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@@ -89,6 +89,14 @@ static DEFINE_MUTEX(cgroup_mutex);
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static DEFINE_MUTEX(cgroup_root_mutex);
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+/*
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+ * cgroup destruction makes heavy use of work items and there can be a lot
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+ * of concurrent destructions. Use a separate workqueue so that cgroup
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+ * destruction work items don't end up filling up max_active of system_wq
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+ * which may lead to deadlock.
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+ */
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+static struct workqueue_struct *cgroup_destroy_wq;
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+
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/*
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* Generate an array of cgroup subsystem pointers. At boot time, this is
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* populated with the built in subsystems, and modular subsystems are
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@@ -871,7 +879,7 @@ static void cgroup_free_rcu(struct rcu_head *head)
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struct cgroup *cgrp = container_of(head, struct cgroup, rcu_head);
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INIT_WORK(&cgrp->destroy_work, cgroup_free_fn);
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- schedule_work(&cgrp->destroy_work);
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+ queue_work(cgroup_destroy_wq, &cgrp->destroy_work);
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}
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static void cgroup_diput(struct dentry *dentry, struct inode *inode)
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@@ -4249,7 +4257,7 @@ static void css_free_rcu_fn(struct rcu_head *rcu_head)
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* css_put(). dput() requires process context which we don't have.
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*/
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INIT_WORK(&css->destroy_work, css_free_work_fn);
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- schedule_work(&css->destroy_work);
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+ queue_work(cgroup_destroy_wq, &css->destroy_work);
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}
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static void css_release(struct percpu_ref *ref)
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@@ -4539,7 +4547,7 @@ static void css_killed_ref_fn(struct percpu_ref *ref)
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container_of(ref, struct cgroup_subsys_state, refcnt);
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INIT_WORK(&css->destroy_work, css_killed_work_fn);
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- schedule_work(&css->destroy_work);
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+ queue_work(cgroup_destroy_wq, &css->destroy_work);
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}
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/**
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@@ -5063,6 +5071,22 @@ out:
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return err;
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}
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+static int __init cgroup_wq_init(void)
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+{
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+ /*
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+ * There isn't much point in executing destruction path in
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+ * parallel. Good chunk is serialized with cgroup_mutex anyway.
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+ * Use 1 for @max_active.
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+ *
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+ * We would prefer to do this in cgroup_init() above, but that
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+ * is called before init_workqueues(): so leave this until after.
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+ */
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+ cgroup_destroy_wq = alloc_workqueue("cgroup_destroy", 0, 1);
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+ BUG_ON(!cgroup_destroy_wq);
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+ return 0;
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+}
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+core_initcall(cgroup_wq_init);
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+
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/*
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* proc_cgroup_show()
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* - Print task's cgroup paths into seq_file, one line for each hierarchy
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