[PATCH -rt] powerpc/tracing: Add support for "PREEMPT_TRACE" tracer

Anton Vorontsov
2009-01-31T19:14:56Z

The support is pretty straightforward: issue print_preempt_trace()
just after the call trace.

Without CONFIG_PREEMPT_TRACE=y the print_preempt_trace() call turns
into no-op.

Signed-off-by: Anton Vorontsov <avorontsov@ru.mvista.com>
---

On Fri, Jan 30, 2009 at 12:57:01PM -0500, Steven Rostedt wrote:
[...]
> > > Turn on CONFIG_PREEMPT_TRACE (not TRACER) and it should show the
> > > location that left preemption disabled.
> >
> > Thank you Steven, PREEMPT_TRACE is a great tool indeed (though on
> > PowerPC it doesn't work out of the box, but easily fixable).
>
> Cool, I'd be interested in those fixes.

Here it is. "ftrace: On PowerPC we don't need frame pointers for
CALLER_ADDRs" patch (http://lkml.org/lkml/2009/1/31/141) is also
needed for this to work.

Thanks,

arch/powerpc/kernel/process.c | 4 +++-
1 files changed, 3 insertions(+), 1 deletions(-)

diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index 957bded..b8642bf 100644
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -1020,7 +1020,7 @@ void show_stack(struct task_struct *tsk, unsigned long *stack)
printk("Call Trace:\n");
do {
if (!validate_sp(sp, tsk, STACK_FRAME_OVERHEAD))
- return;
+ goto out;

stack = (unsigned long *) sp;
newsp = stack[0];
@@ -1049,6 +1049,8 @@ void show_stack(struct task_struct *tsk, unsigned long *stack)

sp = newsp;
} while (count++ < kstack_depth_to_print);
+out:
+ print_preempt_trace(tsk);
}

void dump_stack(void)
--
1.5.6.5