The comments above dl_get_task_effective_cpus() and
dl_add_task_root_domain() already explain how to fetch a valid
root domain and protect against races. There's no need to repeat
this inside dl_add_task_root_domain(). Remove the redundant comment
to keep the code clean.

No functional change.

Signed-off-by: Pingfan Liu <piliu@redhat.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Waiman Long <longman@redhat.com>
Cc: Chen Ridong <chenridong@huaweicloud.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Pierre Gondois <pierre.gondois@arm.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Ben Segall <bsegall@google.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Valentin Schneider <vschneid@redhat.com>
To: cgroups@vger.kernel.org
To: linux-kernel@vger.kernel.org
---
 kernel/sched/deadline.c | 9 ---------
 1 file changed, 9 deletions(-)

diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index 194a341e85864..0b6646259bcd7 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -2952,20 +2952,11 @@ void dl_add_task_root_domain(struct task_struct *p)
 		return;
 	}
 
-	/*
-	 * Get an active rq, whose rq->rd traces the correct root
-	 * domain.
-	 * Ideally this would be under cpuset reader lock until rq->rd is
-	 * fetched.  However, sleepable locks cannot nest inside pi_lock, so we
-	 * rely on the caller of dl_add_task_root_domain() holds 'cpuset_mutex'
-	 * to guarantee the CPU stays in the cpuset.
-	 */
 	dl_get_task_effective_cpus(p, msk);
 	cpu = cpumask_first_and(cpu_active_mask, msk);
 	BUG_ON(cpu >= nr_cpu_ids);
 	rq = cpu_rq(cpu);
 	dl_b = &rq->rd->dl_bw;
-	/* End of fetching rd */
 
 	raw_spin_lock(&dl_b->lock);
 	__dl_add(dl_b, p->dl.dl_bw, cpumask_weight(rq->rd->span));
-- 
2.49.0

The following commit has been merged into the sched/urgent branch of tip:

Commit-ID:     479972efc2e7c9e0b3743ac538b042fcd4f315d7
Gitweb:        https://git.kernel.org/tip/479972efc2e7c9e0b3743ac538b042fcd4f315d7
Author:        Pingfan Liu <piliu@redhat.com>
AuthorDate:    Tue, 25 Nov 2025 11:26:29 +08:00
Committer:     Peter Zijlstra <peterz@infradead.org>
CommitterDate: Tue, 13 Jan 2026 11:37:51 +01:00

sched/deadline: Remove unnecessary comment in dl_add_task_root_domain()

The comments above dl_get_task_effective_cpus() and
dl_add_task_root_domain() already explain how to fetch a valid
root domain and protect against races. There's no need to repeat
this inside dl_add_task_root_domain(). Remove the redundant comment
to keep the code clean.

No functional change.

Signed-off-by: Pingfan Liu <piliu@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Juri Lelli <juri.lelli@redhat.com>
Acked-by: Waiman Long <longman@redhat.com>
Link: https://patch.msgid.link/20251125032630.8746-2-piliu@redhat.com
---
 kernel/sched/deadline.c |  9 ---------
 1 file changed, 9 deletions(-)

diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index 319439f..463ba50 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -3162,20 +3162,11 @@ void dl_add_task_root_domain(struct task_struct *p)
 		return;
 	}
 
-	/*
-	 * Get an active rq, whose rq->rd traces the correct root
-	 * domain.
-	 * Ideally this would be under cpuset reader lock until rq->rd is
-	 * fetched.  However, sleepable locks cannot nest inside pi_lock, so we
-	 * rely on the caller of dl_add_task_root_domain() holds 'cpuset_mutex'
-	 * to guarantee the CPU stays in the cpuset.
-	 */
 	dl_get_task_effective_cpus(p, msk);
 	cpu = cpumask_first_and(cpu_active_mask, msk);
 	BUG_ON(cpu >= nr_cpu_ids);
 	rq = cpu_rq(cpu);
 	dl_b = &rq->rd->dl_bw;
-	/* End of fetching rd */
 
 	raw_spin_lock(&dl_b->lock);
 	__dl_add(dl_b, p->dl.dl_bw, cpumask_weight(rq->rd->span));