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authorTejun Heo <tj@kernel.org>2013-11-29 10:42:59 -0500
committerTejun Heo <tj@kernel.org>2013-11-29 10:42:59 -0500
commite6b817103d168a76e4044ebcdbc08225d77a81cb (patch)
tree2bb6a201b17387f933fea715253f432ef0c7bc81 /kernel/cgroup.c
parent62236858f3cc558135d1ab6b2af44d22c489bb7f (diff)
downloadop-kernel-dev-e6b817103d168a76e4044ebcdbc08225d77a81cb.zip
op-kernel-dev-e6b817103d168a76e4044ebcdbc08225d77a81cb.tar.gz
cgroup: refactor cgroup_pidlist_find()
Rename cgroup_pidlist_find() to cgroup_pidlist_find_create() and separate out finding proper to cgroup_pidlist_find(). Also, move locking to the caller. This patch is preparation for pidlist restructure and doesn't introduce any behavior changes. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
Diffstat (limited to 'kernel/cgroup.c')
-rw-r--r--kernel/cgroup.c65
1 files changed, 38 insertions, 27 deletions
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index ef019c0..d58c30d 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -3575,48 +3575,50 @@ static int cmppid(const void *a, const void *b)
return *(pid_t *)a - *(pid_t *)b;
}
+static struct cgroup_pidlist *cgroup_pidlist_find(struct cgroup *cgrp,
+ enum cgroup_filetype type)
+{
+ struct cgroup_pidlist *l;
+ /* don't need task_nsproxy() if we're looking at ourself */
+ struct pid_namespace *ns = task_active_pid_ns(current);
+
+ lockdep_assert_held(&cgrp->pidlist_mutex);
+
+ list_for_each_entry(l, &cgrp->pidlists, links)
+ if (l->key.type == type && l->key.ns == ns)
+ return l;
+ return NULL;
+}
+
/*
* find the appropriate pidlist for our purpose (given procs vs tasks)
* returns with the lock on that pidlist already held, and takes care
* of the use count, or returns NULL with no locks held if we're out of
* memory.
*/
-static struct cgroup_pidlist *cgroup_pidlist_find(struct cgroup *cgrp,
- enum cgroup_filetype type)
+static struct cgroup_pidlist *cgroup_pidlist_find_create(struct cgroup *cgrp,
+ enum cgroup_filetype type)
{
struct cgroup_pidlist *l;
- /* don't need task_nsproxy() if we're looking at ourself */
- struct pid_namespace *ns = task_active_pid_ns(current);
- /*
- * We can't drop the pidlist_mutex before taking the l->rwsem in case
- * the last ref-holder is trying to remove l from the list at the same
- * time. Holding the pidlist_mutex precludes somebody taking whichever
- * list we find out from under us - compare release_pid_array().
- */
- mutex_lock(&cgrp->pidlist_mutex);
- list_for_each_entry(l, &cgrp->pidlists, links) {
- if (l->key.type == type && l->key.ns == ns) {
- /* make sure l doesn't vanish out from under us */
- down_write(&l->rwsem);
- mutex_unlock(&cgrp->pidlist_mutex);
- return l;
- }
- }
+ lockdep_assert_held(&cgrp->pidlist_mutex);
+
+ l = cgroup_pidlist_find(cgrp, type);
+ if (l)
+ return l;
+
/* entry not found; create a new one */
l = kzalloc(sizeof(struct cgroup_pidlist), GFP_KERNEL);
- if (!l) {
- mutex_unlock(&cgrp->pidlist_mutex);
+ if (!l)
return l;
- }
+
init_rwsem(&l->rwsem);
INIT_DELAYED_WORK(&l->destroy_dwork, cgroup_pidlist_destroy_work_fn);
- down_write(&l->rwsem);
l->key.type = type;
- l->key.ns = get_pid_ns(ns);
+ /* don't need task_nsproxy() if we're looking at ourself */
+ l->key.ns = get_pid_ns(task_active_pid_ns(current));
l->owner = cgrp;
list_add(&l->links, &cgrp->pidlists);
- mutex_unlock(&cgrp->pidlist_mutex);
return l;
}
@@ -3662,17 +3664,26 @@ static int pidlist_array_load(struct cgroup *cgrp, enum cgroup_filetype type,
sort(array, length, sizeof(pid_t), cmppid, NULL);
if (type == CGROUP_FILE_PROCS)
length = pidlist_uniq(array, length);
- l = cgroup_pidlist_find(cgrp, type);
+
+ mutex_lock(&cgrp->pidlist_mutex);
+
+ l = cgroup_pidlist_find_create(cgrp, type);
if (!l) {
+ mutex_unlock(&cgrp->pidlist_mutex);
pidlist_free(array);
return -ENOMEM;
}
- /* store array, freeing old if necessary - lock already held */
+
+ /* store array, freeing old if necessary */
+ down_write(&l->rwsem);
pidlist_free(l->list);
l->list = array;
l->length = length;
l->use_count++;
up_write(&l->rwsem);
+
+ mutex_unlock(&cgrp->pidlist_mutex);
+
*lp = l;
return 0;
}
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