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cgroups: add lock for child->cgroups in cgroup_post_fork()

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When cgroup_post_fork() is called, child is seen by find_task_by_vpid(),
so child->cgroups maybe be changed, It'll incorrect.

child->cgroups<old>'s refcnt is decreased
child->cgroups<new>'s refcnt is increased
but child->cg_list is added to child->cgroups<old>'s list.

Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Reviewed-by: Paul Menage <menage@google.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Pavel Emelyanov <xemul@openvz.org>
Cc: Balbir Singh <balbir@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Lai Jiangshan 2009-01-07 18:07:36 -08:00 committed by Linus Torvalds
parent c9d5409f8d
commit b12b533fa5
1 changed files with 2 additions and 0 deletions
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2
kernel/cgroup.c
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@ -2792,8 +2792,10 @@ void cgroup_post_fork(struct task_struct *child)
{ {
if (use_task_css_set_links) { if (use_task_css_set_links) {
write_lock(&css_set_lock); write_lock(&css_set_lock);
task_lock(child);
if (list_empty(&child->cg_list)) if (list_empty(&child->cg_list))
list_add(&child->cg_list, &child->cgroups->tasks); list_add(&child->cg_list, &child->cgroups->tasks);
task_unlock(child);
write_unlock(&css_set_lock); write_unlock(&css_set_lock);
} }
} }