From 778968c55cc5688f87732f22656712770e5a9528 Mon Sep 17 00:00:00 2001 From: Frederic Weisbecker Date: Wed, 21 Dec 2011 20:03:19 +0100 Subject: [PATCH] --- yaml --- r: 281473 b: refs/heads/master c: 7e381b0eb1e1a9805c37335562e8dc02e7d7848c h: refs/heads/master i: 281471: 65524a515855477c7066cc42d7669847c50c9f49 v: v3 --- [refs] | 2 +- trunk/kernel/cgroup.c | 23 +++++++++++++++++------ 2 files changed, 18 insertions(+), 7 deletions(-) diff --git a/[refs] b/[refs] index 8c384cccd612..8c74f142c600 100644 --- a/[refs] +++ b/[refs] @@ -1,2 +1,2 @@ --- -refs/heads/master: 29e21368b9baf9c4b25060d65062da2dda926c70 +refs/heads/master: 7e381b0eb1e1a9805c37335562e8dc02e7d7848c diff --git a/trunk/kernel/cgroup.c b/trunk/kernel/cgroup.c index bc3caff138d8..dae50d0d8e4b 100644 --- a/trunk/kernel/cgroup.c +++ b/trunk/kernel/cgroup.c @@ -4556,20 +4556,31 @@ static const struct file_operations proc_cgroupstats_operations = { * * A pointer to the shared css_set was automatically copied in * fork.c by dup_task_struct(). However, we ignore that copy, since - * it was not made under the protection of RCU or cgroup_mutex, so - * might no longer be a valid cgroup pointer. cgroup_attach_task() might - * have already changed current->cgroups, allowing the previously - * referenced cgroup group to be removed and freed. + * it was not made under the protection of RCU, cgroup_mutex or + * threadgroup_change_begin(), so it might no longer be a valid + * cgroup pointer. cgroup_attach_task() might have already changed + * current->cgroups, allowing the previously referenced cgroup + * group to be removed and freed. + * + * Outside the pointer validity we also need to process the css_set + * inheritance between threadgoup_change_begin() and + * threadgoup_change_end(), this way there is no leak in any process + * wide migration performed by cgroup_attach_proc() that could otherwise + * miss a thread because it is too early or too late in the fork stage. * * At the point that cgroup_fork() is called, 'current' is the parent * task, and the passed argument 'child' points to the child task. */ void cgroup_fork(struct task_struct *child) { - task_lock(current); + /* + * We don't need to task_lock() current because current->cgroups + * can't be changed concurrently here. The parent obviously hasn't + * exited and called cgroup_exit(), and we are synchronized against + * cgroup migration through threadgroup_change_begin(). + */ child->cgroups = current->cgroups; get_css_set(child->cgroups); - task_unlock(current); INIT_LIST_HEAD(&child->cg_list); }