cpuset: make sure new tasks conform to the current config of the cpuset

commit 06f4e94898918bcad00cdd4d349313a439d6911e upstream.

A new task inherits cpus_allowed and mems_allowed masks from its parent,
but if someone changes cpuset's config by writing to cpuset.cpus/cpuset.mems
before this new task is inserted into the cgroup's task list, the new task
won't be updated accordingly.

Signed-off-by: Zefan Li <lizefan@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index 524a8eef2965574e9f080abb8fba6a4c646d8049..533494236c122b018e3c31c106640ff7a1831e39 100644 (file)
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -1963,6 +1963,20 @@ static void cpuset_css_free(struct cgroup_subsys_state *css)
        kfree(cs);
 }
 
+/*
+ * Make sure the new task conform to the current state of its parent,
+ * which could have been changed by cpuset just after it inherits the
+ * state from the parent and before it sits on the cgroup's task list.
+ */
+void cpuset_fork(struct task_struct *task)
+{
+       if (task_css_is_root(task, cpuset_cgrp_id))
+               return;
+
+       set_cpus_allowed_ptr(task, &current->cpus_allowed);
+       task->mems_allowed = current->mems_allowed;
+}
+
 struct cgroup_subsys cpuset_cgrp_subsys = {
        .css_alloc = cpuset_css_alloc,
        .css_online = cpuset_css_online,
@@ -1971,6 +1985,7 @@ struct cgroup_subsys cpuset_cgrp_subsys = {
        .can_attach = cpuset_can_attach,
        .cancel_attach = cpuset_cancel_attach,
        .attach = cpuset_attach,
+       .fork           = cpuset_fork,
        .base_cftypes = files,
        .early_init = 1,
 };