#include <linux/hash.h>
#include <linux/namei.h>
#include <linux/smp_lock.h>
+#include <linux/pid_namespace.h>
#include <asm/atomic.h>
* reference to css->refcnt. In general, this refcnt is expected to goes down
* to zero, soon.
*
- * CGRP_WAIT_ON_RMDIR flag is modified under cgroup's inode->i_mutex;
+ * CGRP_WAIT_ON_RMDIR flag is set under cgroup's inode->i_mutex;
*/
DECLARE_WAIT_QUEUE_HEAD(cgroup_rmdir_waitq);
-static void cgroup_wakeup_rmdir_waiters(const struct cgroup *cgrp)
+static void cgroup_wakeup_rmdir_waiter(struct cgroup *cgrp)
{
- if (unlikely(test_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags)))
+ if (unlikely(test_and_clear_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags)))
wake_up_all(&cgroup_rmdir_waitq);
}
+void cgroup_exclude_rmdir(struct cgroup_subsys_state *css)
+{
+ css_get(css);
+}
+
+void cgroup_release_and_wakeup_rmdir(struct cgroup_subsys_state *css)
+{
+ cgroup_wakeup_rmdir_waiter(css->cgroup);
+ css_put(css);
+}
+
+
static int rebind_subsystems(struct cgroupfs_root *root,
unsigned long final_bits)
{
INIT_LIST_HEAD(&cgrp->children);
INIT_LIST_HEAD(&cgrp->css_sets);
INIT_LIST_HEAD(&cgrp->release_list);
+ INIT_LIST_HEAD(&cgrp->pids_list);
init_rwsem(&cgrp->pids_mutex);
}
static void init_cgroup_root(struct cgroupfs_root *root)
* wake up rmdir() waiter. the rmdir should fail since the cgroup
* is no longer empty.
*/
- cgroup_wakeup_rmdir_waiters(cgrp);
+ cgroup_wakeup_rmdir_waiter(cgrp);
return 0;
}
return ret;
}
+/*
+ * Cache pids for all threads in the same pid namespace that are
+ * opening the same "tasks" file.
+ */
+struct cgroup_pids {
+ /* The node in cgrp->pids_list */
+ struct list_head list;
+ /* The cgroup those pids belong to */
+ struct cgroup *cgrp;
+ /* The namepsace those pids belong to */
+ struct pid_namespace *ns;
+ /* Array of process ids in the cgroup */
+ pid_t *tasks_pids;
+ /* How many files are using the this tasks_pids array */
+ int use_count;
+ /* Length of the current tasks_pids array */
+ int length;
+};
+
static int cmppid(const void *a, const void *b)
{
return *(pid_t *)a - *(pid_t *)b;
}
-
/*
* seq_file methods for the "tasks" file. The seq_file position is the
* next pid to display; the seq_file iterator is a pointer to the pid
* after a seek to the start). Use a binary-search to find the
* next pid to display, if any
*/
- struct cgroup *cgrp = s->private;
+ struct cgroup_pids *cp = s->private;
+ struct cgroup *cgrp = cp->cgrp;
int index = 0, pid = *pos;
int *iter;
down_read(&cgrp->pids_mutex);
if (pid) {
- int end = cgrp->pids_length;
+ int end = cp->length;
while (index < end) {
int mid = (index + end) / 2;
- if (cgrp->tasks_pids[mid] == pid) {
+ if (cp->tasks_pids[mid] == pid) {
index = mid;
break;
- } else if (cgrp->tasks_pids[mid] <= pid)
+ } else if (cp->tasks_pids[mid] <= pid)
index = mid + 1;
else
end = mid;
}
}
/* If we're off the end of the array, we're done */
- if (index >= cgrp->pids_length)
+ if (index >= cp->length)
return NULL;
/* Update the abstract position to be the actual pid that we found */
- iter = cgrp->tasks_pids + index;
+ iter = cp->tasks_pids + index;
*pos = *iter;
return iter;
}
static void cgroup_tasks_stop(struct seq_file *s, void *v)
{
- struct cgroup *cgrp = s->private;
+ struct cgroup_pids *cp = s->private;
+ struct cgroup *cgrp = cp->cgrp;
up_read(&cgrp->pids_mutex);
}
static void *cgroup_tasks_next(struct seq_file *s, void *v, loff_t *pos)
{
- struct cgroup *cgrp = s->private;
+ struct cgroup_pids *cp = s->private;
int *p = v;
- int *end = cgrp->tasks_pids + cgrp->pids_length;
+ int *end = cp->tasks_pids + cp->length;
/*
* Advance to the next pid in the array. If this goes off the
.show = cgroup_tasks_show,
};
-static void release_cgroup_pid_array(struct cgroup *cgrp)
+static void release_cgroup_pid_array(struct cgroup_pids *cp)
{
+ struct cgroup *cgrp = cp->cgrp;
+
down_write(&cgrp->pids_mutex);
- BUG_ON(!cgrp->pids_use_count);
- if (!--cgrp->pids_use_count) {
- kfree(cgrp->tasks_pids);
- cgrp->tasks_pids = NULL;
- cgrp->pids_length = 0;
+ BUG_ON(!cp->use_count);
+ if (!--cp->use_count) {
+ list_del(&cp->list);
+ put_pid_ns(cp->ns);
+ kfree(cp->tasks_pids);
+ kfree(cp);
}
up_write(&cgrp->pids_mutex);
}
static int cgroup_tasks_release(struct inode *inode, struct file *file)
{
- struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent);
+ struct seq_file *seq;
+ struct cgroup_pids *cp;
if (!(file->f_mode & FMODE_READ))
return 0;
- release_cgroup_pid_array(cgrp);
+ seq = file->private_data;
+ cp = seq->private;
+
+ release_cgroup_pid_array(cp);
return seq_release(inode, file);
}
static int cgroup_tasks_open(struct inode *unused, struct file *file)
{
struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent);
+ struct pid_namespace *ns = current->nsproxy->pid_ns;
+ struct cgroup_pids *cp;
pid_t *pidarray;
int npids;
int retval;
* array if necessary
*/
down_write(&cgrp->pids_mutex);
- kfree(cgrp->tasks_pids);
- cgrp->tasks_pids = pidarray;
- cgrp->pids_length = npids;
- cgrp->pids_use_count++;
+
+ list_for_each_entry(cp, &cgrp->pids_list, list) {
+ if (ns == cp->ns)
+ goto found;
+ }
+
+ cp = kzalloc(sizeof(*cp), GFP_KERNEL);
+ if (!cp) {
+ up_write(&cgrp->pids_mutex);
+ kfree(pidarray);
+ return -ENOMEM;
+ }
+ cp->cgrp = cgrp;
+ cp->ns = ns;
+ get_pid_ns(ns);
+ list_add(&cp->list, &cgrp->pids_list);
+found:
+ kfree(cp->tasks_pids);
+ cp->tasks_pids = pidarray;
+ cp->length = npids;
+ cp->use_count++;
up_write(&cgrp->pids_mutex);
file->f_op = &cgroup_tasks_operations;
retval = seq_open(file, &cgroup_tasks_seq_operations);
if (retval) {
- release_cgroup_pid_array(cgrp);
+ release_cgroup_pid_array(cp);
return retval;
}
- ((struct seq_file *)file->private_data)->private = cgrp;
+ ((struct seq_file *)file->private_data)->private = cp;
return 0;
}
}
mutex_unlock(&cgroup_mutex);
+ /*
+ * In general, subsystem has no css->refcnt after pre_destroy(). But
+ * in racy cases, subsystem may have to get css->refcnt after
+ * pre_destroy() and it makes rmdir return with -EBUSY. This sometimes
+ * make rmdir return -EBUSY too often. To avoid that, we use waitqueue
+ * for cgroup's rmdir. CGRP_WAIT_ON_RMDIR is for synchronizing rmdir
+ * and subsystem's reference count handling. Please see css_get/put
+ * and css_tryget() and cgroup_wakeup_rmdir_waiter() implementation.
+ */
+ set_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags);
+
/*
* Call pre_destroy handlers of subsys. Notify subsystems
* that rmdir() request comes.
*/
ret = cgroup_call_pre_destroy(cgrp);
- if (ret)
+ if (ret) {
+ clear_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags);
return ret;
+ }
mutex_lock(&cgroup_mutex);
parent = cgrp->parent;
if (atomic_read(&cgrp->count) || !list_empty(&cgrp->children)) {
+ clear_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags);
mutex_unlock(&cgroup_mutex);
return -EBUSY;
}
- /*
- * css_put/get is provided for subsys to grab refcnt to css. In typical
- * case, subsystem has no reference after pre_destroy(). But, under
- * hierarchy management, some *temporal* refcnt can be hold.
- * To avoid returning -EBUSY to a user, waitqueue is used. If subsys
- * is really busy, it should return -EBUSY at pre_destroy(). wake_up
- * is called when css_put() is called and refcnt goes down to 0.
- */
- set_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags);
prepare_to_wait(&cgroup_rmdir_waitq, &wait, TASK_INTERRUPTIBLE);
-
if (!cgroup_clear_css_refs(cgrp)) {
mutex_unlock(&cgroup_mutex);
- schedule();
+ /*
+ * Because someone may call cgroup_wakeup_rmdir_waiter() before
+ * prepare_to_wait(), we need to check this flag.
+ */
+ if (test_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags))
+ schedule();
finish_wait(&cgroup_rmdir_waitq, &wait);
clear_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags);
if (signal_pending(current))
set_bit(CGRP_RELEASABLE, &cgrp->flags);
check_for_release(cgrp);
}
- cgroup_wakeup_rmdir_waiters(cgrp);
+ cgroup_wakeup_rmdir_waiter(cgrp);
}
rcu_read_unlock();
}
git.openpandora.org / pandora-kernel.git / blobdiff