørn Mork wrote:
urb from service_outstanding_interrupt(). That's why it was added. See
the explanation Robert wrote when introducing it:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/drivers/usb/class/cdc-wdm.c?id=c1da59dad0ebd3f9bd238f3fff82b1f7ffda7829
Well, the explanation is correct in that we must read
data available. However, if the RESPONDING flag is set
and the URB submitted, we are already doing so.
Sounds reasonable. Except that the bug proves we didn't.
Why? I am afraid I do not get that part.
If you are right that service_outstanding_interrupt can race againts
itself (and I don't doubt that), then I guess this could also happen
between failure to submit the URB and clearing the flag?
Yes, it can. In fact in this case the behavior should not change.
I am afraid we have a misunderstanding. It seems to me that in the
unchanged driver the result of service_outstanding_interrupt()
is undefined.
Please explain.
Regards
Oliver
