sched: add [__]update_rq_clock(rq)

add the [__]update_rq_clock(rq) functions. (No change in functionality,
just reorganization to prepare for elimination of the heavy 64-bit
timestamp-passing in the scheduler.)

Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 22 insertions, 8 deletions

diff --git a/kernel/sched.c b/kernel/sched.c
index 1fa07c14624e..d613723f324f 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -318,15 +318,19 @@ static inline int cpu_of(struct rq *rq)
 }
 
 /*
- * Per-runqueue clock, as finegrained as the platform can give us:
+ * Update the per-runqueue clock, as finegrained as the platform can give
+ * us, but without assuming monotonicity, etc.:
  */
-static unsigned long long __rq_clock(struct rq *rq)
+static void __update_rq_clock(struct rq *rq)
 {
         u64 prev_raw = rq->prev_clock_raw;
         u64 now = sched_clock();
         s64 delta = now - prev_raw;
         u64 clock = rq->clock;
 
+#ifdef CONFIG_SCHED_DEBUG
+        WARN_ON_ONCE(cpu_of(rq) != smp_processor_id());
+#endif
         /*
          * Protect against sched_clock() occasionally going backwards:
          */
@@ -349,17 +353,24 @@ static unsigned long long __rq_clock(struct rq *rq)
 
         rq->prev_clock_raw = now;
         rq->clock = clock;
+}
 
-        return clock;
+static void update_rq_clock(struct rq *rq)
+{
+        if (likely(smp_processor_id() == cpu_of(rq)))
+                __update_rq_clock(rq);
 }
 
-static unsigned long long rq_clock(struct rq *rq)
+static u64 __rq_clock(struct rq *rq)
 {
-        int this_cpu = smp_processor_id();
+        __update_rq_clock(rq);
 
-        if (this_cpu == cpu_of(rq))
-                return __rq_clock(rq);
+        return rq->clock;
+}
 
+static u64 rq_clock(struct rq *rq)
+{
+        update_rq_clock(rq);
         return rq->clock;
 }
 
@@ -386,9 +397,12 @@ unsigned long long cpu_clock(int cpu)
 {
         unsigned long long now;
         unsigned long flags;
+        struct rq *rq;
 
         local_irq_save(flags);
-        now = rq_clock(cpu_rq(cpu));
+        rq = cpu_rq(cpu);
+        update_rq_clock(rq);
+        now = rq->clock;
         local_irq_restore(flags);
 
         return now;