Re: Oops after removing PCMCIA modem with low latency patch

[Andrew Morton <akpm@zip.com.au>]

Diego Biurrun wrote:
> 
> Hello!
> 
> I just tried your 2.4.19-low-latency patch on a stock 2.4.19 kernel and
> my box oopses when I manually remove my PCMCIA modem.

Yup.  The pcmcia drivers like to call sleeping devfs functions
from within a timer handler.  The kernel tries to perform a
context switch in interrupt context and bugs out.  This can happen
without the low-latency patch, but doesn't.

The fix for that is to change the (strange) deferred deregister thing
in several of the CardServices drivers to punt the activity up to
process context via schedule_task(), but nobody has done that yet.

Probably, you can add

	if (in_interrupt())
		return;

to schedule() to make the BUGs go away.   Not using devfs makes
them go away too - but it is not a devfs bug.