Messages in this thread | | | Date | Wed, 25 Apr 2012 08:54:19 +0900 | From | Minho Ban <> | Subject | Re: [RFC/PATCH] Prevent wasting time to find out get_parent_ip |
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On 04/25/2012 03:16 AM, Steven Rostedt wrote: > On Tue, 2012-04-24 at 21:36 +0900, Minho Ban wrote: >> trace_preempt_on/off looks empty if PREEMPT_TRACER is off. But actually it is >> spending time to find out get_parent_ip(even CALLER_ADDR for some ARCH) which is >> in argument. This seems not fair for those who expect to do nothing but increase >> or decrease count. >> > > Yuck what an ugly patch. Please don't uglify the C code with #ifdefs! >
Yes, I agree.
>> Cc: Thomas Gleixner <tglx@linutronix.de> >> Signed-off-by: Minho Ban <mhban@samsung.com> >> --- >> include/linux/ftrace.h | 3 --- >> kernel/sched/core.c | 5 ++++- >> kernel/softirq.c | 3 ++- >> 3 files changed, 6 insertions(+), 5 deletions(-) >> >> diff --git a/include/linux/ftrace.h b/include/linux/ftrace.h >> index 72a6cab..7cd11fe 100644 >> --- a/include/linux/ftrace.h >> +++ b/include/linux/ftrace.h >> @@ -484,9 +484,6 @@ static inline void __ftrace_enabled_restore(int enabled) >> #ifdef CONFIG_PREEMPT_TRACER >> extern void trace_preempt_on(unsigned long a0, unsigned long a1); >> extern void trace_preempt_off(unsigned long a0, unsigned long a1); >> -#else >> - static inline void trace_preempt_on(unsigned long a0, unsigned long a1) { } >> - static inline void trace_preempt_off(unsigned long a0, unsigned long a1) { } > > If you want to hide the "CALLER_ADDR" for other archs, then simply do: > > # define trace_preempt_on(a0, a1) do { } while (0) > # define trace_preempt_off(a0, a1) do { } while (0) > > and be done with it. > > Oh, you should add a comment before these defines to the effect of: > > /* > * Use defines instead of static inlines because some arches will make > * code out of the CALLER_ADDR, when we really want these to be a real > * nop. > */ > > That way, you will document why we use defines instead of static > inlines. > > -- Steve >
Very appreciate your explanation and detailed(even complete) sample code. I'll apply your code.
>> #endif >> >> #ifdef CONFIG_FTRACE_MCOUNT_RECORD >> diff --git a/kernel/sched/core.c b/kernel/sched/core.c >> index 4603b9d..efdd5a0 100644 >> --- a/kernel/sched/core.c >> +++ b/kernel/sched/core.c >> @@ -3068,8 +3068,10 @@ void __kprobes add_preempt_count(int val) >> DEBUG_LOCKS_WARN_ON((preempt_count() & PREEMPT_MASK) >= >> PREEMPT_MASK - 10); >> #endif >> +#ifdef CONFIG_PREEMPT_TRACER >> if (preempt_count() == val) >> trace_preempt_off(CALLER_ADDR0, get_parent_ip(CALLER_ADDR1)); >> +#endif >> } >> EXPORT_SYMBOL(add_preempt_count); >> >> @@ -3088,9 +3090,10 @@ void __kprobes sub_preempt_count(int val) >> !(preempt_count() & PREEMPT_MASK))) >> return; >> #endif >> - >> +#ifdef CONFIG_PREEMPT_TRACER >> if (preempt_count() == val) >> trace_preempt_on(CALLER_ADDR0, get_parent_ip(CALLER_ADDR1)); >> +#endif >> preempt_count() -= val; >> } >> EXPORT_SYMBOL(sub_preempt_count); >> diff --git a/kernel/softirq.c b/kernel/softirq.c >> index 671f959..e7c8336 100644 >> --- a/kernel/softirq.c >> +++ b/kernel/softirq.c >> @@ -112,9 +112,10 @@ static void __local_bh_disable(unsigned long ip, unsigned int cnt) >> if (softirq_count() == cnt) >> trace_softirqs_off(ip); >> raw_local_irq_restore(flags); >> - >> +#ifdef CONFIG_PREEMPT_TRACER >> if (preempt_count() == cnt) >> trace_preempt_off(CALLER_ADDR0, get_parent_ip(CALLER_ADDR1)); >> +#endif >> } >> #else /* !CONFIG_TRACE_IRQFLAGS */ >> static inline void __local_bh_disable(unsigned long ip, unsigned int cnt) > > >
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