Re: [PATCH] sched/deadline: Add missing update_rq_clock() in dl_task_timer()

Juri Lelli
2017-03-15T11:03:03Z

Hi,

On 06/03/17 21:51, Wanpeng Li wrote:
> From: Wanpeng Li <wanpeng.li@hotmail.com>
>
> The following warning can be triggered by hot-unplugging the CPU
> on which an active SCHED_DEADLINE task is running on:
>
> ------------[ cut here ]------------
> WARNING: CPU: 7 PID: 0 at kernel/sched/sched.h:833 replenish_dl_entity+0x71e/0xc40
> rq->clock_update_flags < RQCF_ACT_SKIP
> CPU: 7 PID: 0 Comm: swapper/7 Tainted: G B 4.11.0-rc1+ #24
> Hardware name: LENOVO ThinkCentre M8500t-N000/SHARKBAY, BIOS FBKTC1AUS 02/16/2016
> Call Trace:
> <IRQ>
> dump_stack+0x85/0xc4
> __warn+0x172/0x1b0
> warn_slowpath_fmt+0xb4/0xf0
> ? __warn+0x1b0/0x1b0
> ? debug_check_no_locks_freed+0x2c0/0x2c0
> ? cpudl_set+0x3d/0x2b0
> replenish_dl_entity+0x71e/0xc40
> enqueue_task_dl+0x2ea/0x12e0
> ? dl_task_timer+0x777/0x990
> ? __hrtimer_run_queues+0x270/0xa50
> dl_task_timer+0x316/0x990
> ? enqueue_task_dl+0x12e0/0x12e0
> ? enqueue_task_dl+0x12e0/0x12e0
> __hrtimer_run_queues+0x270/0xa50
> ? hrtimer_cancel+0x20/0x20
> ? hrtimer_interrupt+0x119/0x600
> hrtimer_interrupt+0x19c/0x600
> ? trace_hardirqs_off+0xd/0x10
> local_apic_timer_interrupt+0x74/0xe0
> smp_apic_timer_interrupt+0x76/0xa0
> apic_timer_interrupt+0x93/0xa0
>
> The DL task will be migrated to a suitable later deadline rq once the DL
> timer fires and currnet rq is offline. The rq clock of the new rq should
> be updated. This patch fixes it by updating the rq clock after holding
> the new rq's rq lock.
>
> Cc: Juri Lelli <juri.lelli@arm.com>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Ingo Molnar <mingo@kernel.org>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Matt Fleming <matt@codeblueprint.co.uk>
> Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com>
> ---
> kernel/sched/deadline.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
> index 99b2c33..c6db3fd 100644
> --- a/kernel/sched/deadline.c
> +++ b/kernel/sched/deadline.c
> @@ -638,6 +638,7 @@ static enum hrtimer_restart dl_task_timer(struct hrtimer *timer)
> lockdep_unpin_lock(&rq->lock, rf.cookie);
> rq = dl_task_offline_migration(rq, p);
> rf.cookie = lockdep_pin_lock(&rq->lock);
> + update_rq_clock(rq);

Looks good to me.

Acked-by: Juri Lelli <juri.lelli@arm.com>

Thanks,

- Juri