From d60585c5766e9620d5d83e2b25dc042c7bdada2c Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Tue, 12 Jul 2016 18:33:56 +0200 Subject: sched/core: Correct off by one bug in load migration calculation The move of calc_load_migrate() from CPU_DEAD to CPU_DYING did not take into account that the function is now called from a thread running on the outgoing CPU. As a result a cpu unplug leakes a load of 1 into the global load accounting mechanism. Fix it by adjusting for the currently running thread which calls calc_load_migrate(). Reported-by: Anton Blanchard Signed-off-by: Thomas Gleixner Acked-by: Peter Zijlstra Cc: Linus Torvalds Cc: Michael Ellerman Cc: Vaidyanathan Srinivasan Cc: rt@linutronix.de Cc: shreyas@linux.vnet.ibm.com Fixes: e9cd8fa4fcfd: ("sched/migration: Move calc_load_migrate() into CPU_DYING") Link: http://lkml.kernel.org/r/alpine.DEB.2.11.1607121744350.4083@nanos Signed-off-by: Ingo Molnar --- kernel/sched/core.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) (limited to 'kernel/sched/core.c') diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 51d7105f529a..97ee9ac7e97c 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -5394,13 +5394,15 @@ void idle_task_exit(void) /* * Since this CPU is going 'away' for a while, fold any nr_active delta * we might have. Assumes we're called after migrate_tasks() so that the - * nr_active count is stable. + * nr_active count is stable. We need to take the teardown thread which + * is calling this into account, so we hand in adjust = 1 to the load + * calculation. * * Also see the comment "Global load-average calculations". */ static void calc_load_migrate(struct rq *rq) { - long delta = calc_load_fold_active(rq); + long delta = calc_load_fold_active(rq, 1); if (delta) atomic_long_add(delta, &calc_load_tasks); } -- cgit v1.2.3