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SubjectRe: [PATCH 05/19] x86/dumpstack: fix function graph tracing stack dump reliability issues
On Tue, Aug 02, 2016 at 10:59:36PM -0400, Steven Rostedt wrote:
> On Tue, 2 Aug 2016 21:50:12 -0500
> Josh Poimboeuf <jpoimboe@redhat.com> wrote:
>
>
> > diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h
> > index 1e814ae..fc508a7 100644
> > --- a/include/linux/ftrace.h
> > +++ b/include/linux/ftrace.h
> > @@ -795,7 +795,9 @@ struct ftrace_ret_stack {
> > unsigned long func;
> > unsigned long long calltime;
> > unsigned long long subtime;
> > +#if defined(CONFIG_HAVE_FUNCTION_GRAPH_FP_TEST) && !defined(CC_USING_FENTRY)
>
> We need to make a new defined in ftrace.h:
>
> #if defined(CONFIG_HAVE_FUNCTION_GRAPH_FP_TEST) && !defined(CC_USING_FENTRY)
> # define HAVE_FUNCTION_GRAPH_FP_TEST
> #endif
>
> And use that instead of this && complexity.
>
> Or better yet, get rid of the CONFIG_HAVE_FUNCTION_GRAPH_FP_TEST define
> and only have HAVE_FUNCTION_GRAPH_FP_TEST defined in the asm/ftrace.h
> in each arch. Then, x86 could just do;
>
> #ifndef CC_USING_FENTRY
> # define HAVE_FUNCTION_GRAPH_FP_TEST
> #endif

Sounds good. I was thinking I could also add a similar define to
indicate whether an arch passes the return address stack pointer to
ftrace_push_return_trace(). HAVE_FUNCTION_GRAPH_RET_ADDR_PTR?

--
Josh

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