Patch "cgroup/cpuset: Free DL BW in case can_attach() fails" has been added to the 5.15-stable tree

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This is a note to let you know that I've just added the patch titled

    cgroup/cpuset: Free DL BW in case can_attach() fails

to the 5.15-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     cgroup-cpuset-free-dl-bw-in-case-can_attach-fails.patch
and it can be found in the queue-5.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.


>From stable-owner@xxxxxxxxxxxxxxx Sun Aug 20 17:26:25 2023
From: Qais Yousef <qyousef@xxxxxxxxxxx>
Date: Sun, 20 Aug 2023 16:22:58 +0100
Subject: cgroup/cpuset: Free DL BW in case can_attach() fails
To: stable@xxxxxxxxxxxxxxx
Cc: Juri Lelli <juri.lelli@xxxxxxxxxx>, Waiman Long <longman@xxxxxxxxxx>, Tejun Heo <tj@xxxxxxxxxx>, Dietmar Eggemann <dietmar.eggemann@xxxxxxx>, Peter Zijlstra <peterz@xxxxxxxxxxxxx>, Vincent Guittot <vincent.guittot@xxxxxxxxxx>, Ingo Molnar <mingo@xxxxxxxxxx>, Hao Luo <haoluo@xxxxxxxxxx>, John Stultz <jstultz@xxxxxxxxxx>, cgroups@xxxxxxxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx, Qais Yousef <qyousef@xxxxxxxxxxx>
Message-ID: <20230820152258.518128-7-qyousef@xxxxxxxxxxx>

From: Dietmar Eggemann <dietmar.eggemann@xxxxxxx>

commit 2ef269ef1ac006acf974793d975539244d77b28f upstream.

cpuset_can_attach() can fail. Postpone DL BW allocation until all tasks
have been checked. DL BW is not allocated per-task but as a sum over
all DL tasks migrating.

If multiple controllers are attached to the cgroup next to the cpuset
controller a non-cpuset can_attach() can fail. In this case free DL BW
in cpuset_cancel_attach().

Finally, update cpuset DL task count (nr_deadline_tasks) only in
cpuset_attach().

Suggested-by: Waiman Long <longman@xxxxxxxxxx>
Signed-off-by: Dietmar Eggemann <dietmar.eggemann@xxxxxxx>
Signed-off-by: Juri Lelli <juri.lelli@xxxxxxxxxx>
Reviewed-by: Waiman Long <longman@xxxxxxxxxx>
Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
[ Conflict in kernel/cgroup/cpuset.c due to pulling extra neighboring
  functions that are not applicable on this branch. ]
Signed-off-by: Qais Yousef (Google) <qyousef@xxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 include/linux/sched.h  |    2 -
 kernel/cgroup/cpuset.c |   51 +++++++++++++++++++++++++++++++++++++++++++++----
 kernel/sched/core.c    |   17 +---------------
 3 files changed, 50 insertions(+), 20 deletions(-)

--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1797,7 +1797,7 @@ current_restore_flags(unsigned long orig
 }
 
 extern int cpuset_cpumask_can_shrink(const struct cpumask *cur, const struct cpumask *trial);
-extern int task_can_attach(struct task_struct *p, const struct cpumask *cs_effective_cpus);
+extern int task_can_attach(struct task_struct *p);
 extern int dl_bw_alloc(int cpu, u64 dl_bw);
 extern void dl_bw_free(int cpu, u64 dl_bw);
 #ifdef CONFIG_SMP
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -167,6 +167,8 @@ struct cpuset {
 	 * know when to rebuild associated root domain bandwidth information.
 	 */
 	int nr_deadline_tasks;
+	int nr_migrate_dl_tasks;
+	u64 sum_migrate_dl_bw;
 
 	/* Handle for cpuset.cpus.partition */
 	struct cgroup_file partition_file;
@@ -2206,16 +2208,23 @@ static int fmeter_getrate(struct fmeter
 
 static struct cpuset *cpuset_attach_old_cs;
 
+static void reset_migrate_dl_data(struct cpuset *cs)
+{
+	cs->nr_migrate_dl_tasks = 0;
+	cs->sum_migrate_dl_bw = 0;
+}
+
 /* Called by cgroups to determine if a cpuset is usable; cpuset_mutex held */
 static int cpuset_can_attach(struct cgroup_taskset *tset)
 {
 	struct cgroup_subsys_state *css;
-	struct cpuset *cs;
+	struct cpuset *cs, *oldcs;
 	struct task_struct *task;
 	int ret;
 
 	/* used later by cpuset_attach() */
 	cpuset_attach_old_cs = task_cs(cgroup_taskset_first(tset, &css));
+	oldcs = cpuset_attach_old_cs;
 	cs = css_cs(css);
 
 	mutex_lock(&cpuset_mutex);
@@ -2227,7 +2236,7 @@ static int cpuset_can_attach(struct cgro
 		goto out_unlock;
 
 	cgroup_taskset_for_each(task, css, tset) {
-		ret = task_can_attach(task, cs->effective_cpus);
+		ret = task_can_attach(task);
 		if (ret)
 			goto out_unlock;
 		ret = security_task_setscheduler(task);
@@ -2235,11 +2244,31 @@ static int cpuset_can_attach(struct cgro
 			goto out_unlock;
 
 		if (dl_task(task)) {
-			cs->nr_deadline_tasks++;
-			cpuset_attach_old_cs->nr_deadline_tasks--;
+			cs->nr_migrate_dl_tasks++;
+			cs->sum_migrate_dl_bw += task->dl.dl_bw;
 		}
 	}
 
+	if (!cs->nr_migrate_dl_tasks)
+		goto out_success;
+
+	if (!cpumask_intersects(oldcs->effective_cpus, cs->effective_cpus)) {
+		int cpu = cpumask_any_and(cpu_active_mask, cs->effective_cpus);
+
+		if (unlikely(cpu >= nr_cpu_ids)) {
+			reset_migrate_dl_data(cs);
+			ret = -EINVAL;
+			goto out_unlock;
+		}
+
+		ret = dl_bw_alloc(cpu, cs->sum_migrate_dl_bw);
+		if (ret) {
+			reset_migrate_dl_data(cs);
+			goto out_unlock;
+		}
+	}
+
+out_success:
 	/*
 	 * Mark attach is in progress.  This makes validate_change() fail
 	 * changes which zero cpus/mems_allowed.
@@ -2263,6 +2292,14 @@ static void cpuset_cancel_attach(struct
 	cs->attach_in_progress--;
 	if (!cs->attach_in_progress)
 		wake_up(&cpuset_attach_wq);
+
+	if (cs->nr_migrate_dl_tasks) {
+		int cpu = cpumask_any(cs->effective_cpus);
+
+		dl_bw_free(cpu, cs->sum_migrate_dl_bw);
+		reset_migrate_dl_data(cs);
+	}
+
 	mutex_unlock(&cpuset_mutex);
 }
 
@@ -2335,6 +2372,12 @@ static void cpuset_attach(struct cgroup_
 
 	cs->old_mems_allowed = cpuset_attach_nodemask_to;
 
+	if (cs->nr_migrate_dl_tasks) {
+		cs->nr_deadline_tasks += cs->nr_migrate_dl_tasks;
+		oldcs->nr_deadline_tasks -= cs->nr_migrate_dl_tasks;
+		reset_migrate_dl_data(cs);
+	}
+
 	cs->attach_in_progress--;
 	if (!cs->attach_in_progress)
 		wake_up(&cpuset_attach_wq);
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -8789,8 +8789,7 @@ int cpuset_cpumask_can_shrink(const stru
 	return ret;
 }
 
-int task_can_attach(struct task_struct *p,
-		    const struct cpumask *cs_effective_cpus)
+int task_can_attach(struct task_struct *p)
 {
 	int ret = 0;
 
@@ -8803,21 +8802,9 @@ int task_can_attach(struct task_struct *
 	 * success of set_cpus_allowed_ptr() on all attached tasks
 	 * before cpus_mask may be changed.
 	 */
-	if (p->flags & PF_NO_SETAFFINITY) {
+	if (p->flags & PF_NO_SETAFFINITY)
 		ret = -EINVAL;
-		goto out;
-	}
 
-	if (dl_task(p) && !cpumask_intersects(task_rq(p)->rd->span,
-					      cs_effective_cpus)) {
-		int cpu = cpumask_any_and(cpu_active_mask, cs_effective_cpus);
-
-		if (unlikely(cpu >= nr_cpu_ids))
-			return -EINVAL;
-		ret = dl_bw_alloc(cpu, p->dl.dl_bw);
-	}
-
-out:
 	return ret;
 }
 


Patches currently in stable-queue which might be from stable-owner@xxxxxxxxxxxxxxx are

queue-5.15/cgroup-cpuset-free-dl-bw-in-case-can_attach-fails.patch
queue-5.15/sched-cpuset-keep-track-of-sched_deadline-task-in-cpusets.patch
queue-5.15/cgroup-cpuset-rename-functions-dealing-with-deadline-accounting.patch
queue-5.15/cgroup-cpuset-iterate-only-if-deadline-tasks-are-present.patch
queue-5.15/sched-cpuset-bring-back-cpuset_mutex.patch
queue-5.15/sched-deadline-create-dl-bw-alloc-free-check-overflow-interface.patch



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