Repeatable lockup on SMP w/usbprocfs

Tony Hoyle (tmh@magenta-netlogic.com)
Wed, 28 Mar 2001 21:52:00 +0100

If an application calls the USBDEVFS_SUBMITURB ioctl to submit a read,
when the async completion routine is called, the kernel goes into a hard
deadlock (no response to ping, etc.). I've narrowed it down to the
async_completed routine in usb.c. That's the only place where spinlocks
are used. I'm not familiar enough with them to see what the error is,
though.

The system runs fine until the packet is returned, then it just locks
solid (On the alcatel USB modem I used for testing it will not respond
until it gets sync, which may be several seconds).

Others have found that just compiling SMP into the kernel is enough to
break it, you don't actually need two processors.

Tony

-- 
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tmh@magenta-netlogic.com        http://www.nothing-on.tv


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