Red Hat Bugzilla – Bug 475376
USB modem locks system when connecting to /dev/ttyUSB0
Last modified: 2014-11-09 17:31:35 EST
Created attachment 326228 [details]
Relevant parts of /var/log/messages during modem usage attempt.
Description of problem:
Using a new USB modem (Novatel USB727), I am getting a full system
lock during the connection process. When F10 came out, this lock
occurred within seconds of clicking on the 'Mobile Broadband'
connection in NetworkManager. Current versions + a (hopefully)
accurate broadband connection configuration in NM produces one of
* Almost connects all the way, then fails with no ill effect
* Hard locks the system during pppd connect call.
I am attaching a recent log of this occurring. The log snippet represents
just the time when the modem was inserted to the lock-up; after the final
line, the machine hard locked.
I'm picking ppp to file this against as that is the component last contacted
in the log. The only relevant message from dmesg seems to be this one:
usb 5-2: reset full speed USB device using uhci_hcd and address 3
Version-Release number of selected component (if applicable):
75%+ ... each attempt does not end in a lock-up, but three out of four
do enough to be reliably broken.
described problem came up with the new modem installation or there were another action starting it?
(In reply to comment #1)
> described problem came up with the new modem installation or there were another
> action starting it?
It seemed to come with the new model installation.
I tried to reproduce under Fedora 9 and didn't get the same effect. I thought it had locked up before, but I updated the entire system before I tested again, so it's hard to know for certain. It did end with a 'CHAP authentication' failure.
That failure is about where the lock up occurs in F10, but it seems strange to freeze on an auth failure.
As of updates on Thursday 12 Dec (all but PackageKit updated), the problem still occurs.
I'm adding Dan Williams so he can consider if this is in fact something going on with NetworkManager.
I can reliably lock-up my F10 system, and have been able to lock-up an F9 system a few times, although usually it just fails CHAP auth and kills the connection attempt.
Since I was able to get this to happen in F9 _after_ ppp negotiates the connection to /dev/ttyUSB0, two further ideas come to mind:
* It is NM locking up while managing the connection
* It is bad hardware
Perhaps I should try another dial-up program? I've never used wvdial but could try.
If the machine hardlocks while being used in any way, that is a kernel or driver issue. Simply shouldn't be happening. I've noticed that recent F9 (2.6.27-41) sometimes hardlocks when disconnecting my Novatel S720 as well, which to me indicates that something in the kernel PPP or USB stacks changed for the worse. It's quite hard to reproduce for me because it's so intermittent.
As it happens, I can make the hardlock happen reliably, within three tries each time. What can I do to figure out where the problem is?
Having it occasionally fall over in F9 is interesting, in that there is a range of kernels I could try. It is also interesting because when it doesn't hardlock in F9, it also does not connect to the ISP with 'CHAP authentication failed' after NM reports '<info> (ttyUSB0): device state change 5 -> 6'. (I'm presuming the Verizon how-to content I've found via google is correct about the password and such, but it's probably worth a call to tech support to confirm I have all the actual configs correct.)
Note that by hardlock, I mean completely unresponsive console. I cannot get in via network because the eth/wlan connections are afaict dropped during the ppp negotiation. However, the fans run, drives spin, USB modem flashes, and the T60 wifi signal light blinks on/off.
I just tried a series of F9 kernels. Two (kernel-188.8.131.52-53.fc9.i686, kernel-184.108.40.206-41.fc9.i686) immediately hardlock after the CHAP auth failure. The third (kernel-220.127.116.11-79.fc9.i686) actually works, with NM throwing up a password dialog, which I apparently have wrong, so I then get CHAP auth failure and pppd actually exits normally. I am able to do this repeatedly without a hardlock.
So ... should I move this to be a kernel bug?
Yeah, probably. The best way to test would be sysrq I guess, since it's certainly not a panic (at least for me, no capslock light blinks when the box locks), so it's a deadlock somewhere in kernel-land.
is there some progress (due to kernel update)? I'll move it to kernel bug if not ...
The original USB modem is no longer with me; lost in the Universe somewhere. (I've been connecting with an LG Voyager tethered via USB cable on F10 with no problems.) I need to get a new USB model soonest, but may not get the same model as before.
If I get that USB modem and am still running F10, then I'll be able to answer yay/nay on this bug. If any of that doesn't work, then probably we should close it as NOTABUG(?)
Meanwhile, I'll (attempt to) leave it in a needinfo on reporter state.
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Approximately 30 (thirty) days from now Fedora will stop maintaining
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Fedora 10 changed to end-of-life (EOL) status on 2009-12-17. Fedora 10 is
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If you can reproduce this bug against a currently maintained version of
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Looks like there was a needinfo on this for me still, I'm adding this comment to clear that (and stop any future alert emails about this bug.)