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

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@redhat.com>
Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Signed-off-by: Juri Lelli <juri.lelli@redhat.com>
Reviewed-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Qais Yousef (Google) <qyousef@layalina.io>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/include/linux/sched.h b/include/linux/sched.h
index b2e30fbbeef051a33d58581ab6119d2d1191f955..0cac69902ec5806ff7765fa80199bde668c8d35a 100644 (file)
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1846,7 +1846,7 @@ current_restore_flags(unsigned long orig_flags, unsigned long flags)
 }
 
 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

diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index eca07ff716563a2793c17b75dc0a0c3d808fed3c..db3e05b6b4dd2f0582f386730e5ec1a4f401c9bc 100644 (file)
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -198,6 +198,8 @@ 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;
 
        /* Invalid partition error code, not lock protected */
        enum prs_errcode prs_err;
@@ -2491,16 +2493,23 @@ static int cpuset_can_attach_check(struct cpuset *cs)
        return 0;
 }
 
+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);
@@ -2511,7 +2520,7 @@ static int cpuset_can_attach(struct cgroup_taskset *tset)
                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);
@@ -2519,11 +2528,31 @@ static int cpuset_can_attach(struct cgroup_taskset *tset)
                        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.
@@ -2546,6 +2575,14 @@ static void cpuset_cancel_attach(struct cgroup_taskset *tset)
        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);
 }
 
@@ -2623,6 +2660,12 @@ static void cpuset_attach(struct cgroup_taskset *tset)
 
        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);
@@ -3298,7 +3341,7 @@ static int cpuset_can_fork(struct task_struct *task, struct css_set *cset)
        if (ret)
                goto out_unlock;
 
-       ret = task_can_attach(task, cs->effective_cpus);
+       ret = task_can_attach(task);
        if (ret)
                goto out_unlock;
 

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 6963fc4ef8976bdb2e1e202d92e359266722ac63..0f6a92737c91230aa1ebe54c868005db5682ea82 100644 (file)
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -9083,8 +9083,7 @@ int cpuset_cpumask_can_shrink(const struct cpumask *cur,
        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;
 
@@ -9097,21 +9096,9 @@ int task_can_attach(struct task_struct *p,
         * 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;
 }