[PATCH v2] cgroup: use a per-cgroup work for release agent
From: Zefan Li
Date: Thu Sep 18 2014 - 04:06:44 EST
Instead of using a global work to schedule release agent on removable
cgroups, we change to use a per-cgroup work to do this, which makes
the code much simpler.
v2: use a dedicated work instead of reusing css->destroy_work. (Tejun)
Signed-off-by: Zefan Li <lizefan@xxxxxxxxxx>
---
include/linux/cgroup.h | 10 ++---
kernel/cgroup.c | 108 +++++++++++++++----------------------------------
2 files changed, 36 insertions(+), 82 deletions(-)
diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index a5d9b8f..77a1d37 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -235,13 +235,6 @@ struct cgroup {
struct list_head e_csets[CGROUP_SUBSYS_COUNT];
/*
- * Linked list running through all cgroups that can
- * potentially be reaped by the release agent. Protected by
- * release_list_lock
- */
- struct list_head release_list;
-
- /*
* list of pidlists, up to two for each namespace (one for procs, one
* for tasks); created on demand.
*/
@@ -250,6 +243,9 @@ struct cgroup {
/* used to wait for offlining of csses */
wait_queue_head_t offline_waitq;
+
+ /* used to schedule release agent */
+ struct work_struct release_agent_work;
};
#define MAX_CGROUP_ROOT_NAMELEN 64
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index e91bc3c..2332efd 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -392,12 +392,7 @@ static int notify_on_release(const struct cgroup *cgrp)
; \
else
-/* the list of cgroups eligible for automatic release. Protected by
- * release_list_lock */
-static LIST_HEAD(release_list);
-static DEFINE_RAW_SPINLOCK(release_list_lock);
static void cgroup_release_agent(struct work_struct *work);
-static DECLARE_WORK(release_agent_work, cgroup_release_agent);
static void check_for_release(struct cgroup *cgrp);
/*
@@ -1577,7 +1572,6 @@ static void init_cgroup_housekeeping(struct cgroup *cgrp)
INIT_LIST_HEAD(&cgrp->self.sibling);
INIT_LIST_HEAD(&cgrp->self.children);
INIT_LIST_HEAD(&cgrp->cset_links);
- INIT_LIST_HEAD(&cgrp->release_list);
INIT_LIST_HEAD(&cgrp->pidlists);
mutex_init(&cgrp->pidlist_mutex);
cgrp->self.cgroup = cgrp;
@@ -1587,6 +1581,7 @@ static void init_cgroup_housekeeping(struct cgroup *cgrp)
INIT_LIST_HEAD(&cgrp->e_csets[ssid]);
init_waitqueue_head(&cgrp->offline_waitq);
+ INIT_WORK(&cgrp->release_agent_work, cgroup_release_agent);
}
static void init_cgroup_root(struct cgroup_root *root,
@@ -4342,6 +4337,7 @@ static void css_free_work_fn(struct work_struct *work)
/* cgroup free path */
atomic_dec(&cgrp->root->nr_cgrps);
cgroup_pidlist_destroy_all(cgrp);
+ cancel_work_sync(&cgrp->release_agent_work);
if (cgroup_parent(cgrp)) {
/*
@@ -4804,12 +4800,6 @@ static int cgroup_destroy_locked(struct cgroup *cgrp)
for_each_css(css, ssid, cgrp)
kill_css(css);
- /* CSS_ONLINE is clear, remove from ->release_list for the last time */
- raw_spin_lock(&release_list_lock);
- if (!list_empty(&cgrp->release_list))
- list_del_init(&cgrp->release_list);
- raw_spin_unlock(&release_list_lock);
-
/*
* Remove @cgrp directory along with the base files. @cgrp has an
* extra ref on its kn.
@@ -5259,25 +5249,9 @@ void cgroup_exit(struct task_struct *tsk)
static void check_for_release(struct cgroup *cgrp)
{
- if (cgroup_is_releasable(cgrp) && list_empty(&cgrp->cset_links) &&
- !css_has_online_children(&cgrp->self)) {
- /*
- * Control Group is currently removeable. If it's not
- * already queued for a userspace notification, queue
- * it now
- */
- int need_schedule_work = 0;
-
- raw_spin_lock(&release_list_lock);
- if (!cgroup_is_dead(cgrp) &&
- list_empty(&cgrp->release_list)) {
- list_add(&cgrp->release_list, &release_list);
- need_schedule_work = 1;
- }
- raw_spin_unlock(&release_list_lock);
- if (need_schedule_work)
- schedule_work(&release_agent_work);
- }
+ if (cgroup_is_releasable(cgrp) && !cgroup_has_tasks(cgrp) &&
+ !css_has_online_children(&cgrp->self) && !cgroup_is_dead(cgrp))
+ schedule_work(&cgrp->release_agent_work);
}
/*
@@ -5305,52 +5279,36 @@ static void check_for_release(struct cgroup *cgrp)
*/
static void cgroup_release_agent(struct work_struct *work)
{
- BUG_ON(work != &release_agent_work);
+ struct cgroup *cgrp =
+ container_of(work, struct cgroup, release_agent_work);
+ char *pathbuf = NULL, *agentbuf = NULL, *path;
+ char *argv[3], *envp[3];
+
mutex_lock(&cgroup_mutex);
- raw_spin_lock(&release_list_lock);
- while (!list_empty(&release_list)) {
- char *argv[3], *envp[3];
- int i;
- char *pathbuf = NULL, *agentbuf = NULL, *path;
- struct cgroup *cgrp = list_entry(release_list.next,
- struct cgroup,
- release_list);
- list_del_init(&cgrp->release_list);
- raw_spin_unlock(&release_list_lock);
- pathbuf = kmalloc(PATH_MAX, GFP_KERNEL);
- if (!pathbuf)
- goto continue_free;
- path = cgroup_path(cgrp, pathbuf, PATH_MAX);
- if (!path)
- goto continue_free;
- agentbuf = kstrdup(cgrp->root->release_agent_path, GFP_KERNEL);
- if (!agentbuf)
- goto continue_free;
-
- i = 0;
- argv[i++] = agentbuf;
- argv[i++] = path;
- argv[i] = NULL;
-
- i = 0;
- /* minimal command environment */
- envp[i++] = "HOME=/";
- envp[i++] = "PATH=/sbin:/bin:/usr/sbin:/usr/bin";
- envp[i] = NULL;
-
- /* Drop the lock while we invoke the usermode helper,
- * since the exec could involve hitting disk and hence
- * be a slow process */
- mutex_unlock(&cgroup_mutex);
- call_usermodehelper(argv[0], argv, envp, UMH_WAIT_EXEC);
- mutex_lock(&cgroup_mutex);
- continue_free:
- kfree(pathbuf);
- kfree(agentbuf);
- raw_spin_lock(&release_list_lock);
- }
- raw_spin_unlock(&release_list_lock);
+
+ pathbuf = kmalloc(PATH_MAX, GFP_KERNEL);
+ agentbuf = kstrdup(cgrp->root->release_agent_path, GFP_KERNEL);
+ if (!pathbuf || !agentbuf)
+ goto out;
+
+ path = cgroup_path(cgrp, pathbuf, PATH_MAX);
+ if (!path)
+ goto out;
+
+ argv[0] = agentbuf;
+ argv[1] = path;
+ argv[2] = NULL;
+
+ /* minimal command environment */
+ envp[0] = "HOME=/";
+ envp[1] = "PATH=/sbin:/bin:/usr/sbin:/usr/bin";
+ envp[2] = NULL;
+
mutex_unlock(&cgroup_mutex);
+ call_usermodehelper(argv[0], argv, envp, UMH_WAIT_EXEC);
+out:
+ kfree(agentbuf);
+ kfree(pathbuf);
}
static int __init cgroup_disable(char *str)
--
1.8.0.2
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