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Date: Sun, 9 Jun 2013 17:14:47 +0800
From: Li Zefan <lizefan@...wei.com>
To: Tejun Heo <tj@...nel.org>
CC: Cgroups <cgroups@...r.kernel.org>,
LKML <linux-kernel@...r.kernel.org>,
Containers <containers@...ts.linux-foundation.org>
Subject: [PATCH v3 2/7] cpuset: remove async hotplug propagation work
As we can drop rcu read lock while iterating cgroup hierarchy,
we don't have to do propagation asynchronously via workqueue.
Signed-off-by: Li Zefan <lizefan@...wei.com>
---
kernel/cpuset.c | 69 +++++++++++++--------------------------------------------
1 file changed, 16 insertions(+), 53 deletions(-)
diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index 5ffcc3b..2d68d5c 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -101,8 +101,6 @@ struct cpuset {
/* for custom sched domain */
int relax_domain_level;
-
- struct work_struct hotplug_work;
};
/* Retrieve the cpuset for a cgroup */
@@ -268,12 +266,7 @@ static DEFINE_MUTEX(callback_mutex);
/*
* CPU / memory hotplug is handled asynchronously.
*/
-static struct workqueue_struct *cpuset_propagate_hotplug_wq;
-
static void cpuset_hotplug_workfn(struct work_struct *work);
-static void cpuset_propagate_hotplug_workfn(struct work_struct *work);
-static void schedule_cpuset_propagate_hotplug(struct cpuset *cs);
-
static DECLARE_WORK(cpuset_hotplug_work, cpuset_hotplug_workfn);
static DECLARE_WAIT_QUEUE_HEAD(cpuset_attach_wq);
@@ -1554,7 +1547,6 @@ static int cpuset_write_resmask(struct cgroup *cgrp, struct cftype *cft,
* after execution capability is restored.
*/
flush_work(&cpuset_hotplug_work);
- flush_workqueue(cpuset_propagate_hotplug_wq);
mutex_lock(&cpuset_mutex);
if (!is_cpuset_online(cs))
@@ -1821,7 +1813,6 @@ static struct cgroup_subsys_state *cpuset_css_alloc(struct cgroup *cont)
cpumask_clear(cs->cpus_allowed);
nodes_clear(cs->mems_allowed);
fmeter_init(&cs->fmeter);
- INIT_WORK(&cs->hotplug_work, cpuset_propagate_hotplug_workfn);
cs->relax_domain_level = -1;
return &cs->css;
@@ -1984,18 +1975,17 @@ static void remove_tasks_in_empty_cpuset(struct cpuset *cs)
}
/**
- * cpuset_propagate_hotplug_workfn - propagate CPU/memory hotplug to a cpuset
+ * cpuset_hotplug_update_tasks - update tasks in a cpuset for hotunplug
* @cs: cpuset in interest
*
* Compare @cs's cpu and mem masks against top_cpuset and if some have gone
* offline, update @cs accordingly. If @cs ends up with no CPU or memory,
* all its tasks are moved to the nearest ancestor with both resources.
*/
-static void cpuset_propagate_hotplug_workfn(struct work_struct *work)
+static void cpuset_hotplug_update_tasks(struct cpuset *cs)
{
static cpumask_t off_cpus;
static nodemask_t off_mems, tmp_mems;
- struct cpuset *cs = container_of(work, struct cpuset, hotplug_work);
bool is_empty;
retry:
@@ -2044,34 +2034,6 @@ retry:
*/
if (is_empty)
remove_tasks_in_empty_cpuset(cs);
-
- /* the following may free @cs, should be the last operation */
- css_put(&cs->css);
-}
-
-/**
- * schedule_cpuset_propagate_hotplug - schedule hotplug propagation to a cpuset
- * @cs: cpuset of interest
- *
- * Schedule cpuset_propagate_hotplug_workfn() which will update CPU and
- * memory masks according to top_cpuset.
- */
-static void schedule_cpuset_propagate_hotplug(struct cpuset *cs)
-{
- /*
- * Pin @cs. The refcnt will be released when the work item
- * finishes executing.
- */
- if (!css_tryget(&cs->css))
- return;
-
- /*
- * Queue @cs->hotplug_work. If already pending, lose the css ref.
- * cpuset_propagate_hotplug_wq is ordered and propagation will
- * happen in the order this function is called.
- */
- if (!queue_work(cpuset_propagate_hotplug_wq, &cs->hotplug_work))
- css_put(&cs->css);
}
/**
@@ -2084,8 +2046,8 @@ static void schedule_cpuset_propagate_hotplug(struct cpuset *cs)
* actively using CPU hotplug but making no active use of cpusets.
*
* Non-root cpusets are only affected by offlining. If any CPUs or memory
- * nodes have been taken down, cpuset_propagate_hotplug() is invoked on all
- * descendants.
+ * nodes have been taken down, cpuset_hotplug_update_tasks() is invoked on
+ * all descendants.
*
* Note that CPU offlining during suspend is ignored. We don't modify
* cpusets across suspend/resume cycles at all.
@@ -2128,21 +2090,26 @@ static void cpuset_hotplug_workfn(struct work_struct *work)
update_tasks_nodemask(&top_cpuset, &tmp_mems, NULL);
}
+ mutex_unlock(&cpuset_mutex);
+
/* if cpus or mems went down, we need to propagate to descendants */
if (cpus_offlined || mems_offlined) {
struct cpuset *cs;
struct cgroup *pos_cgrp;
rcu_read_lock();
- cpuset_for_each_descendant_pre(cs, pos_cgrp, &top_cpuset)
- schedule_cpuset_propagate_hotplug(cs);
- rcu_read_unlock();
- }
+ cpuset_for_each_descendant_pre(cs, pos_cgrp, &top_cpuset) {
+ if (!css_tryget(&cs->css))
+ continue;
+ rcu_read_unlock();
- mutex_unlock(&cpuset_mutex);
+ cpuset_hotplug_update_tasks(cs);
- /* wait for propagations to finish */
- flush_workqueue(cpuset_propagate_hotplug_wq);
+ rcu_read_lock();
+ css_put(&cs->css);
+ }
+ rcu_read_unlock();
+ }
/* rebuild sched domains if cpus_allowed has changed */
if (cpus_updated)
@@ -2193,10 +2160,6 @@ void __init cpuset_init_smp(void)
top_cpuset.mems_allowed = node_states[N_MEMORY];
register_hotmemory_notifier(&cpuset_track_online_nodes_nb);
-
- cpuset_propagate_hotplug_wq =
- alloc_ordered_workqueue("cpuset_hotplug", 0);
- BUG_ON(!cpuset_propagate_hotplug_wq);
}
/**
--
1.8.0.2
--
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