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cgroup: cosmetic updates to cgroup_attach_task()

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cgroup_attach_task() is planned to go through restructuring.  Let's
tidy it up a bit in preparation.

* Update cgroup_attach_task() to receive the target task argument in
  @leader instead of @tsk.

* Rename @tsk to @task.

* Rename @retval to @ret.

This is purely cosmetic.

v2: get_nr_threads() was using uninitialized @task instead of @leader.
    Fixed.  Reported by Dan Carpenter.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
This commit is contained in:
Tejun Heo
2014-02-13 06:58:43 -05:00
parent bc668c7519
commit 9db8de3722
1 changed files with 23 additions and 22 deletions
Download Patch File Download Diff File Expand all files Collapse all files

45
kernel/cgroup.c
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@@ -1728,20 +1728,20 @@ static void cgroup_task_migrate(struct cgroup *old_cgrp,
/** /**
* cgroup_attach_task - attach a task or a whole threadgroup to a cgroup * cgroup_attach_task - attach a task or a whole threadgroup to a cgroup
* @cgrp: the cgroup to attach to * @cgrp: the cgroup to attach to
* @tsk: the task or the leader of the threadgroup to be attached * @leader: the task or the leader of the threadgroup to be attached
* @threadgroup: attach the whole threadgroup? * @threadgroup: attach the whole threadgroup?
* *
* Call holding cgroup_mutex and the group_rwsem of the leader. Will take * Call holding cgroup_mutex and the group_rwsem of the leader. Will take
* task_lock of @tsk or each thread in the threadgroup individually in turn. * task_lock of @tsk or each thread in the threadgroup individually in turn.
*/ */
static int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk, static int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *leader,
bool threadgroup) bool threadgroup)
{ {
int retval, i, group_size; int ret, i, group_size;
struct cgroupfs_root *root = cgrp->root; struct cgroupfs_root *root = cgrp->root;
struct cgroup_subsys_state *css, *failed_css = NULL; struct cgroup_subsys_state *css, *failed_css = NULL;
/* threadgroup list cursor and array */ /* threadgroup list cursor and array */
struct task_struct *leader = tsk; struct task_struct *task;
struct task_and_cgroup *tc; struct task_and_cgroup *tc;
struct flex_array *group; struct flex_array *group;
struct cgroup_taskset tset = { }; struct cgroup_taskset tset = { };
@@ -1754,7 +1754,7 @@ static int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk,
* threads exit, this will just be an over-estimate. * threads exit, this will just be an over-estimate.
*/ */
if (threadgroup) if (threadgroup)
group_size = get_nr_threads(tsk); group_size = get_nr_threads(leader);
else else
group_size = 1; group_size = 1;
/* flex_array supports very large thread-groups better than kmalloc. */ /* flex_array supports very large thread-groups better than kmalloc. */
@@ -1762,8 +1762,8 @@ static int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk,
if (!group) if (!group)
return -ENOMEM; return -ENOMEM;
/* pre-allocate to guarantee space while iterating in rcu read-side. */ /* pre-allocate to guarantee space while iterating in rcu read-side. */
retval = flex_array_prealloc(group, 0, group_size, GFP_KERNEL); ret = flex_array_prealloc(group, 0, group_size, GFP_KERNEL);
if (retval) if (ret)
goto out_free_group_list; goto out_free_group_list;
i = 0; i = 0;
@@ -1774,17 +1774,18 @@ static int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk,
*/ */
down_read(&css_set_rwsem); down_read(&css_set_rwsem);
rcu_read_lock(); rcu_read_lock();
task = leader;
do { do {
struct task_and_cgroup ent; struct task_and_cgroup ent;
/* @tsk either already exited or can't exit until the end */ /* @task either already exited or can't exit until the end */
if (tsk->flags & PF_EXITING) if (task->flags & PF_EXITING)
goto next; goto next;
/* as per above, nr_threads may decrease, but not increase. */ /* as per above, nr_threads may decrease, but not increase. */
BUG_ON(i >= group_size); BUG_ON(i >= group_size);
ent.task = tsk; ent.task = task;
ent.cgrp = task_cgroup_from_root(tsk, root); ent.cgrp = task_cgroup_from_root(task, root);
/* nothing to do if this task is already in the cgroup */ /* nothing to do if this task is already in the cgroup */
if (ent.cgrp == cgrp) if (ent.cgrp == cgrp)
goto next; goto next;
@@ -1792,13 +1793,13 @@ static int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk,
* saying GFP_ATOMIC has no effect here because we did prealloc * saying GFP_ATOMIC has no effect here because we did prealloc
* earlier, but it's good form to communicate our expectations. * earlier, but it's good form to communicate our expectations.
*/ */
retval = flex_array_put(group, i, &ent, GFP_ATOMIC); ret = flex_array_put(group, i, &ent, GFP_ATOMIC);
BUG_ON(retval != 0); BUG_ON(ret != 0);
i++; i++;
next: next:
if (!threadgroup) if (!threadgroup)
break; break;
} while_each_thread(leader, tsk); } while_each_thread(leader, task);
rcu_read_unlock(); rcu_read_unlock();
up_read(&css_set_rwsem); up_read(&css_set_rwsem);
/* remember the number of threads in the array for later. */ /* remember the number of threads in the array for later. */
@@ -1807,7 +1808,7 @@ static int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk,
tset.tc_array_len = group_size; tset.tc_array_len = group_size;
/* methods shouldn't be called if no task is actually migrating */ /* methods shouldn't be called if no task is actually migrating */
retval = 0; ret = 0;
if (!group_size) if (!group_size)
goto out_free_group_list; goto out_free_group_list;
@@ -1816,8 +1817,8 @@ static int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk,
*/ */
for_each_css(css, i, cgrp) { for_each_css(css, i, cgrp) {
if (css->ss->can_attach) { if (css->ss->can_attach) {
retval = css->ss->can_attach(css, &tset); ret = css->ss->can_attach(css, &tset);
if (retval) { if (ret) {
failed_css = css; failed_css = css;
goto out_cancel_attach; goto out_cancel_attach;
} }
@@ -1835,7 +1836,7 @@ static int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk,
old_cset = task_css_set(tc->task); old_cset = task_css_set(tc->task);
tc->cset = find_css_set(old_cset, cgrp); tc->cset = find_css_set(old_cset, cgrp);
if (!tc->cset) { if (!tc->cset) {
retval = -ENOMEM; ret = -ENOMEM;
goto out_put_css_set_refs; goto out_put_css_set_refs;
} }
} }
@@ -1863,9 +1864,9 @@ static int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk,
/* /*
* step 5: success! and cleanup * step 5: success! and cleanup
*/ */
retval = 0; ret = 0;
out_put_css_set_refs: out_put_css_set_refs:
if (retval) { if (ret) {
for (i = 0; i < group_size; i++) { for (i = 0; i < group_size; i++) {
tc = flex_array_get(group, i); tc = flex_array_get(group, i);
if (!tc->cset) if (!tc->cset)
@@ -1874,7 +1875,7 @@ out_put_css_set_refs:
} }
} }
out_cancel_attach: out_cancel_attach:
if (retval) { if (ret) {
for_each_css(css, i, cgrp) { for_each_css(css, i, cgrp) {
if (css == failed_css) if (css == failed_css)
break; break;
@@ -1884,7 +1885,7 @@ out_cancel_attach:
} }
out_free_group_list: out_free_group_list:
flex_array_free(group); flex_array_free(group);
return retval; return ret;
} }
/* /*