Messages in this thread Patch in this message | | | Subject | Re: [RFC/PATCH] Prevent wasting time to find out get_parent_ip | From | Steven Rostedt <> | Date | Tue, 24 Apr 2012 14:16:37 -0400 |
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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!
> 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
> #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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