Re: perf/ftrace lockup on 3.12-rc6 with trigger code

[Vince Weaver]

On Thu, 24 Oct 2013, Vince Weaver wrote:
> after a month of trying I finally got a small test-case out of my 
> perf_fuzzer suite that triggers a system lockup with just one syscall.
> 
> Attached is the code that triggers it.

And it turns out you can only trigger this specific problem if advanced 
ftrace options are enabled.

CONFIG_KPROBES_ON_FTRACE=y
CONFIG_FUNCTION_TRACER=y
CONFIG_FUNCTION_GRAPH_TRACER=y
CONFIG_STACK_TRACER=y
CONFIG_DYNAMIC_FTRACE=y
CONFIG_DYNAMIC_FTRACE_WITH_REGS=y
CONFIG_FUNCTION_PROFILER=y
CONFIG_FTRACE_MCOUNT_RECORD=y

Urgh, I had turned those on to try to debug something and forgot to 
disable.  I feel like I saw this problem before I had those enabled so I 
guess I have to start from scratch fuzzing to see if I can get a more
generally reproducible trace.

Vince
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