On 02/27/2012 02:12 PM, Peter Zijlstra wrote:
-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
+/*
+ * -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.
+__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
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