mchehab: Bom dia!
moikka!
sailus: wow, documentation! :-)
sailus: BTW, I've picked up the cec.rstpatch
hverkuil: Thank you!
I thought of documenting things because we're lacking it in a few places. I'll have a few more patches of the same.
mchehab: How do you do?
fine. and you?
Fine, too, thanks!
I had a look on the DVB drivers and it seems at least some of the DVB interfaces suffer from similar issues than MC.
Specifically, releasing the memory of the device node is not serialised with IOCTL calls that access that memory.
I don't remember struct names right now, it's been a while since I read the code.
I was wondering whether to leave it as such for now.
It could possibly be fixed later on.
I don't remember the specifics from the DVB code, but I guess it uses cdev right, so it should be ok
I don't remember any issue at race issue the DVB side with fast plugging/unplugging devices (and I didn't get any of those on my fast bind/unbind loop with au0828 driver)...
except with regards to the frontend kthread, with is a bit sensible
and whose code had to be modified a few times to avoid race issues
there is still a patch pending to merge changing something there for a while...
but to be frank, I'm not too comfortable of merging it, as it could cause more harm than good
so, I keep postponing merging it until either me or someone else with experience would find some time to do a comprehensive test
the logic there properly handle disconnects when the USB driver notifies the core about it (this is a patch that shuah added to fix a race condition she found with her au0828 hardware)
sailus: ^
hi
after trying to install a dvb-s2 device my logitech webcam does not work any more. /dev/video0 not existent and modprobe "ERROR: could not insert 'uvcvideo': Invalid argument
what could be the issue? i tried to remove the changes and reinstalled uvc and v4l components but no change
what device? how did you install it?
lsusb sais " ID 046d:08ce Logitech, Inc. QuickCam Pro 5000"
i did not really install it. it just worked using v4l until i tried to install the dvb-s2 device
mchehab: Ack.
The time window during which bad things can happen isn't large so it's difficult to hit it.
Nevertheless, I'll see how to best proceed with the current set, ensuring the serialisation issues are not made worse on DVB.
sailus: I ran ~10K continuous bind/unbind loops, while 4 other processes were running ioctls on the device, on a 4CPU machine... that's confident enough that a random user on a normal app won't have pains ;)
(in practice)
Ok, there are always space for improvements
but the probability of a race condition there seems low
I do have a compliant about one guy whose device driver is continually binding/unbinding, causing duplicate sysfs filenames
with is indeed a race condition
in his specific case, I suspect that the problem is due to a hardware error, as he's getting error -71
(with is a timeout error at the USB message send/receive)
not sure if the duplicated sysfs names is caused by a problem at the DVB driver or at the USB core
anyway, the error is not due to ioctl's being hit at the wrong moment...
mchehab?
but, instead, because the sysfs cdev is dropped too late
__raven__: I meant: how did you install the dvb driver?
mchehab: ii just installed xawtv, dvb-apps, dvbtune- dvb-tools and dvbv5-*
I guess the DVB driver - or core - is  de-reserved the adapter number too early, e. g. before the sysfs cdev struct device kref is dropped
__raven__: none of those should affect the webcam
mchehab: have you seen this patch: "[PATCH v3 11/16] media: utilize new cdev_device_add helper function"
Even though linux-media was included, this series never made it to our mailinglist for some reason, but it should be in your personal mailbox.
I saw this series
the sysfs file should be removed in the driver unregister() callback. If they are instead removed in the device release callback (or any other release callback) there is a race
I acked it, looked good to me. But you should probably review it as well.
mchehab: what could i try to get the cam back?
hverkuil: the patch itself looks ok. didn't check the implementation, as I was not c/c on patch 01/16
larsc: I'm almost sure that the cdev's /bus/class sysfs file is created internally at the cdev's code
freeing it outside it seems wrong
__raven__: the ERROR: could not insert 'uvcvideo': Invalid argument
indicates an error when loading a Kernel module
installing userspace tools like xawtv, dvb-apps, dvbtune- dvb-tools and dvbv5-* wouldn't cause it
i did not change any kernelspace things. do you know where the module is included in?
you either: installed some Kernel modules, changed something at your /etc/modprobe.d/* or installed some proprietary software that damaged it
i didnt
dmesg may provide you more information about the error
that i am wondering about
if you didn't, then you got hacked ;-)
mchehab: ok. Same comment applies to cdev_del() which will remove the sysfs files
(more likely that you did, by accident)
mchehab: it does but i do not know what to read out of it: http://pastebin.com/UaXVHkws
[    9.434970] uvcvideo: disagrees about version of symbol vb2_queue_release
you installed a new driver
with conflicts with an existing one
try reinstalling your Kernel
that should fix the issue
http://www.linuxforen.de/forums/showthread.php?274740-v4l-(dvb-s)-und-uvcvideo-(webcam) ?
no, I mean something like: apt-get install --reinstall kernel
or dnf reinstall kernel
(no idea what distro you use - but most distros have something similar to it)
and i am talking about a possible reason or how to avoid this to go on ;)
just reinstalled. brb...
but from the pictures, it seems to be in the right direction ;)
hard to tell, though
no still same issue
then you have duplicated drivers
you'll need to find and remove them
some distros (Ubuntu, Debian) uses a non-standard directory for drivers
I guess it is usually called extra/ (or something like that)
you could do something like:
its a debian
(dangerous)
# rm -rf /lib/modules/$(uname -r)
and reinstall the Kernel
but be careful that this will remove all drivers - if you boot the machine without reinstalling the Kernel, you may lose network
and other drivers
perhaps, you could do, instead:
# mv /lib/modules/$(uname -r) /lib/modules/$(uname -r).old
#apt-get install --reinstall kernel
this way, if something gets wrong, you'll still have your drivers at /lib/modules/$(uname -r).old
so you can rename it again
on Fedora, the two non-standard dirs are "extra" and "updates" - not sure about Debian
ok i will try that when i am back home. tnx so far :)
anytime
hey
cam works again - kernel reinstall...but a previous one