[PATCH v2 1/3] sched/fair: Remove the write-order dependency between cpu.max and cpu.max.burst

[Zhe Liu <liuzhe1@kylinos.cn>]

Keep the configured burst independent of the current quota and cap it
when CFS refills runtime. This allows quota and burst updates in either
order.

Fixes: f4183717b370 ("sched/fair: Introduce the burstable CFS controller")

Cc: stable@vger.kernel.org
Signed-off-by: Zhe Liu <liuzhe1@kylinos.cn>
---
 kernel/sched/core.c | 3 +--
 kernel/sched/fair.c | 3 ++-
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index f78275192036..5269b8cfcf7f 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -10159,8 +10159,7 @@ static int tg_set_bandwidth(struct task_group *tg,
 	if (quota_us != RUNTIME_INF && quota_us > max_bw_runtime_us)
 		return -EINVAL;
 
-	if (quota_us != RUNTIME_INF && (burst_us > quota_us ||
-					burst_us + quota_us > max_bw_runtime_us))
+	if (burst_us > max_bw_runtime_us)
 		return -EINVAL;
 
 #ifdef CONFIG_CFS_BANDWIDTH
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 6d881e530f89..488de18d477e 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -6627,7 +6627,8 @@ void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth *cfs_b)
 		cfs_b->nr_burst++;
 	}
 
-	cfs_b->runtime = min(cfs_b->runtime, cfs_b->quota + cfs_b->burst);
+	cfs_b->runtime = min(cfs_b->runtime,
+			     cfs_b->quota + min(cfs_b->burst, cfs_b->quota));
 	cfs_b->runtime_snap = cfs_b->runtime;
 }
 
-- 
2.25.1