tracing: Hide global trace clock from lockdep

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@gandalf.local.home
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

diff --git a/kernel/trace/trace_clock.c b/kernel/trace/trace_clock.c
index 5fdc779f411d83f5f47d5f501b0c0b8cc40facca..d8a188e0418aa9ad31798d9fb5cb3320a409d1b2 100644 (file)
--- 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)
        arch_spin_unlock(&trace_clock_struct.lock);
 
  out:
-       local_irq_restore(flags);
+       raw_local_irq_restore(flags);
 
        return now;
 }