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.
Hi Doug,
could you elaborate ? I don't get the 'because the MCT ... slow'
Thanks
-- Daniel
Signed-off-by: Doug Anderson <dianders@xxxxxxxxxxxx>
---
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)
{
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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