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