[PATCH v2] tracing: Export tracing clock functions

From: Jerry Snitselaar
Date: Thu Apr 30 2015 - 11:10:31 EST

Critical tracepoint hooks should never call anything that takes a lock,
so they are unable to call getrawmonotonic() or ktime_get().

Export the rest of the tracing clock functions so can be used in
tracepoint hooks.

Background: We have a customer that adds their own module and registers
a tracepoint hook to sched_wakeup. They were using ktime_get() for a
time source, but it grabs a seq lock and caused a deadlock to occur.

v2: added background info and fixed typo

Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Signed-off-by: Jerry Snitselaar <jsnitsel@xxxxxxxxxx>
kernel/trace/trace_clock.c | 3 +++
1 file changed, 3 insertions(+)

diff --git a/kernel/trace/trace_clock.c b/kernel/trace/trace_clock.c
index 57b67b1..0f06532 100644
--- a/kernel/trace/trace_clock.c
+++ b/kernel/trace/trace_clock.c
@@ -56,6 +56,7 @@ u64 notrace trace_clock(void)
return local_clock();

* trace_jiffy_clock(): Simply use jiffies as a clock counter.
@@ -68,6 +69,7 @@ u64 notrace trace_clock_jiffies(void)
return jiffies_64_to_clock_t(jiffies_64 - INITIAL_JIFFIES);

* trace_clock_global(): special globally coherent trace clock
@@ -123,6 +125,7 @@ u64 notrace trace_clock_global(void)

return now;

static atomic64_t trace_counter;


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