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 <rost...@goodmis.org>
Cc: Ingo Molnar <mi...@redhat.com>
Signed-off-by: Jerry Snitselaar <jsnit...@redhat.com>
---
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();
}
+EXPORT_SYMBOL_GPL(trace_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);
}
+EXPORT_SYMBOL_GPL(trace_clock_jiffies);
/*
* trace_clock_global(): special globally coherent trace clock
@@ -123,6 +125,7 @@ u64 notrace trace_clock_global(void)
return now;
}
+EXPORT_SYMBOL_GPL(trace_clock_global);
static atomic64_t trace_counter;
--
2.4.0.rc3.3.g6eb1401
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