Re: [PATCH -v4 4/9] tracing: add static function tracer supportfor MIPS
From: Steven Rostedt
Date: Thu Oct 22 2009 - 17:55:38 EST
On Thu, 2009-10-22 at 14:29 -0700, Adam Nemet wrote:
> Steven Rostedt writes:
> > On Thu, 2009-10-22 at 13:30 -0700, Adam Nemet wrote:
> > > Also note that for functions invoked via tail call you won't get an exit
> > > event. E.g. if bar is tail-called from foo:
> > >
> > > foo entered
> > > bar entered
> > > foo/bar exited
> > >
> > > However, this is not MIPS-specific and you can always disable tail calls
> > > with -fno-optimize-sibling-calls.
> > The question is, would bar have a _mcount call? So far, we have not had
> > any issues with this on either x86 nor PPC.
> Yes, bar will have an _mcount call. The difference is that bar will return to
> foo's caller directly rather than to foo first.
I guess the best bet is to have CONFIG_FUNCTION_GRAPH enable
-fno-optimize-sibling-calls and be done with it.
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