Gitweb:
http://git.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=20d315d42aed95423a7203e1d7e84086004b5a00
Commit: 20d315d42aed95423a7203e1d7e84086004b5a00
Parent: 6aa645ea5f7a246702e07f29edc7075d487ae4a3
Author: Ingo Molnar <[EMAIL PROTECTED]>
AuthorDate: Mon Jul 9 18:51:58 2007 +0200
Committer: Ingo Molnar <[EMAIL PROTECTED]>
CommitDate: Mon Jul 9 18:51:58 2007 +0200
sched: add rq_clock()/__rq_clock()
add rq_clock()/__rq_clock(), a robust wrapper around sched_clock(),
used by CFS. It protects against common type of sched_clock() problems
(caused by hardware): time warps forwards and backwards.
Signed-off-by: Ingo Molnar <[EMAIL PROTECTED]>
---
kernel/sched.c | 46 ++++++++++++++++++++++++++++++++++++++++++++++
1 files changed, 46 insertions(+), 0 deletions(-)
diff --git a/kernel/sched.c b/kernel/sched.c
index 085418b..29eb227 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -389,6 +389,52 @@ static inline int cpu_of(struct rq *rq)
}
/*
+ * Per-runqueue clock, as finegrained as the platform can give us:
+ */
+static unsigned long long __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;
+
+ /*
+ * Protect against sched_clock() occasionally going backwards:
+ */
+ if (unlikely(delta < 0)) {
+ clock++;
+ rq->clock_warps++;
+ } else {
+ /*
+ * Catch too large forward jumps too:
+ */
+ if (unlikely(delta > 2*TICK_NSEC)) {
+ clock++;
+ rq->clock_overflows++;
+ } else {
+ if (unlikely(delta > rq->clock_max_delta))
+ rq->clock_max_delta = delta;
+ clock += delta;
+ }
+ }
+
+ rq->prev_clock_raw = now;
+ rq->clock = clock;
+
+ return clock;
+}
+
+static inline unsigned long long rq_clock(struct rq *rq)
+{
+ int this_cpu = smp_processor_id();
+
+ if (this_cpu == cpu_of(rq))
+ return __rq_clock(rq);
+
+ return rq->clock;
+}
+
+/*
* The domain tree (rq->sd) is protected by RCU's quiescent state transition.
* See detach_destroy_domains: synchronize_sched for details.
*
-
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