[Devel] Re: [PATCH] Fixes for cgroup-implement-eventfd-based-generic-api-for-notifications.patch

[Kirill A. Shutemov]

On Fri, Jan 15, 2010 at 7:33 AM, Kirill A. Shutemov
<kirill at shutemov.name> wrote:
> Several random fixes.
>
> Andrew, please fold it in cgroup-implement-eventfd-based-generic-api-for-notifications.patch

Andrew, please, do not miss the patch.

> Signed-off-by: Kirill A. Shutemov <kirill at shutemov.name>
> Cc: Paul Menage <menage at google.com>
> Cc: Li Zefan <lizf at cn.fujitsu.com>
> ---
>  Documentation/cgroups/cgroups.txt |    1 +
>  kernel/cgroup.c                   |   26 +++++++++++++++++++++++---
>  2 files changed, 24 insertions(+), 3 deletions(-)
>
> diff --git a/Documentation/cgroups/cgroups.txt b/Documentation/cgroups/cgroups.txt
> index 5a052ff..47d5100 100644
> --- a/Documentation/cgroups/cgroups.txt
> +++ b/Documentation/cgroups/cgroups.txt
> @@ -23,6 +23,7 @@ CONTENTS:
>   2.1 Basic Usage
>   2.2 Attaching processes
>   2.3 Mounting hierarchies by name
> +  2.4 Notification API
>  3. Kernel API
>   3.1 Overview
>   3.2 Synchronization
> diff --git a/kernel/cgroup.c b/kernel/cgroup.c
> index 44028a9..23315e5 100644
> --- a/kernel/cgroup.c
> +++ b/kernel/cgroup.c
> @@ -2875,13 +2875,18 @@ static int cgroup_write_notify_on_release(struct cgroup *cgrp,
>        return 0;
>  }
>
> +/*
> + * 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*/
> +       /* TODO: check return code */
>        event->cft->unregister_event(cgrp, event->cft, event->eventfd);
>
>        eventfd_ctx_put(event->eventfd);
> @@ -2889,6 +2894,11 @@ static void cgroup_event_remove(struct work_struct *work)
>        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)
>  {
> @@ -2901,6 +2911,10 @@ static int cgroup_event_wake(wait_queue_t *wait, unsigned mode,
>                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);
>        }
>
> @@ -2917,6 +2931,12 @@ static void cgroup_event_ptable_queue_proc(struct file *file,
>        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)
>  {
> @@ -3001,13 +3021,13 @@ static int cgroup_write_event_control(struct cgroup *cgrp, struct cftype *cft,
>        return 0;
>
>  fail:
> -       if (!IS_ERR(cfile))
> +       if (!cfile)
>                fput(cfile);
>
>        if (event && event->eventfd && !IS_ERR(event->eventfd))
>                eventfd_ctx_put(event->eventfd);
>
> -       if (!IS_ERR(efile))
> +       if (!IS_ERR_OR_NULL(efile))
>                fput(efile);
>
>        kfree(event);
> --
> 1.6.5.7
>
>
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