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-rw-r--r--kernel/cgroup/cgroup.c26
1 files changed, 20 insertions, 6 deletions
diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index d0725c1a8db5..881ce1470beb 100644
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -68,6 +68,14 @@
#define CGROUP_FILE_NOTIFY_MIN_INTV DIV_ROUND_UP(HZ, 100)
/*
+ * To avoid confusing the compiler (and generating warnings) with code
+ * that attempts to access what would be a 0-element array (i.e. sized
+ * to a potentially empty array when CGROUP_SUBSYS_COUNT == 0), this
+ * constant expression can be added.
+ */
+#define CGROUP_HAS_SUBSYS_CONFIG (CGROUP_SUBSYS_COUNT > 0)
+
+/*
* cgroup_mutex is the master lock. Any modification to cgroup or its
* hierarchy must be performed while holding it.
*
@@ -248,7 +256,7 @@ static int cgroup_addrm_files(struct cgroup_subsys_state *css,
*/
bool cgroup_ssid_enabled(int ssid)
{
- if (CGROUP_SUBSYS_COUNT == 0)
+ if (!CGROUP_HAS_SUBSYS_CONFIG)
return false;
return static_key_enabled(cgroup_subsys_enabled_key[ssid]);
@@ -472,7 +480,7 @@ static u16 cgroup_ss_mask(struct cgroup *cgrp)
static struct cgroup_subsys_state *cgroup_css(struct cgroup *cgrp,
struct cgroup_subsys *ss)
{
- if (ss)
+ if (CGROUP_HAS_SUBSYS_CONFIG && ss)
return rcu_dereference_check(cgrp->subsys[ss->id],
lockdep_is_held(&cgroup_mutex));
else
@@ -550,6 +558,9 @@ struct cgroup_subsys_state *cgroup_e_css(struct cgroup *cgrp,
{
struct cgroup_subsys_state *css;
+ if (!CGROUP_HAS_SUBSYS_CONFIG)
+ return NULL;
+
do {
css = cgroup_css(cgrp, ss);
@@ -577,6 +588,9 @@ struct cgroup_subsys_state *cgroup_get_e_css(struct cgroup *cgrp,
{
struct cgroup_subsys_state *css;
+ if (!CGROUP_HAS_SUBSYS_CONFIG)
+ return NULL;
+
rcu_read_lock();
do {
@@ -647,7 +661,7 @@ struct cgroup_subsys_state *of_css(struct kernfs_open_file *of)
* the matching css from the cgroup's subsys table is guaranteed to
* be and stay valid until the enclosing operation is complete.
*/
- if (cft->ss)
+ if (CGROUP_HAS_SUBSYS_CONFIG && cft->ss)
return rcu_dereference_raw(cgrp->subsys[cft->ss->id]);
else
return &cgrp->self;
@@ -695,7 +709,7 @@ EXPORT_SYMBOL_GPL(of_css);
*/
#define do_each_subsys_mask(ss, ssid, ss_mask) do { \
unsigned long __ss_mask = (ss_mask); \
- if (!CGROUP_SUBSYS_COUNT) { /* to avoid spurious gcc warning */ \
+ if (!CGROUP_HAS_SUBSYS_CONFIG) { \
(ssid) = 0; \
break; \
} \
@@ -2372,7 +2386,7 @@ struct task_struct *cgroup_taskset_next(struct cgroup_taskset *tset,
struct css_set *cset = tset->cur_cset;
struct task_struct *task = tset->cur_task;
- while (&cset->mg_node != tset->csets) {
+ while (CGROUP_HAS_SUBSYS_CONFIG && &cset->mg_node != tset->csets) {
if (!task)
task = list_first_entry(&cset->mg_tasks,
struct task_struct, cg_list);
@@ -4643,7 +4657,7 @@ void css_task_iter_start(struct cgroup_subsys_state *css, unsigned int flags,
it->ss = css->ss;
it->flags = flags;
- if (it->ss)
+ if (CGROUP_HAS_SUBSYS_CONFIG && it->ss)
it->cset_pos = &css->cgroup->e_csets[css->ss->id];
else
it->cset_pos = &css->cgroup->cset_links;