linux-kernel - [PATCH AUTOSEL for 4.9 048/156] sched/deadline: Add missing update_rq_clock() in dl_task

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Date:   Thu, 7 Dec 2017 15:49:06 +0000
From:   alexander.levin@...izon.com
To:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
Cc:     Wanpeng Li <wanpeng.li@...mail.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Juri Lelli <juri.lelli@....com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Mike Galbraith <efault@....de>,
        "Thomas Gleixner" <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>, alexander.levin@...izon.com
Subject: [PATCH AUTOSEL for 4.9 048/156] sched/deadline: Add missing
 update_rq_clock() in dl_task_timer()

From: Wanpeng Li <wanpeng.li@...mail.com>

[ Upstream commit dcc3b5ffe1b32771c9a22e2c916fb94c4fcf5b79 ]

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.

Signed-off-by: Wanpeng Li <wanpeng.li@...mail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Reviewed-by: Matt Fleming <matt@...eblueprint.co.uk>
Cc: Juri Lelli <juri.lelli@....com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Mike Galbraith <efault@....de>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Link: http://lkml.kernel.org/r/1488865888-15894-1-git-send-email-wanpeng.li@hotmail.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Signed-off-by: Sasha Levin <alexander.levin@...izon.com>
---
 kernel/sched/deadline.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index c95c5122b105..b0598b2bad88 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);
 
 		/*
 		 * Now that the task has been migrated to the new RQ and we
-- 
2.11.0