Because the sched_class::put_prev_task() callback of rt and fair classes are referring to the rq clock to update their runtime statistics. A CPU running in tickless mode may carry a stale value. We need to update it there.
Signed-off-by: Frederic Weisbecker <[email protected]> Cc: Alessio Igor Bogani <[email protected]> Cc: Andrew Morton <[email protected]> Cc: Chris Metcalf <[email protected]> Cc: Christoph Lameter <[email protected]> Cc: Geoff Levand <[email protected]> Cc: Gilad Ben Yossef <[email protected]> Cc: Hakan Akkan <[email protected]> Cc: Ingo Molnar <[email protected]> Cc: Li Zhong <[email protected]> Cc: Namhyung Kim <[email protected]> Cc: Paul E. McKenney <[email protected]> Cc: Paul Gortmaker <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Steven Rostedt <[email protected]> Cc: Thomas Gleixner <[email protected]> Cc: Paul Turner <[email protected]> Cc: Mike Galbraith <[email protected]> --- kernel/sched/core.c | 7 +++++++ kernel/sched/sched.h | 7 +++++++ 2 files changed, 14 insertions(+), 0 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index e91ee58..1826e00 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -4946,6 +4946,13 @@ static void migrate_tasks(unsigned int dead_cpu) */ rq->stop = NULL; + /* + * put_prev_task() and pick_next_task() sched + * class method both need to have an up-to-date + * value of rq->clock[_task] + */ + update_nohz_rq_clock(rq); + for ( ; ; ) { /* * There's this thread running, bail when that's the only diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index 3bd15a4..96f7333 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -5,6 +5,7 @@ #include <linux/mutex.h> #include <linux/spinlock.h> #include <linux/stop_machine.h> +#include <linux/tick.h> #include "cpupri.h" @@ -1115,6 +1116,12 @@ static inline void dec_nr_running(struct rq *rq) extern void update_rq_clock(struct rq *rq); +static inline void update_nohz_rq_clock(struct rq *rq) +{ + if (tick_nohz_extended_cpu(cpu_of(rq))) + update_rq_clock(rq); +} + extern void activate_task(struct rq *rq, struct task_struct *p, int flags); extern void deactivate_task(struct rq *rq, struct task_struct *p, int flags); -- 1.7.5.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
