[PATCH] sched: generalize CONFIG_IRQ_TIME_ACCOUNTING for X86 and ARM

On 02/27/2012 02:12 PM, Peter Zijlstra wrote:

quoted

-extern void enable_sched_clock_irqtime(void);
-extern void disable_sched_clock_irqtime(void);
+extern int sched_clock_irqtime;
+static inline void enable_sched_clock_irqtime(void)
+{
+	if (sched_clock_irqtime == -1)
+		sched_clock_irqtime = 1;
+}
+static inline void disable_sched_clock_irqtime(void)
+{
+	sched_clock_irqtime = 0;
+}
  #else
  static inline void enable_sched_clock_irqtime(void) {}
  static inline void disable_sched_clock_irqtime(void) {}

Please keep them out-of-line, its not a fast path and it avoids having
to expose the state variable.

OK

quoted

+/*
+ * -1 if not initialized, 0 if disabled with "noirqtime" kernel option
+ * or after unstable clock was detected, 1 if enabled and active.
+ */

You forgot to explain what you need the tri-state for.

quoted

+__read_mostly int sched_clock_irqtime = -1;

The comment above should be a sufficient explanation, isn't it?

It's a tri-state just because it "merges" two variables: internal state (enabled/disabled)
and the value passed by "noirqtime" option (turn it on, default/turn it off). It can be
enabled only if it was not turned off explicitly, i.e. -1 => 1 transition is possible,
but 0 -> 1 is not. The same rule applies to a situation when an unstable clock is detected.

Dmitry