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tracing: Hide global trace clock from lockdep

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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;
}