[PATCH 01/10] cgroup: introduce cgroup_[un]lock()

From: Tejun Heo
Date: Fri Mar 11 2016 - 10:46:24 EST

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Introduce thin wrappers which lock and unlock cgroup_mutex. While
this doesn't introduce any functional differences now, they will later
be used to perform some extra operations around locking.

Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
---
kernel/cgroup.c | 100 +++++++++++++++++++++++++++++++++-----------------------
1 file changed, 59 insertions(+), 41 deletions(-)

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index e22df5d8..2297bf6 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -237,6 +237,24 @@ static int cgroup_addrm_files(struct cgroup_subsys_state *css,
bool is_add);

/**
+ * cgroup_lock - lock cgroup_mutex and perform related operations
+ */
+static void cgroup_lock(void)
+ __acquires(&cgroup_mutex)
+{
+ mutex_lock(&cgroup_mutex);
+}
+
+/**
+ * cgroup_unlock - unlock cgroup_mutex and perform related operations
+ */
+static void cgroup_unlock(void)
+ __releases(&cgroup_mutex)
+{
+ mutex_unlock(&cgroup_mutex);
+}
+
+/**
* cgroup_ssid_enabled - cgroup subsys enabled test by subsys ID
* @ssid: subsys ID of interest
*
@@ -1194,7 +1212,7 @@ static void cgroup_destroy_root(struct cgroup_root *root)

cgroup_exit_root_id(root);

- mutex_unlock(&cgroup_mutex);
+ cgroup_unlock();

kernfs_destroy_root(root->kf_root);
cgroup_free_root(root);
@@ -1373,7 +1391,7 @@ static void cgroup_kn_unlock(struct kernfs_node *kn)
else
cgrp = kn->parent->priv;

- mutex_unlock(&cgroup_mutex);
+ cgroup_unlock();

kernfs_unbreak_active_protection(kn);
cgroup_put(cgrp);
@@ -1419,7 +1437,7 @@ static struct cgroup *cgroup_kn_lock_live(struct kernfs_node *kn,
if (drain_offline)
cgroup_lock_and_drain_offline(cgrp);
else
- mutex_lock(&cgroup_mutex);
+ cgroup_lock();

if (!cgroup_is_dead(cgrp))
return cgrp;
@@ -1804,7 +1822,7 @@ static int cgroup_remount(struct kernfs_root *kf_root, int *flags, char *data)
out_unlock:
kfree(opts.release_agent);
kfree(opts.name);
- mutex_unlock(&cgroup_mutex);
+ cgroup_unlock();
return ret;
}

@@ -2045,7 +2063,7 @@ static struct dentry *cgroup_mount(struct file_system_type *fs_type,
continue;

if (!percpu_ref_tryget_live(&ss->root->cgrp.self.refcnt)) {
- mutex_unlock(&cgroup_mutex);
+ cgroup_unlock();
msleep(10);
ret = restart_syscall();
goto out_free;
@@ -2100,7 +2118,7 @@ static struct dentry *cgroup_mount(struct file_system_type *fs_type,
pinned_sb = kernfs_pin_sb(root->kf_root, NULL);
if (IS_ERR(pinned_sb) ||
!percpu_ref_tryget_live(&root->cgrp.self.refcnt)) {
- mutex_unlock(&cgroup_mutex);
+ cgroup_unlock();
if (!IS_ERR_OR_NULL(pinned_sb))
deactivate_super(pinned_sb);
msleep(10);
@@ -2135,7 +2153,7 @@ static struct dentry *cgroup_mount(struct file_system_type *fs_type,
cgroup_free_root(root);

out_unlock:
- mutex_unlock(&cgroup_mutex);
+ cgroup_unlock();
out_free:
kfree(opts.release_agent);
kfree(opts.name);
@@ -2214,7 +2232,7 @@ char *task_cgroup_path(struct task_struct *task, char *buf, size_t buflen)
int hierarchy_id = 1;
char *path = NULL;

- mutex_lock(&cgroup_mutex);
+ cgroup_lock();
spin_lock_bh(&css_set_lock);

root = idr_get_next(&cgroup_hierarchy_idr, &hierarchy_id);
@@ -2229,7 +2247,7 @@ char *task_cgroup_path(struct task_struct *task, char *buf, size_t buflen)
}

spin_unlock_bh(&css_set_lock);
- mutex_unlock(&cgroup_mutex);
+ cgroup_unlock();
return path;
}
EXPORT_SYMBOL_GPL(task_cgroup_path);
@@ -2790,7 +2808,7 @@ int cgroup_attach_task_all(struct task_struct *from, struct task_struct *tsk)
struct cgroup_root *root;
int retval = 0;

- mutex_lock(&cgroup_mutex);
+ cgroup_lock();
for_each_root(root) {
struct cgroup *from_cgrp;

@@ -2805,7 +2823,7 @@ int cgroup_attach_task_all(struct task_struct *from, struct task_struct *tsk)
if (retval)
break;
}
- mutex_unlock(&cgroup_mutex);
+ cgroup_unlock();

return retval;
}
@@ -2968,7 +2986,7 @@ static void cgroup_lock_and_drain_offline(struct cgroup *cgrp)
int ssid;

restart:
- mutex_lock(&cgroup_mutex);
+ cgroup_lock();

cgroup_for_each_live_descendant_post(dsct, d_css, cgrp) {
for_each_subsys(ss, ssid) {
@@ -2982,7 +3000,7 @@ static void cgroup_lock_and_drain_offline(struct cgroup *cgrp)
prepare_to_wait(&dsct->offline_waitq, &wait,
TASK_UNINTERRUPTIBLE);

- mutex_unlock(&cgroup_mutex);
+ cgroup_unlock();
schedule();
finish_wait(&dsct->offline_waitq, &wait);

@@ -3426,11 +3444,11 @@ static int cgroup_rename(struct kernfs_node *kn, struct kernfs_node *new_parent,
kernfs_break_active_protection(new_parent);
kernfs_break_active_protection(kn);

- mutex_lock(&cgroup_mutex);
+ cgroup_lock();

ret = kernfs_rename(kn, new_parent, new_name_str);

- mutex_unlock(&cgroup_mutex);
+ cgroup_unlock();

kernfs_unbreak_active_protection(kn);
kernfs_unbreak_active_protection(new_parent);
@@ -3637,9 +3655,9 @@ int cgroup_rm_cftypes(struct cftype *cfts)
{
int ret;

- mutex_lock(&cgroup_mutex);
+ cgroup_lock();
ret = cgroup_rm_cftypes_locked(cfts);
- mutex_unlock(&cgroup_mutex);
+ cgroup_unlock();
return ret;
}

@@ -3671,14 +3689,14 @@ static int cgroup_add_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
if (ret)
return ret;

- mutex_lock(&cgroup_mutex);
+ cgroup_lock();

list_add_tail(&cfts->node, &ss->cfts);
ret = cgroup_apply_cftypes(cfts, true);
if (ret)
cgroup_rm_cftypes_locked(cfts);

- mutex_unlock(&cgroup_mutex);
+ cgroup_unlock();
return ret;
}

@@ -4170,7 +4188,7 @@ int cgroup_transfer_tasks(struct cgroup *to, struct cgroup *from)
if (!cgroup_may_migrate_to(to))
return -EBUSY;

- mutex_lock(&cgroup_mutex);
+ cgroup_lock();

/* all tasks in @from are being moved, all csets are source */
spin_lock_bh(&css_set_lock);
@@ -4200,7 +4218,7 @@ int cgroup_transfer_tasks(struct cgroup *to, struct cgroup *from)
} while (task && !ret);
out_err:
cgroup_migrate_finish(&preloaded_csets);
- mutex_unlock(&cgroup_mutex);
+ cgroup_unlock();
return ret;
}

@@ -4507,7 +4525,7 @@ int cgroupstats_build(struct cgroupstats *stats, struct dentry *dentry)
kernfs_type(kn) != KERNFS_DIR)
return -EINVAL;

- mutex_lock(&cgroup_mutex);
+ cgroup_lock();

/*
* We aren't being called from kernfs and there's no guarantee on
@@ -4518,7 +4536,7 @@ int cgroupstats_build(struct cgroupstats *stats, struct dentry *dentry)
cgrp = rcu_dereference(kn->priv);
if (!cgrp || cgroup_is_dead(cgrp)) {
rcu_read_unlock();
- mutex_unlock(&cgroup_mutex);
+ cgroup_unlock();
return -ENOENT;
}
rcu_read_unlock();
@@ -4546,7 +4564,7 @@ int cgroupstats_build(struct cgroupstats *stats, struct dentry *dentry)
}
css_task_iter_end(&it);

- mutex_unlock(&cgroup_mutex);
+ cgroup_unlock();
return 0;
}

@@ -4847,7 +4865,7 @@ static void css_release_work_fn(struct work_struct *work)
struct cgroup_subsys *ss = css->ss;
struct cgroup *cgrp = css->cgroup;

- mutex_lock(&cgroup_mutex);
+ cgroup_lock();

css->flags |= CSS_RELEASED;
list_del_rcu(&css->sibling);
@@ -4874,7 +4892,7 @@ static void css_release_work_fn(struct work_struct *work)
NULL);
}

- mutex_unlock(&cgroup_mutex);
+ cgroup_unlock();

call_rcu(&css->rcu_head, css_free_rcu_fn);
}
@@ -5168,7 +5186,7 @@ static void css_killed_work_fn(struct work_struct *work)
struct cgroup_subsys_state *css =
container_of(work, struct cgroup_subsys_state, destroy_work);

- mutex_lock(&cgroup_mutex);
+ cgroup_lock();

do {
offline_css(css);
@@ -5177,7 +5195,7 @@ static void css_killed_work_fn(struct work_struct *work)
css = css->parent;
} while (css && atomic_dec_and_test(&css->online_cnt));

- mutex_unlock(&cgroup_mutex);
+ cgroup_unlock();
}

/* css kill confirmation processing requires process context, bounce */
@@ -5330,7 +5348,7 @@ static void __init cgroup_init_subsys(struct cgroup_subsys *ss, bool early)

pr_debug("Initializing cgroup subsys %s\n", ss->name);

- mutex_lock(&cgroup_mutex);
+ cgroup_lock();

idr_init(&ss->css_idr);
INIT_LIST_HEAD(&ss->cfts);
@@ -5374,7 +5392,7 @@ static void __init cgroup_init_subsys(struct cgroup_subsys *ss, bool early)

BUG_ON(online_css(css));

- mutex_unlock(&cgroup_mutex);
+ cgroup_unlock();
}

/**
@@ -5431,7 +5449,7 @@ int __init cgroup_init(void)
BUG_ON(cgroup_init_cftypes(NULL, cgroup_dfl_base_files));
BUG_ON(cgroup_init_cftypes(NULL, cgroup_legacy_base_files));

- mutex_lock(&cgroup_mutex);
+ cgroup_lock();

/*
* Add init_css_set to the hash table so that dfl_root can link to
@@ -5442,7 +5460,7 @@ int __init cgroup_init(void)

BUG_ON(cgroup_setup_root(&cgrp_dfl_root, 0));

- mutex_unlock(&cgroup_mutex);
+ cgroup_unlock();

for_each_subsys(ss, ssid) {
if (ss->early_init) {
@@ -5548,7 +5566,7 @@ int proc_cgroup_show(struct seq_file *m, struct pid_namespace *ns,
if (!buf)
goto out;

- mutex_lock(&cgroup_mutex);
+ cgroup_lock();
spin_lock_bh(&css_set_lock);

for_each_root(root) {
@@ -5602,7 +5620,7 @@ int proc_cgroup_show(struct seq_file *m, struct pid_namespace *ns,
retval = 0;
out_unlock:
spin_unlock_bh(&css_set_lock);
- mutex_unlock(&cgroup_mutex);
+ cgroup_unlock();
kfree(buf);
out:
return retval;
@@ -5620,7 +5638,7 @@ static int proc_cgroupstats_show(struct seq_file *m, void *v)
* cgroup_mutex is also necessary to guarantee an atomic snapshot of
* subsys/hierarchy state.
*/
- mutex_lock(&cgroup_mutex);
+ cgroup_lock();

for_each_subsys(ss, i)
seq_printf(m, "%s\t%d\t%d\t%d\n",
@@ -5628,7 +5646,7 @@ static int proc_cgroupstats_show(struct seq_file *m, void *v)
atomic_read(&ss->root->nr_cgrps),
cgroup_ssid_enabled(i));

- mutex_unlock(&cgroup_mutex);
+ cgroup_unlock();
return 0;
}

@@ -5860,7 +5878,7 @@ static void cgroup_release_agent(struct work_struct *work)
char *pathbuf = NULL, *agentbuf = NULL, *path;
char *argv[3], *envp[3];

- mutex_lock(&cgroup_mutex);
+ cgroup_lock();

pathbuf = kmalloc(PATH_MAX, GFP_KERNEL);
agentbuf = kstrdup(cgrp->root->release_agent_path, GFP_KERNEL);
@@ -5880,11 +5898,11 @@ static void cgroup_release_agent(struct work_struct *work)
envp[1] = "PATH=/sbin:/bin:/usr/sbin:/usr/bin";
envp[2] = NULL;

- mutex_unlock(&cgroup_mutex);
+ cgroup_unlock();
call_usermodehelper(argv[0], argv, envp, UMH_WAIT_EXEC);
goto out_free;
out:
- mutex_unlock(&cgroup_mutex);
+ cgroup_unlock();
out_free:
kfree(agentbuf);
kfree(pathbuf);
@@ -6006,7 +6024,7 @@ struct cgroup *cgroup_get_from_path(const char *path)
struct kernfs_node *kn;
struct cgroup *cgrp;

- mutex_lock(&cgroup_mutex);
+ cgroup_lock();

kn = kernfs_walk_and_get(cgrp_dfl_root.cgrp.kn, path);
if (kn) {
@@ -6021,7 +6039,7 @@ struct cgroup *cgroup_get_from_path(const char *path)
cgrp = ERR_PTR(-ENOENT);
}

- mutex_unlock(&cgroup_mutex);
+ cgroup_unlock();
return cgrp;
}
EXPORT_SYMBOL_GPL(cgroup_get_from_path);
--
2.5.0

Next message: Michal Hocko: "Re: [PATCH] mm: memcontrol: zap task_struct->memcg_oom_{gfp_mask,order}"
Previous message: Tejun Heo: "[PATCH 05/10] cgroup, fork: add @new_rgrp_cset[p] and @clone_flags to cgroup fork callbacks"
In reply to: Tejun Heo: "[PATCH 05/10] cgroup, fork: add @new_rgrp_cset[p] and @clone_flags to cgroup fork callbacks"
Next in thread: Tejun Heo: "Example program for PRIO_RGRP"
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