On Mon, 2019-01-07 at 11:26 +0100, Peter Zijlstra wrote: > > I would expect lockdep you also complain about this...
And grumble it did. commit df7e8acc0c9a84979a448d215b8ef889efe4ac5a Author: Mike Galbraith <[email protected]> Date: Fri May 4 08:14:38 2018 +0200 sched/fair: Fix CFS bandwidth control lockdep DEADLOCK report CFS bandwidth control yields the inversion gripe below, moving handling quells it. |======================================================== |WARNING: possible irq lock inversion dependency detected |4.16.7-rt1-rt #2 Tainted: G E |-------------------------------------------------------- |sirq-hrtimer/0/15 just changed the state of lock: | (&cfs_b->lock){+...}, at: [<000000009adb5cf7>] sched_cfs_period_timer+0x28/0x140 |but this lock was taken by another, HARDIRQ-safe lock in the past: (&rq->lock){-...} |and interrupts could create inverse lock ordering between them. |other info that might help us debug this: | Possible interrupt unsafe locking scenario: | CPU0 CPU1 | ---- ---- | lock(&cfs_b->lock); | local_irq_disable(); | lock(&rq->lock); | lock(&cfs_b->lock); | <Interrupt> | lock(&rq->lock); Cc: [email protected] Acked-by: Steven Rostedt (VMware) <[email protected]> Signed-off-by: Mike Galbraith <[email protected]> Signed-off-by: Sebastian Andrzej Siewior <[email protected]> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 960ad0ce77d7..420624c49f38 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -5007,9 +5007,9 @@ void init_cfs_bandwidth(struct cfs_bandwidth *cfs_b) cfs_b->period = ns_to_ktime(default_cfs_period()); INIT_LIST_HEAD(&cfs_b->throttled_cfs_rq); - hrtimer_init(&cfs_b->period_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_PINNED); + hrtimer_init(&cfs_b->period_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_PINNED_HARD); cfs_b->period_timer.function = sched_cfs_period_timer; - hrtimer_init(&cfs_b->slack_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); + hrtimer_init(&cfs_b->slack_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL_HARD); cfs_b->slack_timer.function = sched_cfs_slack_timer; }
