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SubjectRe: DDD locked up kernel :o(
My two cents worth:

The ptrace code is fragile. I had a test program that would make the
kernel spin in put_long while holding the kernel lock. I didn't make
the test program by looking for boundary test cases; I made it by running
mec-replay in the normal course of development, watching my kernel hang,
and boiling down a test case.

I think a good place to start is to put a loop counter in get_long
and put_long in arch/*/kernel/ptrace.c and log messages or panic
if the loop counter exceeds 1000. Also drop in some printk's at
the beginning and end of sys_ptrace catch the call sequence. Then add
another two dozen printk's, et cetera.

Michael Elizabeth Chastain
<mailto:mec@shout.net>
"love without fear"

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