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| author | Mandeep Singh Baines <msb@chromium.org> | 2011-12-21 20:18:35 -0800 |
|---|---|---|
| committer | Tejun Heo <tj@kernel.org> | 2011-12-22 07:32:57 -0800 |
| commit | 026085ef5ae07c3197f2baacc091ce067b86ed11 (patch) | |
| tree | 0497b6414f79efff5b1ba855ddae70a2d850a2b4 | |
| parent | c84cdf75ccb2845f690579e838f13f7e744e3d23 (diff) | |
| download | linux-026085ef5ae07c3197f2baacc091ce067b86ed11.tar.gz linux-026085ef5ae07c3197f2baacc091ce067b86ed11.tar.bz2 linux-026085ef5ae07c3197f2baacc091ce067b86ed11.zip | |
cgroup: remove redundant get/put of old css_set from migrate
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.
Changes in V4:
* https://lkml.org/lkml/2011/12/20/368 (Tejun Heo)
* Fix typo in commit message
* Undid the rename of css_set_check_fetched
* https://lkml.org/lkml/2011/12/20/427 (Li Zefan)
* Fix comment in cgroup_task_migrate()
Changes in V3:
* https://lkml.org/lkml/2011/12/20/255 (Frederic Weisbecker)
* Fixed to put error in retval
Changes in V2:
* https://lkml.org/lkml/2011/12/19/289 (Tejun Heo)
* Updated commit message
-tj: removed stale patch description about dropped function rename.
Signed-off-by: Mandeep Singh Baines <msb@chromium.org>
Acked-by: Li Zefan <lizf@cn.fujitsu.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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>
| -rw-r--r-- | kernel/cgroup.c | 28 |
1 files changed, 8 insertions, 20 deletions
diff --git a/kernel/cgroup.c b/kernel/cgroup.c index 4936d8886b4f..82288088f6a5 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -1850,14 +1850,12 @@ static int cgroup_task_migrate(struct cgroup *cgrp, struct cgroup *oldcgrp, struct css_set *newcg; /* - * get old css_set. We are synchronized through threadgroup_lock() - * against PF_EXITING setting such that we can't race against - * cgroup_exit() changing the css_set to init_css_set and dropping the - * old one. + * We are synchronized through threadgroup_lock() against PF_EXITING + * setting such that we can't race against cgroup_exit() changing the + * css_set to init_css_set and dropping the old one. */ WARN_ON_ONCE(tsk->flags & PF_EXITING); oldcg = tsk->cgroups; - get_css_set(oldcg); /* locate or allocate a new css_set for this task. */ if (guarantee) { @@ -1872,12 +1870,9 @@ 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); task_lock(tsk); rcu_assign_pointer(tsk->cgroups, newcg); @@ -2186,18 +2181,11 @@ int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader) * init_css_set. */ oldcg = tc->task->cgroups; - get_css_set(oldcg); - /* 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_check_fetched(cgrp, tc->task, oldcg, &newcg_list)) + if (retval = css_set_prefetch(cgrp, oldcg, &newcg_list)) goto out_list_teardown; - } } /* |