Re: dynamic ftrace - graph

[Michal Simek]

Steven Rostedt wrote:
> On Fri, 2009-12-11 at 16:28 +0100, Michal Simek wrote:
> > Steven Rostedt wrote:
> > > On Fri, 2009-12-11 at 15:40 +0100, Michal Simek wrote:
> > > > Steven Rostedt wrote:
> > > > > Hey, if they work and they are only in your arch, then I'm fine with
> > > > > them ;-)
> > > > yeah. There is one just small hook to recordmcount.pl. :-)
> > > I may need to give an acked-by. If I did not yet, could you send me that
> > > specific patch.
> > I sent that patches to LKML last month - you were cc'd.
> > http://lkml.org/lkml/2009/11/23/48
>
> They are probably still in the "todo" pile ;-)

:-)

> > You should get it in your mailbox
> >
> > That part is pretty easy. :-)
> >
> > diff --git a/scripts/recordmcount.pl b/scripts/recordmcount.pl
> > index 090d300..b30dabd 100755
> > --- a/scripts/recordmcount.pl
> > +++ b/scripts/recordmcount.pl
> > @@ -245,6 +245,9 @@ if ($arch eq "x86_64") {
> >       $ld .= " -m elf64_sparc";
> >       $cc .= " -m64";
> >       $objcopy .= " -O elf64-sparc";
> > +} elsif ($arch eq "microblaze") {
> > +    # Microblaze calls '_mcount' instead of plain 'mcount'.
> > +    $mcount_regex = "^\\s*([0-9a-fA-F]+):.*\\s_mcount\$";
> >   } else {
> >       die "Arch $arch is not supported with CONFIG_FTRACE_MCOUNT_RECORD";
> >   }
>
> If that's all it is, then here:

yes.
> Acked-by: Steven Rostedt <rostedt@xxxxxxxxxxx>

I don't expect it.:-)

> > > > we will see. Currently I have small problem only with irqsoff but I 
> > > > think this don't have connection with ftrace - only with lockdep I 
> > > > think. :-)
> > > You have lockdep working?  If you get lockdep working you should get the
> > > irqsoff tracer for free.
> > I have some problems when I turn on lockdep debug (CONFIG_DEBUG_LOCKDEP) 
> > - kernel freeze for currently unknown reason.
> > I saw that some arch has some part of code in entry.S but I haven't had 
> > a time to look at them - maybe needs some changes there too.
>
> Yeah, anytime you disable interrupts or enable them (including when the
> hardware does it from entering an exception), you need to call into the
> lockdep infrastructure (trace_hardiqs_on/off){_caller}.

yes that's missing.

> > As you can see below locking testsuite output looks fine but irqsoff 
> > tracer freeze the kernel. Function tracer is ok.
> >
> > There could be a problem with some arch specific functions which 
> > shouldn't be compiled with -pg.
>
> Does it still freeze if you don't enable the function tracer?

look below.

> > Any suggestions? :-)
>
>
> > # cd /
> > # mkdir debug
> > # mount -t debugfs none /debug
> > # cat /debug/tracing/available_tracers
> > irqsoff function sched_switch nop
> > # echo irqsoff > /debug/tracing/current_tracer
> >
> > and kernel freeze. :-(
>
> Try it without configuring function tracer, or you could also do:

uclinux login: root
Password:
Login incorrect
uclinux login: root
Password:
# cd /
# mkdir debug
# mount -t debugfs none /debug/
# cat /debug/tracing/available_tracers
irqsoff sched_switch nop
# echo irqsoff > /debug/tracing/current_tracer


Also freeze - the problem is that low level code. I will look at it next 
week.

Thanks,
Michal

> echo 0 > /proc/sys/ftrace_enabled
>
> That will also disable the function tracer.
>
> -- Steve


--
Michal Simek, Ing. (M.Eng)
w: www.monstr.eu p: +42-0-721842854
Maintainer of Linux kernel 2.6 Microblaze Linux - http://www.monstr.eu/fdt/
Microblaze U-BOOT custodian
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