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 0xfffff, 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 0xfffff, 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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