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tracing, x86/irq: Do not trace arch_local_{*,irq_*}() functions

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I triggered a triple fault with gcc 4.5.1 because it did not
honor the inline annotation to arch_local_save_flags() function
and that function was added to the pool of functions traced by
the function tracer.

When preempt_schedule() called arch_local_save_flags() (called
by irqs_disabled()), it was traced, but the first thing the
function tracer does is disable preemption. When it enables
preemption, the NEED_RESCHED flag will not have been cleared and
the preemption check will trigger the call to preempt_schedule()
again.

Although the dynamic function tracer crashed immediately, the
static version of the function tracer (CONFIG_DYNAMIC_FTRACE is
not set) actually was able to show where the problem was.

 swapper-1       3.N.. 103885us : arch_local_save_flags <-preempt_schedule
 swapper-1       3.N.. 103886us : arch_local_save_flags <-preempt_schedule
 swapper-1       3.N.. 103886us : arch_local_save_flags <-preempt_schedule
 swapper-1       3.N.. 103887us : arch_local_save_flags <-preempt_schedule
 swapper-1       3.N.. 103887us : arch_local_save_flags <-preempt_schedule
 swapper-1       3.N.. 103888us : arch_local_save_flags <-preempt_schedule
 swapper-1       3.N.. 103888us : arch_local_save_flags <-preempt_schedule

It went on for a while before it triple faulted with a corrupted
stack.

The arch_local_save_flags and arch_local_irq_* functions should
not be traced. Even though they are marked as inline, gcc may
still make them a function and enable tracing of them.

The simple solution is to just mark them as notrace. I had to
add the <linux/types.h> for this file to include the notrace
tag.

Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Link: http://lkml.kernel.org/r/20110702033852.733414762@goodmis.org
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Steven Rostedt 2011-07-01 23:04:36 -04:00 committed by Ingo Molnar
parent 931da6137e
commit e08fbb78f0
1 changed files with 6 additions and 5 deletions
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11
arch/x86/include/asm/irqflags.h
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@ -60,23 +60,24 @@ static inline void native_halt(void)
#include <asm/paravirt.h>
#else
#ifndef __ASSEMBLY__
#include <linux/types.h>
static inline unsigned long arch_local_save_flags(void)
static inline notrace unsigned long arch_local_save_flags(void)
{
return native_save_fl();
}
static inline void arch_local_irq_restore(unsigned long flags)
static inline notrace void arch_local_irq_restore(unsigned long flags)
{
native_restore_fl(flags);
}
static inline void arch_local_irq_disable(void)
static inline notrace void arch_local_irq_disable(void)
{
native_irq_disable();
}
static inline void arch_local_irq_enable(void)
static inline notrace void arch_local_irq_enable(void)
{
native_irq_enable();
}
@ -102,7 +103,7 @@ static inline void halt(void)
/*
* For spinlocks, etc:
*/
static inline unsigned long arch_local_irq_save(void)
static inline notrace unsigned long arch_local_irq_save(void)
{
unsigned long flags = arch_local_save_flags();
arch_local_irq_disable();