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powerpc/ftrace: Do not trace restore_interrupts()

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As I was adding code that affects all archs, I started testing function
tracer against PPC64 and found that it currently locks up with 3.4
kernel. I figured it was due to tracing a function that shouldn't be, so
I went through the following process to bisect to find the culprit:

 cat /debug/tracing/available_filter_functions > t
 num=`wc -l t`
 sed -ne "1,${num}p" t > t1
 let num=num+1
 sed -ne "${num},$p" t > t2
 cat t1 > /debug/tracing/set_ftrace_filter
 echo function /debug/tracing/current_tracer
 <failed? bisect t1, if not bisect t2>

It finally came down to this function: restore_interrupts()

I'm not sure why this locks up the system. It just seems to prevent
scheduling from occurring. Interrupts seem to still work, as I can ping
the box. But all user processes freeze.

When restore_interrupts() is not traced, function tracing works fine.

Cc: stable@kernel.org
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
This commit is contained in:
Steven Rostedt 2012-06-04 16:27:54 +00:00 committed by Benjamin Herrenschmidt
parent 2cb387ae75
commit 2d773aa481
1 changed files with 1 additions and 1 deletions
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arch/powerpc/kernel/irq.c
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@ -277,7 +277,7 @@ EXPORT_SYMBOL(arch_local_irq_restore);
* NOTE: This is called with interrupts hard disabled but not marked
* as such in paca->irq_happened, so we need to resync this.
*/
void restore_interrupts(void)
void notrace restore_interrupts(void)
{
if (irqs_disabled()) {
local_paca->irq_happened |= PACA_IRQ_HARD_DIS;