In cgroup_attach_proc it is now sufficient to only check that
oldcgrp==newcgrp once. Now that we are using threadgroup_lock()
during the migrations, oldcgrp will not change.
Signed-off-by: Mandeep Singh Baines <msb@xxxxxxxxxxxx>
Cc: Tejun Heo <tj@xxxxxxxxxx>
Cc: Li Zefan <lizf@xxxxxxxxxxxxxx>
Cc: containers@xxxxxxxxxxxxxxxxxxxxxxxxxx
Cc: cgroups@xxxxxxxxxxxxxxx
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
Cc: Frederic Weisbecker <fweisbec@xxxxxxxxx>
Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Paul Menage <paul@xxxxxxxxxxxxxx>
---
kernel/cgroup.c | 17 ++++++-----------
1 files changed, 6 insertions(+), 11 deletions(-)
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 6649529..4668a3f 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -2069,7 +2069,7 @@ static int css_set_prefetch(struct cgroup *cgrp, struct css_set *cg,
*/
int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader)
{
- int retval, i, group_size, nr_migrating_tasks;
+ int retval, i, group_size;
struct cgroup_subsys *ss, *failed_ss = NULL;
/* guaranteed to be initialized later, but the compiler needs this */
struct css_set *oldcg;
@@ -2120,7 +2120,7 @@ int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader)
}
/* take a reference on each task in the group to go in the array. */
tsk = leader;
- i = nr_migrating_tasks = 0;
+ i = 0;
do {
struct task_and_cgroup ent;
@@ -2136,11 +2136,12 @@ int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader)
*/
ent.task = tsk;
ent.cgrp = task_cgroup_from_root(tsk, root);
+ /* nothing to do if this task is already in the cgroup */
+ if (ent.cgrp == cgrp)
+ continue;
retval = flex_array_put(group, i, &ent, GFP_ATOMIC);
BUG_ON(retval != 0);
i++;
- if (ent.cgrp != cgrp)
- nr_migrating_tasks++;
} while_each_thread(leader, tsk);
/* remember the number of threads in the array for later. */
group_size = i;
@@ -2150,7 +2151,7 @@ int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader)
/* methods shouldn't be called if no task is actually migrating */
retval = 0;
- if (!nr_migrating_tasks)
+ if (!group_size)
goto out_free_group_list;
/*
@@ -2173,9 +2174,6 @@ int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader)
INIT_LIST_HEAD(&newcg_list);
for (i = 0; i < group_size; i++) {
tc = flex_array_get(group, i);
- /* nothing to do if this task is already in the cgroup */
- if (tc->cgrp == cgrp)
- continue;
/* get old css_set pointer */
task_lock(tc->task);
oldcg = tc->task->cgroups;
@@ -2193,9 +2191,6 @@ int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader)
*/
for (i = 0; i < group_size; i++) {
tc = flex_array_get(group, i);
- /* leave current thread as it is if it's already there */
- if (tc->cgrp == cgrp)
- continue;
retval = cgroup_task_migrate(cgrp, tc->cgrp, tc->task, true);
BUG_ON(retval);
}
--
1.7.3.1
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