linux-kernel - [PATCH -rt] powerpc/tracing: Add support for "PREEMPT

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Date:	Sat, 31 Jan 2009 22:14:44 +0300
From:	Anton Vorontsov <avorontsov@...mvista.com>
To:	Steven Rostedt <srostedt@...hat.com>, Ingo Molnar <mingo@...e.hu>
Cc:	Paul Mackerras <paulus@...ba.org>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	linuxppc-dev@...abs.org, linux-kernel@...r.kernel.org,
	linux-rt-users@...r.kernel.org
Subject: [PATCH -rt] powerpc/tracing: Add support for "PREEMPT_TRACE" tracer

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@...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
--
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