Re: automated way to find functions that we might want to blacklist

[Sami Liedes <sami.liedes@iki.fi>]

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On Fri, Dec 23, 2011 at 11:10:31PM +0200, Sami Liedes wrote:
> Here's a list of functions that cause Debian's 3.1.0 kernel to crash
> under qemu/kvm for me, found using the script and a fair amount of
> manual testing (because some of them only crash rarely). This list is
> probably not exhaustive; Timo's tool could use some tweaking to enable
> the stress test to be run for longer periods of time and to zero on
> all the functions that only crash sometimes.

After more exhaustive testing and modifying the script to handle
occasional crashes much better, here's an updated list. Should I just
send a patch adding these to the blacklist against the git HEAD of
systemtap?

Note that I've done the tests using systemtap 1.6. Hope that's OK.

Probing any of these functions (eventually) crashes Debian testing's
kernel 3.1.x:

* __find_general_cachep
* arch_local_irq_enable
* arch_local_irq_restore
* clts
* cpu_relax
* hash_64
* hash_ptr
* inat_get_opcode_attribute
* kmem_find_general_cachep
* native_safe_halt
* native_set_debugreg
* native_set_fixmap
* native_write_cr0
* outw
* readl
* rep_nop

I also tested on (mainline) kernel 3.2.0, with the above-mentioned
functions already blacklisted. Placing a probe simultaneously on *all
three* of these functions causes a crash; probing any two but not the
third doesn't seem to crash. Should we just blacklist them all to be
sure?

* test_tsk_thread_flag   AND
* test_tsk_need_resched  AND
* test_ti_thread_flag

	Sami

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