/*
- * kernel/cgroup.c
- *
* Generic process-grouping system.
*
* Based originally on the cpuset system, extracted by Paul Menage
ROOT_NOPREFIX, /* mounted subsystems have no named prefix */
};
-inline int cgroup_is_releasable(const struct cgroup *cgrp)
+static int cgroup_is_releasable(const struct cgroup *cgrp)
{
const int bits =
(1 << CGRP_RELEASABLE) |
return (cgrp->flags & bits) == bits;
}
-inline int notify_on_release(const struct cgroup *cgrp)
+static int notify_on_release(const struct cgroup *cgrp)
{
return test_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
}
* Any task can increment and decrement the count field without lock.
* So in general, code holding cgroup_mutex can't rely on the count
* field not changing. However, if the count goes to zero, then only
- * attach_task() can increment it again. Because a count of zero
+ * cgroup_attach_task() can increment it again. Because a count of zero
* means that no tasks are currently attached, therefore there is no
* way a task attached to that cgroup can fork (the other way to
* increment the count). So code holding cgroup_mutex can safely
* The task_lock() exception
*
* The need for this exception arises from the action of
- * attach_task(), which overwrites one tasks cgroup pointer with
+ * cgroup_attach_task(), which overwrites one tasks cgroup pointer with
* another. It does so using cgroup_mutexe, however there are
* several performance critical places that need to reference
* task->cgroup without the expense of grabbing a system global
* mutex. Therefore except as noted below, when dereferencing or, as
- * in attach_task(), modifying a task'ss cgroup pointer we use
+ * in cgroup_attach_task(), modifying a task'ss cgroup pointer we use
* task_lock(), which acts on a spinlock (task->alloc_lock) already in
* the task_struct routinely used for such matters.
*
* P.S. One more locking exception. RCU is used to guard the
- * update of a tasks cgroup pointer by attach_task()
+ * update of a tasks cgroup pointer by cgroup_attach_task()
*/
/**
return inode;
}
+/*
+ * Call subsys's pre_destroy handler.
+ * This is called before css refcnt check.
+ */
+
+static void cgroup_call_pre_destroy(struct cgroup *cgrp)
+{
+ struct cgroup_subsys *ss;
+ for_each_subsys(cgrp->root, ss)
+ if (ss->pre_destroy && cgrp->subsys[ss->subsys_id])
+ ss->pre_destroy(ss, cgrp);
+ return;
+}
+
+
static void cgroup_diput(struct dentry *dentry, struct inode *inode)
{
/* is dentry a directory ? if so, kfree() associated cgroup */
if (S_ISDIR(inode->i_mode)) {
struct cgroup *cgrp = dentry->d_fsdata;
+ struct cgroup_subsys *ss;
BUG_ON(!(cgroup_is_removed(cgrp)));
/* It's possible for external users to be holding css
* reference counts on a cgroup; css_put() needs to
* queue the cgroup to be handled by the release
* agent */
synchronize_rcu();
+
+ mutex_lock(&cgroup_mutex);
+ /*
+ * Release the subsystem state objects.
+ */
+ for_each_subsys(cgrp->root, ss) {
+ if (cgrp->subsys[ss->subsys_id])
+ ss->destroy(ss, cgrp);
+ }
+
+ cgrp->root->number_of_cgroups--;
+ mutex_unlock(&cgroup_mutex);
+
+ /* Drop the active superblock reference that we took when we
+ * created the cgroup */
+ deactivate_super(cgrp->root->sb);
+
kfree(cgrp);
}
iput(inode);
* Call holding cgroup_mutex. May take task_lock of
* the task 'pid' during call.
*/
-static int attach_task(struct cgroup *cgrp, struct task_struct *tsk)
+int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk)
{
int retval = 0;
struct cgroup_subsys *ss;
for_each_subsys(root, ss) {
if (ss->can_attach) {
retval = ss->can_attach(ss, cgrp, tsk);
- if (retval) {
+ if (retval)
return retval;
- }
}
}
* based on its final set of cgroups
*/
newcg = find_css_set(cg, cgrp);
- if (!newcg) {
+ if (!newcg)
return -ENOMEM;
- }
task_lock(tsk);
if (tsk->flags & PF_EXITING) {
write_unlock(&css_set_lock);
for_each_subsys(root, ss) {
- if (ss->attach) {
+ if (ss->attach)
ss->attach(ss, cgrp, oldcgrp, tsk);
- }
}
set_bit(CGRP_RELEASABLE, &oldcgrp->flags);
synchronize_rcu();
if (pid) {
rcu_read_lock();
- tsk = find_task_by_pid(pid);
+ tsk = find_task_by_vpid(pid);
if (!tsk || tsk->flags & PF_EXITING) {
rcu_read_unlock();
return -ESRCH;
get_task_struct(tsk);
}
- ret = attach_task(cgrp, tsk);
+ ret = cgroup_attach_task(cgrp, tsk);
put_task_struct(tsk);
return ret;
}
goto out1;
}
buffer[nbytes] = 0; /* nul-terminate */
+ strstrip(buffer); /* strip -just- trailing whitespace */
mutex_lock(&cgroup_mutex);
+ /*
+ * This was already checked for in cgroup_file_write(), but
+ * check again now we're holding cgroup_mutex.
+ */
if (cgroup_is_removed(cgrp)) {
retval = -ENODEV;
goto out2;
clear_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
break;
case FILE_RELEASE_AGENT:
- {
- struct cgroupfs_root *root = cgrp->root;
- /* Strip trailing newline */
- if (nbytes && (buffer[nbytes-1] == '\n')) {
- buffer[nbytes-1] = 0;
- }
- if (nbytes < sizeof(root->release_agent_path)) {
- /* We never write anything other than '\0'
- * into the last char of release_agent_path,
- * so it always remains a NUL-terminated
- * string */
- strncpy(root->release_agent_path, buffer, nbytes);
- root->release_agent_path[nbytes] = 0;
- } else {
- retval = -ENOSPC;
- }
+ BUILD_BUG_ON(sizeof(cgrp->root->release_agent_path) < PATH_MAX);
+ strcpy(cgrp->root->release_agent_path, buffer);
break;
- }
default:
retval = -EINVAL;
goto out2;
struct cftype *cft = __d_cft(file->f_dentry);
struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent);
- if (!cft)
+ if (!cft || cgroup_is_removed(cgrp))
return -ENODEV;
if (cft->write)
return cft->write(cgrp, cft, file, buf, nbytes, ppos);
struct cftype *cft = __d_cft(file->f_dentry);
struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent);
- if (!cft)
+ if (!cft || cgroup_is_removed(cgrp))
return -ENODEV;
if (cft->read)
it->task = cg->tasks.next;
}
+/*
+ * To reduce the fork() overhead for systems that are not actually
+ * using their cgroups capability, we don't maintain the lists running
+ * through each css_set to its tasks until we see the list actually
+ * used - in other words after the first call to cgroup_iter_start().
+ *
+ * The tasklist_lock is not held here, as do_each_thread() and
+ * while_each_thread() are protected by RCU.
+ */
+void cgroup_enable_task_cg_lists(void)
+{
+ struct task_struct *p, *g;
+ write_lock(&css_set_lock);
+ use_task_css_set_links = 1;
+ do_each_thread(g, p) {
+ task_lock(p);
+ if (list_empty(&p->cg_list))
+ list_add(&p->cg_list, &p->cgroups->tasks);
+ task_unlock(p);
+ } while_each_thread(g, p);
+ write_unlock(&css_set_lock);
+}
+
void cgroup_iter_start(struct cgroup *cgrp, struct cgroup_iter *it)
{
/*
* we need to enable the list linking each css_set to its
* tasks, and fix up all existing tasks.
*/
- if (!use_task_css_set_links) {
- struct task_struct *p, *g;
- write_lock(&css_set_lock);
- use_task_css_set_links = 1;
- do_each_thread(g, p) {
- task_lock(p);
- if (list_empty(&p->cg_list))
- list_add(&p->cg_list, &p->cgroups->tasks);
- task_unlock(p);
- } while_each_thread(g, p);
- write_unlock(&css_set_lock);
- }
+ if (!use_task_css_set_links)
+ cgroup_enable_task_cg_lists();
+
read_lock(&css_set_lock);
it->cg_link = &cgrp->css_sets;
cgroup_advance_iter(cgrp, it);
read_unlock(&css_set_lock);
}
+static inline int started_after_time(struct task_struct *t1,
+ struct timespec *time,
+ struct task_struct *t2)
+{
+ int start_diff = timespec_compare(&t1->start_time, time);
+ if (start_diff > 0) {
+ return 1;
+ } else if (start_diff < 0) {
+ return 0;
+ } else {
+ /*
+ * Arbitrarily, if two processes started at the same
+ * time, we'll say that the lower pointer value
+ * started first. Note that t2 may have exited by now
+ * so this may not be a valid pointer any longer, but
+ * that's fine - it still serves to distinguish
+ * between two tasks started (effectively) simultaneously.
+ */
+ return t1 > t2;
+ }
+}
+
+/*
+ * This function is a callback from heap_insert() and is used to order
+ * the heap.
+ * In this case we order the heap in descending task start time.
+ */
+static inline int started_after(void *p1, void *p2)
+{
+ struct task_struct *t1 = p1;
+ struct task_struct *t2 = p2;
+ return started_after_time(t1, &t2->start_time, t2);
+}
+
+/**
+ * cgroup_scan_tasks - iterate though all the tasks in a cgroup
+ * @scan: struct cgroup_scanner containing arguments for the scan
+ *
+ * Arguments include pointers to callback functions test_task() and
+ * process_task().
+ * Iterate through all the tasks in a cgroup, calling test_task() for each,
+ * and if it returns true, call process_task() for it also.
+ * The test_task pointer may be NULL, meaning always true (select all tasks).
+ * Effectively duplicates cgroup_iter_{start,next,end}()
+ * but does not lock css_set_lock for the call to process_task().
+ * The struct cgroup_scanner may be embedded in any structure of the caller's
+ * creation.
+ * It is guaranteed that process_task() will act on every task that
+ * is a member of the cgroup for the duration of this call. This
+ * function may or may not call process_task() for tasks that exit
+ * or move to a different cgroup during the call, or are forked or
+ * move into the cgroup during the call.
+ *
+ * Note that test_task() may be called with locks held, and may in some
+ * situations be called multiple times for the same task, so it should
+ * be cheap.
+ * If the heap pointer in the struct cgroup_scanner is non-NULL, a heap has been
+ * pre-allocated and will be used for heap operations (and its "gt" member will
+ * be overwritten), else a temporary heap will be used (allocation of which
+ * may cause this function to fail).
+ */
+int cgroup_scan_tasks(struct cgroup_scanner *scan)
+{
+ int retval, i;
+ struct cgroup_iter it;
+ struct task_struct *p, *dropped;
+ /* Never dereference latest_task, since it's not refcounted */
+ struct task_struct *latest_task = NULL;
+ struct ptr_heap tmp_heap;
+ struct ptr_heap *heap;
+ struct timespec latest_time = { 0, 0 };
+
+ if (scan->heap) {
+ /* The caller supplied our heap and pre-allocated its memory */
+ heap = scan->heap;
+ heap->gt = &started_after;
+ } else {
+ /* We need to allocate our own heap memory */
+ heap = &tmp_heap;
+ retval = heap_init(heap, PAGE_SIZE, GFP_KERNEL, &started_after);
+ if (retval)
+ /* cannot allocate the heap */
+ return retval;
+ }
+
+ again:
+ /*
+ * Scan tasks in the cgroup, using the scanner's "test_task" callback
+ * to determine which are of interest, and using the scanner's
+ * "process_task" callback to process any of them that need an update.
+ * Since we don't want to hold any locks during the task updates,
+ * gather tasks to be processed in a heap structure.
+ * The heap is sorted by descending task start time.
+ * If the statically-sized heap fills up, we overflow tasks that
+ * started later, and in future iterations only consider tasks that
+ * started after the latest task in the previous pass. This
+ * guarantees forward progress and that we don't miss any tasks.
+ */
+ heap->size = 0;
+ cgroup_iter_start(scan->cg, &it);
+ while ((p = cgroup_iter_next(scan->cg, &it))) {
+ /*
+ * Only affect tasks that qualify per the caller's callback,
+ * if he provided one
+ */
+ if (scan->test_task && !scan->test_task(p, scan))
+ continue;
+ /*
+ * Only process tasks that started after the last task
+ * we processed
+ */
+ if (!started_after_time(p, &latest_time, latest_task))
+ continue;
+ dropped = heap_insert(heap, p);
+ if (dropped == NULL) {
+ /*
+ * The new task was inserted; the heap wasn't
+ * previously full
+ */
+ get_task_struct(p);
+ } else if (dropped != p) {
+ /*
+ * The new task was inserted, and pushed out a
+ * different task
+ */
+ get_task_struct(p);
+ put_task_struct(dropped);
+ }
+ /*
+ * Else the new task was newer than anything already in
+ * the heap and wasn't inserted
+ */
+ }
+ cgroup_iter_end(scan->cg, &it);
+
+ if (heap->size) {
+ for (i = 0; i < heap->size; i++) {
+ struct task_struct *p = heap->ptrs[i];
+ if (i == 0) {
+ latest_time = p->start_time;
+ latest_task = p;
+ }
+ /* Process the task per the caller's callback */
+ scan->process_task(p, scan);
+ put_task_struct(p);
+ }
+ /*
+ * If we had to process any tasks at all, scan again
+ * in case some of them were in the middle of forking
+ * children that didn't get processed.
+ * Not the most efficient way to do it, but it avoids
+ * having to take callback_mutex in the fork path
+ */
+ goto again;
+ }
+ if (heap == &tmp_heap)
+ heap_free(&tmp_heap);
+ return 0;
+}
+
/*
* Stuff for reading the 'tasks' file.
*
while ((tsk = cgroup_iter_next(cgrp, &it))) {
if (unlikely(n == npids))
break;
- pidarray[n++] = task_pid_nr(tsk);
+ pidarray[n++] = task_pid_vnr(tsk);
}
cgroup_iter_end(cgrp, &it);
return n;
* matter, since it can only happen if the cgroup
* has been deleted and hence no longer needs the
* release agent to be called anyway. */
- if (css && atomic_read(&css->refcnt)) {
+ if (css && atomic_read(&css->refcnt))
return 1;
- }
}
return 0;
}
struct cgroup *cgrp = dentry->d_fsdata;
struct dentry *d;
struct cgroup *parent;
- struct cgroup_subsys *ss;
struct super_block *sb;
struct cgroupfs_root *root;
parent = cgrp->parent;
root = cgrp->root;
sb = root->sb;
+ /*
+ * Call pre_destroy handlers of subsys
+ */
+ cgroup_call_pre_destroy(cgrp);
+ /*
+ * Notify subsyses that rmdir() request comes.
+ */
if (cgroup_has_css_refs(cgrp)) {
mutex_unlock(&cgroup_mutex);
return -EBUSY;
}
- for_each_subsys(root, ss) {
- if (cgrp->subsys[ss->subsys_id])
- ss->destroy(ss, cgrp);
- }
-
spin_lock(&release_list_lock);
set_bit(CGRP_REMOVED, &cgrp->flags);
if (!list_empty(&cgrp->release_list))
cgroup_d_remove_dir(d);
dput(d);
- root->number_of_cgroups--;
set_bit(CGRP_RELEASABLE, &parent->flags);
check_for_release(parent);
mutex_unlock(&cgroup_mutex);
- /* Drop the active superblock reference that we took when we
- * created the cgroup */
- deactivate_super(sb);
return 0;
}
{
struct cgroup_subsys_state *css;
struct list_head *l;
- printk(KERN_ERR "Initializing cgroup subsys %s\n", ss->name);
+
+ printk(KERN_INFO "Initializing cgroup subsys %s\n", ss->name);
/* Create the top cgroup state for this subsystem */
ss->root = &rootnode;
BUG_ON(!ss->create);
BUG_ON(!ss->destroy);
if (ss->subsys_id != i) {
- printk(KERN_ERR "Subsys %s id == %d\n",
+ printk(KERN_ERR "cgroup: Subsys %s id == %d\n",
ss->name, ss->subsys_id);
BUG();
}
* - Used for /proc/<pid>/cgroup.
* - No need to task_lock(tsk) on this tsk->cgroup reference, as it
* doesn't really matter if tsk->cgroup changes after we read it,
- * and we take cgroup_mutex, keeping attach_task() from changing it
+ * and we take cgroup_mutex, keeping cgroup_attach_task() from changing it
* anyway. No need to check that tsk->cgroup != NULL, thanks to
* the_top_cgroup_hack in cgroup_exit(), which sets an exiting tasks
* cgroup to top_cgroup.
* A pointer to the shared css_set was automatically copied in
* fork.c by dup_task_struct(). However, we ignore that copy, since
* it was not made under the protection of RCU or cgroup_mutex, so
- * might no longer be a valid cgroup pointer. attach_task() might
+ * might no longer be a valid cgroup pointer. cgroup_attach_task() might
* have already changed current->cgroups, allowing the previously
* referenced cgroup group to be removed and freed.
*
* attach us to a different cgroup, decrementing the count on
* the first cgroup that we never incremented. But in this case,
* top_cgroup isn't going away, and either task has PF_EXITING set,
- * which wards off any attach_task() attempts, or task is a failed
- * fork, never visible to attach_task.
+ * which wards off any cgroup_attach_task() attempts, or task is a failed
+ * fork, never visible to cgroup_attach_task.
*
*/
void cgroup_exit(struct task_struct *tsk, int run_callbacks)
dentry = lookup_one_len(nodename, parent->dentry, strlen(nodename));
if (IS_ERR(dentry)) {
printk(KERN_INFO
- "Couldn't allocate dentry for %s: %ld\n", nodename,
+ "cgroup: Couldn't allocate dentry for %s: %ld\n", nodename,
PTR_ERR(dentry));
ret = PTR_ERR(dentry);
goto out_release;
}
/* All seems fine. Finish by moving the task into the new cgroup */
- ret = attach_task(child, tsk);
+ ret = cgroup_attach_task(child, tsk);
mutex_unlock(&cgroup_mutex);
out_release:
projects / linux-2.6-omap-h63xx.git / blobdiff