alinux: sched: Fix %steal in cpuacct.proc_stat in guest OS

to #28143829

rq_clock_task is less than rq_clock when in VM, or when IRQ_TIME_ACCOUNTING
is on. So they are not comparable when accounting elapsed time. This bug is
not observed on host yet, because neither of these two conditions are met.

Use rq_clock at both begin and end of exec_start_raw accumulation to fix
this bug, because we expect steal% in cpuacct.proc_stat of VM's cgroups can
reflect the cpu time the host steal from the guest.

Fixes: c7552980 ("alinux: sched: Introduce per-cgroup steal accounting")
Signed-off-by: NYihao Wu <wuyihao@linux.alibaba.com>
Acked-by: NMichael Wang <yun.wang@linux.alibaba.com>

kernel/sched/fair.c

@@ -1023,7 +1023,7 @@ update_stats_curr_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
 	 * We are starting a new run period:
 	 */
 	se->exec_start = rq_clock_task(rq_of(cfs_rq));
-	se->exec_start_raw = rq_clock_task(rq_of(cfs_rq));
+	se->exec_start_raw = rq_clock(rq_of(cfs_rq));
 }
 
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