From 61eadef6a9bde9ea62fda724a9cb501ce9bc925a Mon Sep 17 00:00:00 2001 From: Mike Galbraith Date: Fri, 29 Apr 2011 08:36:50 +0200 Subject: [PATCH] sched, rt: Update rq clock when unthrottling of an otherwise idle CPU If an RT task is awakened while it's rt_rq is throttled, the time between wakeup/enqueue and unthrottle/selection may be accounted as rt_time if the CPU is idle. Set rq->skip_clock_update negative upon throttle release to tell put_prev_task() that we need a clock update. Reported-by: Thomas Giesel Signed-off-by: Mike Galbraith Signed-off-by: Peter Zijlstra Link: http://lkml.kernel.org/r/1304059010.7472.1.camel@marge.simson.net Signed-off-by: Ingo Molnar --- kernel/sched.c | 6 +++--- kernel/sched_rt.c | 7 +++++++ 2 files changed, 10 insertions(+), 3 deletions(-) diff --git a/kernel/sched.c b/kernel/sched.c index f9778c0..b8b9a7d 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -466,7 +466,7 @@ struct rq { u64 nohz_stamp; unsigned char nohz_balance_kick; #endif - unsigned int skip_clock_update; + int skip_clock_update; /* capture load from *all* tasks on this cpu: */ struct load_weight load; @@ -652,7 +652,7 @@ static void update_rq_clock(struct rq *rq) { s64 delta; - if (rq->skip_clock_update) + if (rq->skip_clock_update > 0) return; delta = sched_clock_cpu(cpu_of(rq)) - rq->clock; @@ -4127,7 +4127,7 @@ static inline void schedule_debug(struct task_struct *prev) static void put_prev_task(struct rq *rq, struct task_struct *prev) { - if (prev->on_rq) + if (prev->on_rq || rq->skip_clock_update < 0) update_rq_clock(rq); prev->sched_class->put_prev_task(rq, prev); } diff --git a/kernel/sched_rt.c b/kernel/sched_rt.c index 19ecb31..0943ed7 100644 --- a/kernel/sched_rt.c +++ b/kernel/sched_rt.c @@ -562,6 +562,13 @@ static int do_sched_rt_period_timer(struct rt_bandwidth *rt_b, int overrun) if (rt_rq->rt_throttled && rt_rq->rt_time < runtime) { rt_rq->rt_throttled = 0; enqueue = 1; + + /* + * Force a clock update if the CPU was idle, + * lest wakeup -> unthrottle time accumulate. + */ + if (rt_rq->rt_nr_running && rq->curr == rq->idle) + rq->skip_clock_update = -1; } if (rt_rq->rt_time || rt_rq->rt_nr_running) idle = 0; -- 2.7.4