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    SubjectRe: [PATCH 4/5] ftrace: function graph return for function entry

    * Steven Rostedt <rostedt@goodmis.org> wrote:

    > From: Steven Rostedt <srostedt@redhat.com>
    >
    > Impact: feature, let entry function decide to trace or not
    >
    > This patch lets the graph tracer entry function decide if the tracing
    > should be done at the end as well. This requires all function graph
    > entry functions return 1 if it should trace, or 0 if the return should
    > not be traced.

    > diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
    > index 47aa5f0..cef05a2 100644
    > --- a/arch/x86/kernel/entry_64.S
    > +++ b/arch/x86/kernel/entry_64.S
    > @@ -119,6 +119,9 @@ ENTRY(mcount)
    > #ifdef CONFIG_FUNCTION_GRAPH_TRACER
    > cmpq $ftrace_stub, ftrace_graph_return
    > jnz ftrace_graph_caller
    > +
    > + cmpq $ftrace_graph_entry_stub, ftrace_graph_entry
    > + jnz ftrace_graph_caller

    hm, that's in the hotpath. What's the point of this? Do we want some sort
    of configuration vector that allows per function graphing versus
    entry-only traces?

    Ingo


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