rawhide report: 20040715 changes

[Warren Togami]

Alan Cox wrote:
> On Fri, Jul 16, 2004 at 09:35:52AM +0200, Arjan van de Ven wrote:
> 
>>it's chockfull of races still
> 
> 
> Most drivers now days are refcounting and well behaved
> 

Run multiple instance of the following shell script concurrently:

#!/bin/bash
modprobe SOMETHING
modprobe -r SOMETHING
exec $0

Simultaneously probe something viewable from userspace from that module, 
like in /proc (note that in most cases this is possible as non-root)

#!/bin/bash
cat /proc/SOMETHING
exec $0

When testing this around 2.6.4 many drivers blew up spectacularly with 
kernel panics when doing the first script alone, while others either 
paniced or eventually got stuck with a huge refcount due to the second 
script.  Some of these were races and fixed since then, but there are 
undoubtedly many remaining now.  Other means of triggering races during 
unloading scares me, because each test case would need to be designed 
for each specific module.

Warren Togami
wtogami at redhat.com