From: Kirill Tkhai <[email protected]> Since calc_load_fold_active() reads two variables (nr_running and nr_uninterruptible) it may race with parallel try_to_wake_up(). So it must be executed under rq::lock to prevent that. This seems to be the reason of negative calc_load_tasks, observed on several machines.
https://jira.sw.ru/browse/PSBM-68052 Signed-off-by: Kirill Tkhai <[email protected]> (cherry-picked from vz7 commit 63138412c98b7db9252b78efd7e6e86d11d5111d) Rebase to vz8: - move calc_load_migrate under rq lock - move the rq lock/unlock hunk from calc_load_enter_idle() to calc_load_nohz_start() - use rq_(un)lock helpers like in patch sent to ms https://lkml.org/lkml/2017/7/7/472 This patch did not hit mainstream for some reason but it is likely still valid, at least I don't see any explicit fix of this problem. https://jira.sw.ru/browse/PSBM-127780 Signed-off-by: Pavel Tikhomirov <[email protected]> --- kernel/sched/core.c | 2 +- kernel/sched/loadavg.c | 6 +++++- 2 files changed, 6 insertions(+), 2 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 375de135c1320..3878a91a54b5f 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -6153,9 +6153,9 @@ int sched_cpu_dying(unsigned int cpu) } migrate_tasks(rq, &rf); BUG_ON(rq->nr_running != 1); + calc_load_migrate(rq); rq_unlock_irqrestore(rq, &rf); - calc_load_migrate(rq); update_max_interval(); nohz_balance_exit_idle(rq); hrtick_clear(rq); diff --git a/kernel/sched/loadavg.c b/kernel/sched/loadavg.c index c2aab7d55ff23..618682402a3f2 100644 --- a/kernel/sched/loadavg.c +++ b/kernel/sched/loadavg.c @@ -312,11 +312,15 @@ static void calc_load_nohz_fold(struct rq *rq) void calc_load_nohz_start(void) { + struct rq *rq = this_rq(); + struct rq_flags rf; /* * We're going into NO_HZ mode, if there's any pending delta, fold it * into the pending NO_HZ delta. */ - calc_load_nohz_fold(this_rq()); + rq_lock(rq, &rf); + calc_load_nohz_fold(rq); + rq_unlock(rq, &rf); } /* -- 2.30.2 _______________________________________________ Devel mailing list [email protected] https://lists.openvz.org/mailman/listinfo/devel
