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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>
This commit is contained in:
Steven Rostedt (VMware) 2018-04-04 14:50:15 -04:00
parent 927e56db62
commit f7a1570da9
1 changed files with 2 additions and 2 deletions
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4
kernel/trace/trace_clock.c
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@ -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;
}