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Date: Mon, 27 Mar 2017 09:08:43 -0500 From: Josh Poimboeuf <jpoimboe@...hat.com> To: "Rafael J. Wysocki" <rjw@...ysocki.net> Cc: Steven Rostedt <rostedt@...dmis.org>, Paul Menzel <pmenzel@...gen.mpg.de>, Len Brown <lenb@...nel.org>, linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...nel.org> Subject: Re: [PATCH] acpi: fix incompatibility with mcount-based function graph tracing On Sat, Mar 25, 2017 at 02:20:11PM +0100, Rafael J. Wysocki wrote: > On Friday, March 24, 2017 02:41:14 PM Steven Rostedt wrote: > > On Fri, 24 Mar 2017 13:12:54 -0500 > > Josh Poimboeuf <jpoimboe@...hat.com> wrote: > > > > > > > Instead I was able to "fix" it by ignoring ftrace calls in real mode: > > > > > > ----- > > > index 8f3d9cf..5c0d0c6 100644 > > > --- a/arch/x86/kernel/ftrace.c > > > +++ b/arch/x86/kernel/ftrace.c > > > @@ -983,6 +983,9 @@ void prepare_ftrace_return(unsigned long self_addr, unsigned long *parent, > > > unsigned long return_hooker = (unsigned long) > > > &return_to_handler; > > > > > > + if (__builtin_return_address(0) < TASK_SIZE_MAX) > > > + return; > > > + > > > if (unlikely(ftrace_graph_is_dead())) > > > return; > > > --------------- > > > > > > I'm not sure what the best fix should really be. A few ideas off the > > > top of my head: > > > > > > - A real mode check similar to the above (except it should probably be > > > more precise) > > > > The real mode check hack may be good enough for now. Make sure that > > it's commented well. > > Agreed. Just to clarify, there are two bugs related to function graph tracing and suspend/resume. The original patch in this thread (which removes '-Os' from the acpi Makefile) is still needed. -- Josh
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