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Date: Tue, 4 Oct 2011 03:27:24 +0300
From: "Kirill A. Shutemov" <kirill@...temov.name>
To: Frederic Weisbecker <fweisbec@...il.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
LKML <linux-kernel@...r.kernel.org>,
Paul Menage <paul@...lmenage.org>,
Li Zefan <lizf@...fujitsu.com>,
Johannes Weiner <hannes@...xchg.org>,
Aditya Kali <adityakali@...gle.com>,
Oleg Nesterov <oleg@...hat.com>,
Kay Sievers <kay.sievers@...y.org>,
Tim Hockin <thockin@...kin.org>, Tejun Heo <tj@...nel.org>,
Containers <containers@...ts.linux-foundation.org>
Subject: Re: [PATCH 04/10] cgroups: New cancel_attach_task subsystem callback
On Mon, Oct 03, 2011 at 09:07:06PM +0200, Frederic Weisbecker wrote:
> To cancel a process attachment on a subsystem, we only call the
> cancel_attach() callback once on the leader but we have no
> way to cancel the attachment individually for each member of
> the process group.
>
> This is going to be needed for the max number of tasks susbystem
> that is coming.
>
> To prepare for this integration, call a new cancel_attach_task()
> callback on each task of the group until we reach the member that
> failed to attach.
>
> Signed-off-by: Frederic Weisbecker <fweisbec@...il.com>
> Acked-by: Paul Menage <paul@...lmenage.org>
Acked-by: Kirill A. Shutemov <kirill@...temov.name>
> Cc: Li Zefan <lizf@...fujitsu.com>
> Cc: Johannes Weiner <hannes@...xchg.org>
> Cc: Aditya Kali <adityakali@...gle.com>
> Cc: Oleg Nesterov <oleg@...hat.com>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Kay Sievers <kay.sievers@...y.org>
> Cc: Tim Hockin <thockin@...kin.org>
> Cc: Tejun Heo <tj@...nel.org>
> Cc: Kirill A. Shutemov <kirill@...temov.name>
> Cc: Containers <containers@...ts.linux-foundation.org>
> ---
> Documentation/cgroups/cgroups.txt | 7 +++++++
> include/linux/cgroup.h | 2 ++
> kernel/cgroup.c | 24 ++++++++++++++++++++----
> 3 files changed, 29 insertions(+), 4 deletions(-)
>
> diff --git a/Documentation/cgroups/cgroups.txt b/Documentation/cgroups/cgroups.txt
> index 0621e93..3bc1dc9 100644
> --- a/Documentation/cgroups/cgroups.txt
> +++ b/Documentation/cgroups/cgroups.txt
> @@ -623,6 +623,13 @@ function, so that the subsystem can implement a rollback. If not, not necessary.
> This will be called only about subsystems whose can_attach() operation have
> succeeded.
>
> +void cancel_attach_task(struct cgroup *cgrp, struct task_struct *tsk)
> +(cgroup_mutex held by caller)
> +
> +As cancel_attach, but for operations that must be cancelled once per
> +task that wanted to be attached. This typically revert the effect of
> +can_attach_task().
> +
> void pre_attach(struct cgroup *cgrp);
> (cgroup_mutex held by caller)
>
> diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
> index ed34eb8..b62cf5e 100644
> --- a/include/linux/cgroup.h
> +++ b/include/linux/cgroup.h
> @@ -472,6 +472,8 @@ struct cgroup_subsys {
> struct task_struct *tsk);
> void (*cancel_attach)(struct cgroup_subsys *ss, struct cgroup *cgrp,
> struct task_struct *tsk);
> + void (*cancel_attach_task)(struct cgroup *cgrp,
> + struct task_struct *tsk);
> void (*pre_attach)(struct cgroup *cgrp);
> void (*attach_task)(struct cgroup *cgrp, struct cgroup *old_cgrp,
> struct task_struct *tsk);
> diff --git a/kernel/cgroup.c b/kernel/cgroup.c
> index fafebdb..709baef 100644
> --- a/kernel/cgroup.c
> +++ b/kernel/cgroup.c
> @@ -1883,6 +1883,9 @@ out:
> * remaining subsystems.
> */
> break;
> +
> + if (ss->cancel_attach_task)
> + ss->cancel_attach_task(cgrp, tsk);
> if (ss->cancel_attach)
> ss->cancel_attach(ss, cgrp, tsk);
> }
> @@ -1992,7 +1995,7 @@ int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader)
> {
> int retval, i, group_size;
> struct cgroup_subsys *ss, *failed_ss = NULL;
> - bool cancel_failed_ss = false;
> + struct task_struct *failed_task = NULL;
> /* guaranteed to be initialized later, but the compiler needs this */
> struct cgroup *oldcgrp = NULL;
> struct css_set *oldcg;
> @@ -2081,7 +2084,7 @@ int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader)
> oldcgrp, tsk);
> if (retval) {
> failed_ss = ss;
> - cancel_failed_ss = true;
> + failed_task = tsk;
> goto out_cancel_attach;
> }
> }
> @@ -2146,8 +2149,11 @@ int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader)
> if (ss->attach_task)
> ss->attach_task(cgrp, oldcgrp, tsk);
> }
> + } else if (retval == -ESRCH) {
> + if (ss->cancel_attach_task)
> + ss->cancel_attach_task(cgrp, tsk);
> } else {
> - BUG_ON(retval != -ESRCH);
> + BUG_ON(1);
> }
> }
> /* nothing is sensitive to fork() after this point. */
> @@ -2179,8 +2185,18 @@ out_cancel_attach:
> /* same deal as in cgroup_attach_task */
> if (retval) {
> for_each_subsys(root, ss) {
> + if (ss->cancel_attach_task && (ss != failed_ss ||
> + failed_task)) {
> + for (i = 0; i < group_size; i++) {
> + tsk = flex_array_get_ptr(group, i);
> + if (tsk == failed_task)
> + break;
> + ss->cancel_attach_task(cgrp, tsk);
> + }
> + }
> +
> if (ss == failed_ss) {
> - if (cancel_failed_ss && ss->cancel_attach)
> + if (failed_task && ss->cancel_attach)
> ss->cancel_attach(ss, cgrp, leader);
> break;
> }
> --
> 1.7.5.4
>
--
Kirill A. Shutemov
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