sched: sched_clock() improvement: use in_nmi()

make sure we dont execute more complex sched_clock() code in NMI context.

Acked-by: Peter Zijlstra <peterz@infradead.org>
Acked-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

diff --git a/kernel/sched_clock.c b/kernel/sched_clock.c
index a0b0852414cc599169efd81c5789f03ee50dad8b..db69174b11784016d82dd1b0b3baad9d28c274fc 100644 (file)
--- a/kernel/sched_clock.c
+++ b/kernel/sched_clock.c
@@ -29,6 +29,7 @@
 #include <linux/spinlock.h>
 #include <linux/ktime.h>
 #include <linux/module.h>
+#include <linux/hardirq.h>
 
 /*
  * Scheduler clock - returns current time in nanosec units.
@@ -151,6 +152,13 @@ u64 sched_clock_cpu(int cpu)
        struct sched_clock_data *scd = cpu_sdc(cpu);
        u64 now, clock, this_clock, remote_clock;
 
+       /*
+        * Normally this is not called in NMI context - but if it is,
+        * trying to do any locking here is totally lethal.
+        */
+       if (unlikely(in_nmi()))
+               return scd->clock;
+
        if (unlikely(!sched_clock_running))
                return 0ull;