Re: USB hub detach causing panic in 4.7p3?! (more information)

[Darren Pilgrim]

Darren Pilgrim wrote:

I'm going to try a few more things, like plugging and unplugging the hub 
with the monitor on, as well as plugging and unplugging devices from 
both the root hub and the hub in the monitor to see if it's more 
general, or if it's just something wrong with the uhub detach routine.

I tried various patterns of plugging and unplugging devices and the hub, 
as well as booting with and without the hub connected and with and 
without additional devices connected to the hub.  The additional device 
was a Microsoft Wireless Intellimouse Explorer.  I should note that I 
have /etc/usbd.conf modified to not run moused when a ums device is 
attached.

In all cases, panics only occured when the hub was detached without 
anything attached to it.  In all other cases the hub and the ums device 
attached to the hub it detached and reattached repeatedly without problems.

While doing this testing, the fault information was different in two 
places: the stack and frame pointer values in the second (after the 
"syncing disks" message) fault information block were different, but 
consistent for all panics:

stack pointer   = 0x10:0xc0250dd0
frame pointer   = 0x10:0xc0250dd8

The first fault's information block and the remaining information from 
the second block was the same as previously reported.

I also looked through my logs and found that, until this afternoon, the 
ums device was always attached when I had turned the monitor off.  My 
logs cover 4.7-R, 4.7p2, and 4.7p3, with over 20 reboots between 1am 
Friday morning and 5pm today, the time of the first panic.

I suppose the question now is: why does uhub cause a page fault when an 
unused hub is detached?  Unused meaning there are no devices hanging off it.

I'd also like to take this moment to thank all the hackers who made 
FreeBSD so damned robust that I could deliberately panic the machine 
over and over and have all the filesystems come up fine every time.


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USB hub detach causing panic in 4.7p3?!

[Darren Pilgrim]

I have a USB hub that's built into my Viewsonic PT775 monitor.  The hub 
works fine, and has worked fine for years in Windows, Linux, and 
FreeBSD.  The USB hub is only attached to the rest of the USB bus when 
the monitor is on, so turning the monitor on or off produces the 
expected uhub attach/detach noticed.  On Friday (Jan 10), I cvsupped and 
recompiled to upgrade from 4.7p2 to 4.7p3.  Prior to this upgrade, I 
know that the attach/dettach process worked without problems.  As of 
about 5pm today, turning the monitor off causes this result (please 
forgive typos, this is a transcription, though I'm over 99.9% sure the 
numbers are correct):

uhub1: at uhub0 port 2 (addr 2) disconnected
uhub1: detached

Fatal trap 12: page fault while in kernel mode
fault virtual addres= 0x3
fault code  = supervisor read, page not present
instruction pointer = 0x8:0xc031fe04
stack pointer   = 0x10:0xc0250fb0
frame pointer   = 0x10:0xc0250fc4
code segment= base 0x0, limit 0xf, type 0x1b
= DPL 0, pres 1, def32 1, gran 1
processor eflags= interrupt enabled, resume, IOPL = 0
current process = Idle
interrupt mask  = bio
trap number = 12
panic: page fault


syncing disks...

Fatal trap 12: page fault while in kernel mode
fault virtual address   = 0x30
fault code  = supervisor read, page not present
instruction pointer = 0x8:0xc01c2498
stack pointer   = 0x10:0xc0250d98
frame pointer   = 0x10:0xc0250da0
code segment= base 0x0, limit 0xf, type 0x1b
= DPL 0, pres 1, def32 1, gran 1
processor eflags= interrupt enabled, resume, IOPL = 0
current process = Idle
interrupt mask  = bio
trap number = 12
panic: page fault
Uptime: 3m57s
--> Press a key on the console to reboot,
--> or switch off the system now.

Nothing is plugged into the hub at the time.  This seems to be a 
reliable panic in that I got the exact same panic when I switch the 
monitor off again later after having warm rebooted.

I can't say beyond now vs. before Friday if the upgrade to 4.7p3 caused 
the problem or not.  Nor can I say for sure that the problem existed 
between Friday and today, as I can't recall if I had turned off the 
monitor while running FreeBSD between now and then (I reboot between 
FreeBSD and Windows multiple times per day).

I made sure to delete the contens of /usr/obj/usr and run make cleandir 
twice before compiling 4.7p3, and I've made no other changes to the 
system configuration beyond adding a couple of X programs 
(x11-fm/asfiles and x11-fm/endeavour).

I'm going to try a few more things, like plugging and unplugging the hub 
with the monitor on, as well as plugging and unplugging devices from 
both the root hub and the hub in the monitor to see if it's more 
general, or if it's just something wrong with the uhub detach routine.

Is this a known problem or does anyone have any suggestions for tracking 
down this problem?


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