Messages in this thread | | | Date | Tue, 17 Jun 2014 14:13:15 +0200 | From | Daniel Lezcano <> | Subject | Re: [PATCH 1/3] clocksource: exynos_mct: Fix ftrace |
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On 06/04/2014 07:30 PM, Doug Anderson wrote: > In (93bfb76 clocksource: exynos_mct: register sched_clock callback) we > supported using the MCT as a scheduler clock. We properly marked > exynos4_read_sched_clock() as notrace. However, we then went and > called another function that _wasn't_ notrace. That means if you do: > > cd /sys/kernel/debug/tracing/ > echo function_graph > current_tracer > > You'll get a crash. > > Fix this (but still let other readers of the MCT be trace-enabled) by > adding an extra function. It's important to keep other users of MCT > traceable because the MCT is actually quite slow.
Thanks for the explanation in the other email.
I think the last sentence is a bit confusing because you are implicitly saying you need these traces to investigate why the timer is slow which is referring to something not related to this fix.
> Signed-off-by: Doug Anderson <dianders@chromium.org> > --- > drivers/clocksource/exynos_mct.c | 9 +++++++-- > 1 file changed, 7 insertions(+), 2 deletions(-) > > diff --git a/drivers/clocksource/exynos_mct.c b/drivers/clocksource/exynos_mct.c > index 8d64200..ba3a683 100644 > --- a/drivers/clocksource/exynos_mct.c > +++ b/drivers/clocksource/exynos_mct.c > @@ -165,7 +165,7 @@ static void exynos4_mct_frc_start(u32 hi, u32 lo) > exynos4_mct_write(reg, EXYNOS4_MCT_G_TCON); > } > > -static cycle_t exynos4_frc_read(struct clocksource *cs) > +static inline cycle_t notrace _exynos4_frc_read(void)
Why inline ?
> { > unsigned int lo, hi; > u32 hi2 = __raw_readl(reg_base + EXYNOS4_MCT_G_CNT_U); > @@ -179,6 +179,11 @@ static cycle_t exynos4_frc_read(struct clocksource *cs) > return ((cycle_t)hi << 32) | lo; > } > > +static cycle_t exynos4_frc_read(struct clocksource *cs) > +{ > + return _exynos4_frc_read(); > +} > + > static void exynos4_frc_resume(struct clocksource *cs) > { > exynos4_mct_frc_start(0, 0); > @@ -195,7 +200,7 @@ struct clocksource mct_frc = { > > static u64 notrace exynos4_read_sched_clock(void) > { > - return exynos4_frc_read(&mct_frc); > + return _exynos4_frc_read(); > } > > static void __init exynos4_clocksource_init(void) >
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