[PATCH review for 4.9 15/50] sched/fair: Update rq clock before changing a task's CPU affinity

[Levin, Alexander (Sasha Levin)]

From: Wanpeng Li <wanpeng.li@xxxxxxxxxxx>

[ Upstream commit a499c3ead88ccf147fc50689e85a530ad923ce36 ]

This is triggered during boot when CONFIG_SCHED_DEBUG is enabled:

 ------------[ cut here ]------------
 WARNING: CPU: 6 PID: 81 at kernel/sched/sched.h:812 set_next_entity+0x11d/0x380
 rq->clock_update_flags < RQCF_ACT_SKIP
 CPU: 6 PID: 81 Comm: torture_shuffle Not tainted 4.10.0+ #1
 Hardware name: LENOVO ThinkCentre M8500t-N000/SHARKBAY, BIOS FBKTC1AUS 02/16/2016
 Call Trace:
  dump_stack+0x85/0xc2
  __warn+0xcb/0xf0
  warn_slowpath_fmt+0x5f/0x80
  set_next_entity+0x11d/0x380
  set_curr_task_fair+0x2b/0x60
  do_set_cpus_allowed+0x139/0x180
  __set_cpus_allowed_ptr+0x113/0x260
  set_cpus_allowed_ptr+0x10/0x20
  torture_shuffle+0xfd/0x180
  kthread+0x10f/0x150
  ? torture_shutdown_init+0x60/0x60
  ? kthread_create_on_node+0x60/0x60
  ret_from_fork+0x31/0x40
 ---[ end trace dd94d92344cea9c6 ]---

The task is running && !queued, so there is no rq clock update before calling
set_curr_task().

This patch fixes it by updating rq clock after holding rq->lock/pi_lock
just as what other dequeue + put_prev + enqueue + set_curr story does.

Signed-off-by: Wanpeng Li <wanpeng.li@xxxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Reviewed-by: Matt Fleming <matt@xxxxxxxxxxxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Mike Galbraith <efault@xxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/1487749975-5994-1-git-send-email-wanpeng.li@xxxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxx>
---
 kernel/sched/core.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 2098954c690f..d271a1c387eb 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1141,6 +1141,7 @@ static int __set_cpus_allowed_ptr(struct task_struct *p,
 	int ret = 0;
 
 	rq = task_rq_lock(p, &rf);
+	update_rq_clock(rq);
 
 	if (p->flags & PF_KTHREAD) {
 		/*
-- 
2.11.0