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Message-Id: <20091215183533.1a1e87d9.kamezawa.hiroyu@jp.fujitsu.com>
Date: Tue, 15 Dec 2009 18:35:33 +0900
From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To: "Kirill A. Shutemov" <kirill@...temov.name>
Cc: Paul Menage <menage@...gle.com>, Li Zefan <lizf@...fujitsu.com>,
containers@...ts.linux-foundation.org,
Andrew Morton <akpm@...ux-foundation.org>,
Balbir Singh <balbir@...ux.vnet.ibm.com>,
Pavel Emelyanov <xemul@...nvz.org>,
Dan Malek <dan@...eddedalley.com>,
Vladislav Buzov <vbuzov@...eddedalley.com>,
Daisuke Nishimura <nishimura@....nes.nec.co.jp>,
linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH RFC v2 1/4] cgroup: implement eventfd-based generic API
for notifications
On Tue, 15 Dec 2009 11:11:16 +0200
"Kirill A. Shutemov" <kirill@...temov.name> wrote:
> Could anybody review the patch?
>
> Thank you.
some nitpicks.
>
> On Sat, Dec 12, 2009 at 12:59 AM, Kirill A. Shutemov
> <kirill@...temov.name> wrote:
> > + /*
> > + * Unregister events and notify userspace.
> > + * FIXME: How to avoid race with cgroup_event_remove_work()
> > + * which runs from workqueue?
> > + */
> > + mutex_lock(&cgrp->event_list_mutex);
> > + list_for_each_entry_safe(event, tmp, &cgrp->event_list, list) {
> > + cgroup_event_remove(event);
> > + eventfd_signal(event->eventfd, 1);
> > + }
> > + mutex_unlock(&cgrp->event_list_mutex);
> > +
> > +out:
> > return ret;
> > }
How ciritical is this FIXME ?
But Hmm..can't we use RCU ?
> >
> > @@ -1136,6 +1187,8 @@ static void init_cgroup_housekeeping(struct cgroup *cgrp)
> > INIT_LIST_HEAD(&cgrp->release_list);
> > INIT_LIST_HEAD(&cgrp->pidlists);
> > mutex_init(&cgrp->pidlist_mutex);
> > + INIT_LIST_HEAD(&cgrp->event_list);
> > + mutex_init(&cgrp->event_list_mutex);
> > }
> >
> > static void init_cgroup_root(struct cgroupfs_root *root)
> > @@ -1935,6 +1988,16 @@ static const struct inode_operations cgroup_dir_inode_operations = {
> > .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)
> > {
> > @@ -2789,6 +2852,151 @@ static int cgroup_write_notify_on_release(struct cgroup *cgrp,
> > return 0;
> > }
> >
> > +static inline void cgroup_event_remove(struct cgroup_event *event)
> > +{
> > + struct cgroup *cgrp = event->cgrp;
> > +
> > + BUG_ON(event->cft->unregister_event(cgrp, event->cft, event->eventfd));
Hmm ? BUG ? If bug, please add document or comment.
> > + eventfd_ctx_put(event->eventfd);
> > + remove_wait_queue(event->wqh, &event->wait);
> > + list_del(&event->list);
please add comment as /* event_list_mutex must be held */
> > + kfree(event);
> > +}
> > +
> > +static void cgroup_event_remove_work(struct work_struct *work)
> > +{
> > + struct cgroup_event *event = container_of(work, struct cgroup_event,
> > + remove);
> > + struct cgroup *cgrp = event->cgrp;
> > +
> > + mutex_lock(&cgrp->event_list_mutex);
> > + cgroup_event_remove(event);
> > + mutex_unlock(&cgrp->event_list_mutex);
> > +}
> > +
> > +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);
> > + unsigned long flags = (unsigned long)key;
> > +
> > + if (flags & POLLHUP)
> > + /*
> > + * This function called with spinlock taken, but
> > + * cgroup_event_remove() may sleep, so we have
> > + * to run it in a 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);
> > +}
> > +
> > +static int cgroup_write_event_control(struct cgroup *cont, 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 = cont;
> > + 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_work);
> > +
> > + 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(cont, event->cft,
> > + event->eventfd, buffer);
> > + if (ret)
> > + goto fail;
> > +
> > + efile->f_op->poll(efile, &event->pt);
Not necessary to check return value ?
Thanks,
-Kame
> > +
> > + mutex_lock(&cont->event_list_mutex);
> > + list_add(&event->list, &cont->event_list);
> > + mutex_unlock(&cont->event_list_mutex);
> > +
> > + fput(cfile);
> > + fput(efile);
> > +
> > + return 0;
> > +
> > +fail:
> > + if (!IS_ERR(cfile))
> > + fput(cfile);
> > +
> > + if (event && event->eventfd && !IS_ERR(event->eventfd))
> > + eventfd_ctx_put(event->eventfd);
> > +
> > + if (!IS_ERR(efile))
> > + fput(efile);
> > +
> > + if (event)
> > + kfree(event);
> > +
> > + return ret;
> > +}
> > +
> > /*
> > * for the common functions, 'private' gives the type of file
> > */
> > @@ -2814,6 +3022,11 @@ static struct cftype 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 = {
> > --
> > 1.6.5.3
> >
> >
>
> --
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