cpuset: let hotplug propagation work wait for task attaching
Instead of triggering propagation work in cpuset_attach(), we make hotplug propagation work wait until there's no task attaching in progress. IMO this is more robust. We won't see empty masks in cpuset_attach(). Also it's a preparation for removing propagation work. Without asynchronous propagation we can't call move_tasks_in_empty_cpuset() in cpuset_attach(), because otherwise we'll deadlock on cgroup_mutex. tj: typo fixes. Signed-off-by: Li Zefan <lizefan@huawei.com> Signed-off-by: Tejun Heo <tj@kernel.org>
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@ -59,6 +59,7 @@
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#include <linux/mutex.h>
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#include <linux/mutex.h>
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#include <linux/workqueue.h>
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#include <linux/workqueue.h>
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#include <linux/cgroup.h>
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#include <linux/cgroup.h>
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#include <linux/wait.h>
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/*
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/*
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* Tracks how many cpusets are currently defined in system.
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* Tracks how many cpusets are currently defined in system.
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@ -275,6 +276,8 @@ static void schedule_cpuset_propagate_hotplug(struct cpuset *cs);
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static DECLARE_WORK(cpuset_hotplug_work, cpuset_hotplug_workfn);
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static DECLARE_WORK(cpuset_hotplug_work, cpuset_hotplug_workfn);
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static DECLARE_WAIT_QUEUE_HEAD(cpuset_attach_wq);
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/*
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/*
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* This is ugly, but preserves the userspace API for existing cpuset
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* This is ugly, but preserves the userspace API for existing cpuset
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* users. If someone tries to mount the "cpuset" filesystem, we
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* users. If someone tries to mount the "cpuset" filesystem, we
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@ -1436,14 +1439,8 @@ static void cpuset_attach(struct cgroup *cgrp, struct cgroup_taskset *tset)
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}
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}
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cs->attach_in_progress--;
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cs->attach_in_progress--;
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if (!cs->attach_in_progress)
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/*
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wake_up(&cpuset_attach_wq);
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* We may have raced with CPU/memory hotunplug. Trigger hotplug
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* propagation if @cs doesn't have any CPU or memory. It will move
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* the newly added tasks to the nearest parent which can execute.
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*/
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if (cpumask_empty(cs->cpus_allowed) || nodes_empty(cs->mems_allowed))
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schedule_cpuset_propagate_hotplug(cs);
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mutex_unlock(&cpuset_mutex);
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mutex_unlock(&cpuset_mutex);
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}
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}
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@ -1555,10 +1552,6 @@ static int cpuset_write_resmask(struct cgroup *cgrp, struct cftype *cft,
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* resources, wait for the previously scheduled operations before
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* resources, wait for the previously scheduled operations before
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* proceeding, so that we don't end up keep removing tasks added
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* proceeding, so that we don't end up keep removing tasks added
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* after execution capability is restored.
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* after execution capability is restored.
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*
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* Flushing cpuset_hotplug_work is enough to synchronize against
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* hotplug hanlding; however, cpuset_attach() may schedule
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* propagation work directly. Flush the workqueue too.
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*/
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*/
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flush_work(&cpuset_hotplug_work);
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flush_work(&cpuset_hotplug_work);
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flush_workqueue(cpuset_propagate_hotplug_wq);
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flush_workqueue(cpuset_propagate_hotplug_wq);
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@ -2005,8 +1998,20 @@ static void cpuset_propagate_hotplug_workfn(struct work_struct *work)
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struct cpuset *cs = container_of(work, struct cpuset, hotplug_work);
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struct cpuset *cs = container_of(work, struct cpuset, hotplug_work);
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bool is_empty;
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bool is_empty;
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retry:
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wait_event(cpuset_attach_wq, cs->attach_in_progress == 0);
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mutex_lock(&cpuset_mutex);
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mutex_lock(&cpuset_mutex);
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/*
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* We have raced with task attaching. We wait until attaching
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* is finished, so we won't attach a task to an empty cpuset.
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*/
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if (cs->attach_in_progress) {
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mutex_unlock(&cpuset_mutex);
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goto retry;
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}
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cpumask_andnot(&off_cpus, cs->cpus_allowed, top_cpuset.cpus_allowed);
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cpumask_andnot(&off_cpus, cs->cpus_allowed, top_cpuset.cpus_allowed);
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nodes_andnot(off_mems, cs->mems_allowed, top_cpuset.mems_allowed);
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nodes_andnot(off_mems, cs->mems_allowed, top_cpuset.mems_allowed);
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