cgroup: use cgroup_kn_lock_live() in other cgroup kernfs methods
Make __cgroup_procs_write() and cgroup_release_agent_write() use
cgroup_kn_lock_live() and cgroup_kn_unlock() instead of
cgroup_lock_live_group(). This puts the operations under both
cgroup_tree_mutex and cgroup_mutex protection without circular
dependency from kernfs active protection. Also, this means that
cgroup_mutex is no longer nested below kernfs active protection.
There is no longer any place where the two locks interact.
This leaves cgroup_lock_live_group() without any user. Removed.
This will help simplifying cgroup locking.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 21739e4..b7cd808 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -386,23 +386,6 @@
; \
else
-/**
- * cgroup_lock_live_group - take cgroup_mutex and check that cgrp is alive.
- * @cgrp: the cgroup to be checked for liveness
- *
- * On success, returns true; the mutex should be later unlocked. On
- * failure returns false with no lock held.
- */
-static bool cgroup_lock_live_group(struct cgroup *cgrp)
-{
- mutex_lock(&cgroup_mutex);
- if (cgroup_is_dead(cgrp)) {
- mutex_unlock(&cgroup_mutex);
- return false;
- }
- return true;
-}
-
/* the list of cgroups eligible for automatic release. Protected by
* release_list_lock */
static LIST_HEAD(release_list);
@@ -2306,14 +2289,15 @@
{
struct task_struct *tsk;
const struct cred *cred = current_cred(), *tcred;
- struct cgroup *cgrp = of_css(of)->cgroup;
+ struct cgroup *cgrp;
pid_t pid;
int ret;
if (kstrtoint(strstrip(buf), 0, &pid) || pid < 0)
return -EINVAL;
- if (!cgroup_lock_live_group(cgrp))
+ cgrp = cgroup_kn_lock_live(of->kn);
+ if (!cgrp)
return -ENODEV;
retry_find_task:
@@ -2379,7 +2363,7 @@
put_task_struct(tsk);
out_unlock_cgroup:
- mutex_unlock(&cgroup_mutex);
+ cgroup_kn_unlock(of->kn);
return ret ?: nbytes;
}
@@ -2429,17 +2413,18 @@
static ssize_t cgroup_release_agent_write(struct kernfs_open_file *of,
char *buf, size_t nbytes, loff_t off)
{
- struct cgroup *cgrp = of_css(of)->cgroup;
- struct cgroup_root *root = cgrp->root;
+ struct cgroup *cgrp;
- BUILD_BUG_ON(sizeof(root->release_agent_path) < PATH_MAX);
- if (!cgroup_lock_live_group(cgrp))
+ BUILD_BUG_ON(sizeof(cgrp->root->release_agent_path) < PATH_MAX);
+
+ cgrp = cgroup_kn_lock_live(of->kn);
+ if (!cgrp)
return -ENODEV;
spin_lock(&release_agent_path_lock);
- strlcpy(root->release_agent_path, strstrip(buf),
- sizeof(root->release_agent_path));
+ strlcpy(cgrp->root->release_agent_path, strstrip(buf),
+ sizeof(cgrp->root->release_agent_path));
spin_unlock(&release_agent_path_lock);
- mutex_unlock(&cgroup_mutex);
+ cgroup_kn_unlock(of->kn);
return nbytes;
}
