[PATCH] fix share rt runtime with offline rq

[chenying]

In my environment,cpu0-11 are online, cpu12-15 are offline, CPU2 is isolated,
sched_rt_runtime_us is 950000,and then bind a rt process with dead loop to CPU2.
We can see that CPU usage on CPU2 reaches 100%,but only one cpu is isolated,
so it can be inferred that CPU2 shares the rt runtime of offline cpu.

/ # cat /sys/devices/system/cpu/online
0-11
/ # cat /sys/devices/system/cpu/offline
12-15
/ # cat /sys/devices/system/cpu/isolated
2
/ # cat /proc/sys/kernel/sched_rt_runtime_us
950000
/ # chrt -p 357
pid 357's current scheduling policy: SCHED_FIFO
pid 357's current scheduling priority: 1

top - 15:52:12 up 4 min,  0 users,  load average: 0.92, 0.41, 0.16
Tasks: 201 total,   2 running, 199 sleeping,   0 stopped,   0 zombie
%Cpu0  :  0.3 us,  0.3 sy,  0.0 ni, 99.3 id,  0.0 wa,  0.0 hi,  0.0 si,  0.0 st
%Cpu1  :  0.0 us,  0.0 sy,  0.0 ni,100.0 id,  0.0 wa,  0.0 hi,  0.0 si,  0.0 st
%Cpu2  :100.0 us,  0.0 sy,  0.0 ni,  0.0 id,  0.0 wa,  0.0 hi,  0.0 si,  0.0 st
%Cpu3  :  0.0 us,  0.0 sy,  0.0 ni,100.0 id,  0.0 wa,  0.0 hi,  0.0 si,  0.0 st
%Cpu4  :  0.0 us,  0.0 sy,  0.0 ni,100.0 id,  0.0 wa,  0.0 hi,  0.0 si,  0.0 st
%Cpu5  :  0.0 us,  0.0 sy,  0.0 ni,100.0 id,  0.0 wa,  0.0 hi,  0.0 si,  0.0 st
%Cpu6  :  0.0 us,  0.0 sy,  0.0 ni,100.0 id,  0.0 wa,  0.0 hi,  0.0 si,  0.0 st
%Cpu7  :  0.0 us,  0.0 sy,  0.0 ni,100.0 id,  0.0 wa,  0.0 hi,  0.0 si,  0.0 st
%Cpu8  :  0.0 us,  0.0 sy,  0.0 ni,100.0 id,  0.0 wa,  0.0 hi,  0.0 si,  0.0 st
%Cpu9  :  0.0 us,  0.0 sy,  0.0 ni,100.0 id,  0.0 wa,  0.0 hi,  0.0 si,  0.0 st
%Cpu10 :  0.0 us,  0.0 sy,  0.0 ni,100.0 id,  0.0 wa,  0.0 hi,  0.0 si,  0.0 st

  PID USER      PR  NI    VIRT    RES    SHR S  %CPU %MEM     TIME+ COMMAND
  357 root      -2   0    4044    172    136 R 100.0  0.0   2:32.99 deadloop
  366 root      20   0   22060   2404   2128 R   0.7  0.0   0:00.06 top
    1 root      20   0    2624     20      0 S   0.0  0.0   0:05.93 init
    2 root      20   0       0      0      0 S   0.0  0.0   0:00.00 kthreadd
    3 root      20   0       0      0      0 S   0.0  0.0   0:00.00 ksoftirqd/0
    4 root      20   0       0      0      0 S   0.0  0.0   0:00.00 kworker/0:0

Signed-off-by: chenying <chen.ying153@xxxxxxxxxx>
---
 kernel/sched/rt.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index a532558..d20dc86 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -648,8 +648,12 @@ static void do_balance_runtime(struct rt_rq *rt_rq)
 	rt_period = ktime_to_ns(rt_b->rt_period);
 	for_each_cpu(i, rd->span) {
 		struct rt_rq *iter = sched_rt_period_rt_rq(rt_b, i);
+		struct rq *rq = rq_of_rt_rq(iter);
 		s64 diff;
 
+		if (!rq->online)
+			continue;
+
 		if (iter == rt_rq)
 			continue;
 
-- 
2.15.2