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SubjectRe: [linux-usb-devel] 2.6: USB Storage hangs machine on bootup for ~2 minutes
On Tue, 22 Feb 2005, Parag Warudkar wrote:

> > You said that the system hangs during bootup.  Where in the log does that
> > hang occur?  The log itself looks perfectly normal.  The Maxtor drive is
> > scanned, the partitions detected, and then apparently one or two
> > partitions are mounted.  There's no indication of any problem.
>
> I have tracked down the reason for this hang - it seems that kudzu gets stuck
> in D state on usb_device_read - Below SysRQ+T from 2.6.11-rc4 - always
> reproducible.
>
> kudzu D 00000000ffffffff 0 4424 4472
> (NOTLB)
> ffff81002bebfd98 0000000000000086 ffff81002c538150 ffff81002f21d00e
> 000000078847ce40 ffff81002b5977c0 000000000000fd38 ffffffff803defc0
> ffff81002bebfd88 ffffffff80219b32
> Call Trace:
> <ffffffff80219b32>{_atomic_dec_and_lock+290} <ffffffff80383835>{__down+421}
> <ffffffff80133e30>{default_wake_function+0}
> <ffffffff803868ae>{__down_failed+53}
> <ffffffff802db9f1>{.text.lock.usb+5}
> <ffffffff802edb35>{usb_device_read+229}
> <ffffffff801998d1>{vfs_read+225} <ffffffff80199bd0>{sys_read+80}
> <ffffffff8010ed1e>{system_call+126}
>
> Thereafter, if I try to mount the USB drive, even mount gets stuck.

usb_device_read acquires a couple of locks, one for the USB bus list and
one for the root hub of the bus it's looking at. I don't know which one
occurs at offset 229 on your system -- maybe you can tell. Oddly enough,
neither of those locks is for a USB device like the Maxtor drive. So it's
not at all clear why plugging in the drive should mess up kudzu. Or why
the blockage should clear up after a couple of minutes.

Perhaps we can find out by looking at other entries in the stack trace.
Of particular interest are the khubd, usb-storage, and scsi_eh processes.

Alan Stern

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