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Backport to 2.4 - the 2.6.4 fix for "BUG at kernel/exit.c:793!" - part 1
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From: Jeff Dike <jdike@addtoit.com>
Cc: user-mode-linux-devel@lists.sourceforge.net

The following stress-test crashed the 2.6 kernel - this was fixed in 2.6.4-1um
release - this is the first part (historically speaking) of the fix:

$ while /bin/true ; do /bin/true ; done 

In fact, a similar stress-test panics 2.4 - you only need to run:

cat /dev/urandom

while running the above test. So I'm backporting this fix, which was thought
as not needed since on 2.4 the simpler stress-test does not panic the kernel.

Quoting from Jeff Dike:
"This turned out to be slightly subtle.  It was exposed by the 
longjmp -> siglongjmp change.  New processes were created with signals 
enabled, so siglongjmp to a new process context re-enabled signals in the
middle of the context switch.

Try the patch below - it seems to fix things for me.

				Jeff"

Note: this is not enough - but it is probably needed, so I'm backporting it
anyway.