linux-kernel - [PATCH 12/39] sched: Add normal

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Date: Wed,  1 May 2024 05:09:47 -1000
From: Tejun Heo <tj@...nel.org>
To: torvalds@...ux-foundation.org,
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Cc: linux-kernel@...r.kernel.org,
	bpf@...r.kernel.org,
	kernel-team@...a.com,
	Tejun Heo <tj@...nel.org>
Subject: [PATCH 12/39] sched: Add normal_policy()

A new BPF extensible sched_class will need to dynamically change how a task
picks its sched_class. For example, if the loaded BPF scheduler progs fail,
the tasks will be forced back on CFS even if the task's policy is set to the
new sched_class. To support such mapping, add normal_policy() which wraps
testing for %SCHED_NORMAL. This doesn't cause any behavior changes.

v2: Update the description with more details on the expected use.

Signed-off-by: Tejun Heo <tj@...nel.org>
Reviewed-by: David Vernet <dvernet@...a.com>
Acked-by: Josh Don <joshdon@...gle.com>
Acked-by: Hao Luo <haoluo@...gle.com>
Acked-by: Barret Rhoden <brho@...gle.com>
---
 kernel/sched/fair.c  | 2 +-
 kernel/sched/sched.h | 8 +++++++-
 2 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 51301ae13725..8a9b2e95d06b 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -8322,7 +8322,7 @@ static void check_preempt_wakeup_fair(struct rq *rq, struct task_struct *p, int
 	 * Batch and idle tasks do not preempt non-idle tasks (their preemption
 	 * is driven by the tick):
 	 */
-	if (unlikely(p->policy != SCHED_NORMAL) || !sched_feat(WAKEUP_PREEMPTION))
+	if (unlikely(!normal_policy(p->policy)) || !sched_feat(WAKEUP_PREEMPTION))
 		return;
 
 	find_matching_se(&se, &pse);
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index ccf2fff0e2ae..11b4345d2638 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -171,9 +171,15 @@ static inline int idle_policy(int policy)
 {
 	return policy == SCHED_IDLE;
 }
+
+static inline int normal_policy(int policy)
+{
+	return policy == SCHED_NORMAL;
+}
+
 static inline int fair_policy(int policy)
 {
-	return policy == SCHED_NORMAL || policy == SCHED_BATCH;
+	return normal_policy(policy) || policy == SCHED_BATCH;
 }
 
 static inline int rt_policy(int policy)
-- 
2.44.0