Patch "sched/fair: Update rq clock before changing a task's CPU affinity" has been added to the 4.9-stable tree

This is a note to let you know that I've just added the patch titled

sched/fair: Update rq clock before changing a task's CPU affinity

to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
sched-fair-update-rq-clock-before-changing-a-task-s-cpu-affinity.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Wanpeng Li <[email protected]>
Date: Tue, 21 Feb 2017 23:52:55 -0800
Subject: sched/fair: Update rq clock before changing a task's CPU affinity

From: Wanpeng Li <[email protected]>

[ 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.

---
 kernel/sched/core.c |    1 +
 1 file changed, 1 insertion(+)

@@ -1141,6 +1141,7 @@ static int __set_cpus_allowed_ptr(struct
 	int ret = 0;
 
 	rq = task_rq_lock(p, &rf);
+	update_rq_clock(rq);
 
 	if (p->flags & PF_KTHREAD) {
 		/*

Patches currently in stable-queue which might be from [email protected] are

queue-4.9/sched-fair-update-rq-clock-before-changing-a-task-s-cpu-affinity.patch