* Based originally on the cpuset system, extracted by Paul Menage
* Copyright (C) 2006 Google, Inc
*
+ * Notifications support
+ * Copyright (C) 2009 Nokia Corporation
+ * Author: Kirill A. Shutemov
+ *
* Copyright notices from the original cpuset code:
* --------------------------------------------------
* Copyright (C) 2003 BULL SA.
#include <linux/pid_namespace.h>
#include <linux/idr.h>
#include <linux/vmalloc.h> /* TODO: replace with more sophisticated array */
+#include <linux/eventfd.h>
+#include <linux/poll.h>
#include <asm/atomic.h>
unsigned short stack[0]; /* Array of Length (depth+1) */
};
+/*
+ * cgroup_event represents events which userspace want to recieve.
+ */
+struct cgroup_event {
+ /*
+ * Cgroup which the event belongs to.
+ */
+ struct cgroup *cgrp;
+ /*
+ * Control file which the event associated.
+ */
+ struct cftype *cft;
+ /*
+ * eventfd to signal userspace about the event.
+ */
+ struct eventfd_ctx *eventfd;
+ /*
+ * Each of these stored in a list by the cgroup.
+ */
+ struct list_head list;
+ /*
+ * All fields below needed to unregister event when
+ * userspace closes eventfd.
+ */
+ poll_table pt;
+ wait_queue_head_t *wqh;
+ wait_queue_t wait;
+ struct work_struct remove;
+};
/* The list of hierarchy roots */
static int cgroup_call_pre_destroy(struct cgroup *cgrp)
{
struct cgroup_subsys *ss;
+ struct cgroup_event *event, *tmp;
int ret = 0;
for_each_subsys(cgrp->root, ss)
if (ss->pre_destroy) {
ret = ss->pre_destroy(ss, cgrp);
if (ret)
- break;
+ goto out;
}
+
+ /*
+ * Unregister events and notify userspace.
+ */
+ spin_lock(&cgrp->event_list_lock);
+ list_for_each_entry_safe(event, tmp, &cgrp->event_list, list) {
+ list_del(&event->list);
+ eventfd_signal(event->eventfd, 1);
+ schedule_work(&event->remove);
+ }
+ spin_unlock(&cgrp->event_list_lock);
+
+out:
return ret;
}
INIT_LIST_HEAD(&cgrp->release_list);
INIT_LIST_HEAD(&cgrp->pidlists);
mutex_init(&cgrp->pidlist_mutex);
+ INIT_LIST_HEAD(&cgrp->event_list);
+ spin_lock_init(&cgrp->event_list_lock);
}
static void init_cgroup_root(struct cgroupfs_root *root)
.rename = cgroup_rename,
};
+/*
+ * Check if a file is a control file
+ */
+static inline struct cftype *__file_cft(struct file *file)
+{
+ if (file->f_dentry->d_inode->i_fop != &cgroup_file_operations)
+ return ERR_PTR(-EINVAL);
+ return __d_cft(file->f_dentry);
+}
+
static int cgroup_create_file(struct dentry *dentry, mode_t mode,
struct super_block *sb)
{
}
/*
+ * Unregister event and free resources.
+ *
+ * Gets called from workqueue.
+ */
+static void cgroup_event_remove(struct work_struct *work)
+{
+ struct cgroup_event *event = container_of(work, struct cgroup_event,
+ remove);
+ struct cgroup *cgrp = event->cgrp;
+
+ /* TODO: check return code */
+ event->cft->unregister_event(cgrp, event->cft, event->eventfd);
+
+ eventfd_ctx_put(event->eventfd);
+ remove_wait_queue(event->wqh, &event->wait);
+ kfree(event);
+}
+
+/*
+ * Gets called on POLLHUP on eventfd when user closes it.
+ *
+ * Called with wqh->lock held and interrupts disabled.
+ */
+static int cgroup_event_wake(wait_queue_t *wait, unsigned mode,
+ int sync, void *key)
+{
+ struct cgroup_event *event = container_of(wait,
+ struct cgroup_event, wait);
+ struct cgroup *cgrp = event->cgrp;
+ unsigned long flags = (unsigned long)key;
+
+ if (flags & POLLHUP) {
+ spin_lock(&cgrp->event_list_lock);
+ list_del(&event->list);
+ spin_unlock(&cgrp->event_list_lock);
+ /*
+ * We are in atomic context, but cgroup_event_remove() may
+ * sleep, so we have to call it in workqueue.
+ */
+ schedule_work(&event->remove);
+ }
+
+ return 0;
+}
+
+static void cgroup_event_ptable_queue_proc(struct file *file,
+ wait_queue_head_t *wqh, poll_table *pt)
+{
+ struct cgroup_event *event = container_of(pt,
+ struct cgroup_event, pt);
+
+ event->wqh = wqh;
+ add_wait_queue(wqh, &event->wait);
+}
+
+/*
+ * Parse input and register new cgroup event handler.
+ *
+ * Input must be in format '<event_fd> <control_fd> <args>'.
+ * Interpretation of args is defined by control file implementation.
+ */
+static int cgroup_write_event_control(struct cgroup *cgrp, struct cftype *cft,
+ const char *buffer)
+{
+ struct cgroup_event *event = NULL;
+ unsigned int efd, cfd;
+ struct file *efile = NULL;
+ struct file *cfile = NULL;
+ char *endp;
+ int ret;
+
+ efd = simple_strtoul(buffer, &endp, 10);
+ if (*endp != ' ')
+ return -EINVAL;
+ buffer = endp + 1;
+
+ cfd = simple_strtoul(buffer, &endp, 10);
+ if ((*endp != ' ') && (*endp != '\0'))
+ return -EINVAL;
+ buffer = endp + 1;
+
+ event = kzalloc(sizeof(*event), GFP_KERNEL);
+ if (!event)
+ return -ENOMEM;
+ event->cgrp = cgrp;
+ INIT_LIST_HEAD(&event->list);
+ init_poll_funcptr(&event->pt, cgroup_event_ptable_queue_proc);
+ init_waitqueue_func_entry(&event->wait, cgroup_event_wake);
+ INIT_WORK(&event->remove, cgroup_event_remove);
+
+ efile = eventfd_fget(efd);
+ if (IS_ERR(efile)) {
+ ret = PTR_ERR(efile);
+ goto fail;
+ }
+
+ event->eventfd = eventfd_ctx_fileget(efile);
+ if (IS_ERR(event->eventfd)) {
+ ret = PTR_ERR(event->eventfd);
+ goto fail;
+ }
+
+ cfile = fget(cfd);
+ if (!cfile) {
+ ret = -EBADF;
+ goto fail;
+ }
+
+ /* the process need read permission on control file */
+ ret = file_permission(cfile, MAY_READ);
+ if (ret < 0)
+ goto fail;
+
+ event->cft = __file_cft(cfile);
+ if (IS_ERR(event->cft)) {
+ ret = PTR_ERR(event->cft);
+ goto fail;
+ }
+
+ if (!event->cft->register_event || !event->cft->unregister_event) {
+ ret = -EINVAL;
+ goto fail;
+ }
+
+ ret = event->cft->register_event(cgrp, event->cft,
+ event->eventfd, buffer);
+ if (ret)
+ goto fail;
+
+ if (efile->f_op->poll(efile, &event->pt) & POLLHUP) {
+ event->cft->unregister_event(cgrp, event->cft, event->eventfd);
+ ret = 0;
+ goto fail;
+ }
+
+ spin_lock(&cgrp->event_list_lock);
+ list_add(&event->list, &cgrp->event_list);
+ spin_unlock(&cgrp->event_list_lock);
+
+ fput(cfile);
+ fput(efile);
+
+ return 0;
+
+fail:
+ if (cfile)
+ fput(cfile);
+
+ if (event && event->eventfd && !IS_ERR(event->eventfd))
+ eventfd_ctx_put(event->eventfd);
+
+ if (!IS_ERR_OR_NULL(efile))
+ fput(efile);
+
+ kfree(event);
+
+ return ret;
+}
+
+/*
* for the common functions, 'private' gives the type of file
*/
/* for hysterical raisins, we can't put this on the older files */
.read_u64 = cgroup_read_notify_on_release,
.write_u64 = cgroup_write_notify_on_release,
},
+ {
+ .name = CGROUP_FILE_GENERIC_PREFIX "event_control",
+ .write_string = cgroup_write_event_control,
+ .mode = S_IWUGO,
+ },
};
static struct cftype cft_release_agent = {
git://ftp.safe.ca / safe / jmp / linux-2.6 / commitdiff