lkml.org 
[lkml]   [2011]   [Dec]   [20]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH v2] cgroup: remove redundate get/put of old css_set from migrate
    On Mon, Dec 19, 2011 at 10:44:34AM -0800, Mandeep Singh Baines wrote:
    > Changes in V2:
    > * Updated commit message as per Tejun's feedback:
    > * https://lkml.org/lkml/2011/12/19/289
    >
    > -- >8 -- (snip)
    >
    > We can now assume that the css_set reference held by the task
    > will not go away for an exiting task. PF_EXITING state can be
    > trusted throughout migration by checking it after locking
    > threadgroup.
    >
    > While at it, renamed css_set_check_fetched to css_set_fetched.
    > !css_set_fetched() seems to read better than
    > !css_set_check_fetched().
    >
    > This patch depends on:
    >
    > commit cd3d095275374220921fcf0d4e0c16584b26ddbc
    > Author: Tejun Heo <tj@kernel.org>
    > Date: Mon Dec 12 18:12:21 2011 -0800
    >
    > cgroup: always lock threadgroup during migration
    >
    > Signed-off-by: Mandeep Singh Baines <msb@chromium.org>
    > Cc: Tejun Heo <tj@kernel.org>
    > Cc: Li Zefan <lizf@cn.fujitsu.com>
    > Cc: containers@lists.linux-foundation.org
    > Cc: cgroups@vger.kernel.org
    > Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
    > Cc: Frederic Weisbecker <fweisbec@gmail.com>
    > Cc: Oleg Nesterov <oleg@redhat.com>
    > Cc: Andrew Morton <akpm@linux-foundation.org>
    > Cc: Paul Menage <paul@paulmenage.org>
    > ---
    > kernel/cgroup.c | 25 ++++++-------------------
    > 1 files changed, 6 insertions(+), 19 deletions(-)
    >
    > diff --git a/kernel/cgroup.c b/kernel/cgroup.c
    > index 1b3b841..eb95e32 100644
    > --- a/kernel/cgroup.c
    > +++ b/kernel/cgroup.c
    > @@ -1856,7 +1856,6 @@ static int cgroup_task_migrate(struct cgroup *cgrp, struct cgroup *oldcgrp,
    > */
    > task_lock(tsk);
    > oldcg = tsk->cgroups;
    > - get_css_set(oldcg);
    > task_unlock(tsk);
    >
    > /* locate or allocate a new css_set for this task. */
    > @@ -1872,12 +1871,9 @@ static int cgroup_task_migrate(struct cgroup *cgrp, struct cgroup *oldcgrp,
    > might_sleep();
    > /* find_css_set will give us newcg already referenced. */
    > newcg = find_css_set(oldcg, cgrp);
    > - if (!newcg) {
    > - put_css_set(oldcg);
    > + if (!newcg)
    > return -ENOMEM;
    > - }
    > }
    > - put_css_set(oldcg);
    >
    > /* @tsk can't exit as its threadgroup is locked */
    > task_lock(tsk);
    > @@ -2015,9 +2011,8 @@ struct cg_list_entry {
    > struct list_head links;
    > };
    >
    > -static bool css_set_check_fetched(struct cgroup *cgrp,
    > - struct task_struct *tsk, struct css_set *cg,
    > - struct list_head *newcg_list)
    > +static bool css_set_fetched(struct cgroup *cgrp, struct task_struct *tsk,
    > + struct css_set *cg, struct list_head *newcg_list)
    > {
    > struct css_set *newcg;
    > struct cg_list_entry *cg_entry;
    > @@ -2191,19 +2186,11 @@ int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader)
    > /* get old css_set pointer */
    > task_lock(tc->task);
    > oldcg = tc->task->cgroups;
    > - get_css_set(oldcg);
    > task_unlock(tc->task);
    > - /* see if the new one for us is already in the list? */
    > - if (css_set_check_fetched(cgrp, tc->task, oldcg, &newcg_list)) {
    > - /* was already there, nothing to do. */
    > - put_css_set(oldcg);
    > - } else {
    > - /* we don't already have it. get new one. */
    > - retval = css_set_prefetch(cgrp, oldcg, &newcg_list);
    > - put_css_set(oldcg);
    > - if (retval)
    > + /* if we don't already have it in the list get a new one */
    > + if (!css_set_fetched(cgrp, tc->task, oldcg, &newcg_list))
    > + if (css_set_prefetch(cgrp, oldcg, &newcg_list))

    Forgot to put the error value in retval?

    > goto out_list_teardown;
    > - }
    > }
    >
    > /*
    > --
    > 1.7.3.1
    >

    Thanks.


    \
     
     \ /
      Last update: 2011-12-20 19:47    [W:0.036 / U:29.548 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site