[PATCH RT 4/2] hrtimer: Don't lose state in cpu_chill()

[Sebastian Andrzej Siewior]

In cpu_chill() the state is set to TASK_UNINTERRUPTIBLE and a timer is
programmed. On return the state is always TASK_RUNNING which means we
lose the state if it was something other than RUNNING. Also
set_current_state() sets ->task_state_change to within cpu_chill() which
is not expected.

Save the task state on entry and restore it on return. Simply set the
state in order to avoid updating ->task_state_change.

Cc: stable-rt@xxxxxxxxxxxxxxx
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
---
 kernel/time/hrtimer.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/kernel/time/hrtimer.c b/kernel/time/hrtimer.c
index 851b2134e77f4..6f2736ec4b8ef 100644
--- a/kernel/time/hrtimer.c
+++ b/kernel/time/hrtimer.c
@@ -1902,15 +1902,18 @@ void cpu_chill(void)
 {
 	ktime_t chill_time;
 	unsigned int freeze_flag = current->flags & PF_NOFREEZE;
+	long saved_state;
 
+	saved_state = current->state;
 	chill_time = ktime_set(0, NSEC_PER_MSEC);
-	set_current_state(TASK_UNINTERRUPTIBLE);
+	__set_current_state_no_track(TASK_UNINTERRUPTIBLE);
 	current->flags |= PF_NOFREEZE;
 	sleeping_lock_inc();
 	schedule_hrtimeout(&chill_time, HRTIMER_MODE_REL_HARD);
 	sleeping_lock_dec();
 	if (!freeze_flag)
 		current->flags &= ~PF_NOFREEZE;
+	__set_current_state_no_track(saved_state);
 }
 EXPORT_SYMBOL(cpu_chill);
 #endif
-- 
2.20.1