In order to reduce the critical section, we invoke sli_update_tick()
to do sli statistics after release the rq lock. But there is a race
condition that could led the rq_clock warning.
Warning generates like following:
CPU0 CPU1
rq_lock()
update_rq_clock()
rq_unlock()
rq_lock()
sli_update_tick() load balance
Although, CPU0 had updated the rq_clock(). But CPU1 may concurrently
do the load balance and acquire CPU0's rq lock, and the CPU0's
clock_update_flags would be cleared. It means that caller should
update the rq clock before actually use it. Unfortunately, CPU0
cann't observed it. So the warning was produced by sli when it
invoke rq_clock().
Therefore, we must move the sli_check_longsys() in the front of
rq_unlock().
Signed-off-by: Bin Lai <robinlai@tencent.com>
92e026f5b5