[for-next][PATCH 15/18] tracing: Hide global trace clock from lockdep

From: Steven Rostedt
Date: Fri Apr 06 2018 - 09:03:34 EST

From: "Steven Rostedt (VMware)" <rostedt@xxxxxxxxxxx>

Function tracing can trace in NMIs and such. If the TSC is determined
to be unstable, the tracing clock will switch to the global clock on
boot up, unless "trace_clock" is specified on the kernel command line.

The global clock disables interrupts to access sched_clock_cpu(), and in
doing so can be done within lockdep internals (because of function
tracing and NMIs). This can trigger false lockdep splats.

The trace_clock_global() is special, best not to trace the irq logic
within it.

Link: http://lkml.kernel.org/r/20180404145015.77bde42d@xxxxxxxxxxxxxxxxxx

Signed-off-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
kernel/trace/trace_clock.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/trace/trace_clock.c b/kernel/trace/trace_clock.c
index 5fdc779f411d..d8a188e0418a 100644
--- a/kernel/trace/trace_clock.c
+++ b/kernel/trace/trace_clock.c
@@ -96,7 +96,7 @@ u64 notrace trace_clock_global(void)
int this_cpu;
u64 now;

- local_irq_save(flags);
+ raw_local_irq_save(flags);

this_cpu = raw_smp_processor_id();
now = sched_clock_cpu(this_cpu);
@@ -122,7 +122,7 @@ u64 notrace trace_clock_global(void)

- local_irq_restore(flags);
+ raw_local_irq_restore(flags);

return now;