From: Waiman Long <longman@xxxxxxxxxx>
[ Upstream commit 42a11bf5c5436e91b040aeb04063be1710bb9f9c ]
By default, the clone(2) syscall spawn a child process into the same
cgroup as its parent. With the use of the CLONE_INTO_CGROUP flag
introduced by commit ef2c41cf38a7 ("clone3: allow spawning processes
into cgroups"), the child will be spawned into a different cgroup which
is somewhat similar to writing the child's tid into "cgroup.threads".
The current cpuset_fork() method does not properly handle the
CLONE_INTO_CGROUP case where the cpuset of the child may be different
from that of its parent. Update the cpuset_fork() method to treat the
CLONE_INTO_CGROUP case similar to cpuset_attach().
Since the newly cloned task has not been running yet, its actual
memory usage isn't known. So it is not necessary to make change to mm
in cpuset_fork().
Fixes: ef2c41cf38a7 ("clone3: allow spawning processes into cgroups")
Reported-by: Giuseppe Scrivano <gscrivan@xxxxxxxxxx>
Signed-off-by: Waiman Long <longman@xxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx # v5.7+
Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
kernel/cgroup/cpuset.c | 62 ++++++++++++++++++++++++++++--------------
1 file changed, 42 insertions(+), 20 deletions(-)
diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index 3d254498eb275..a6829e21b50c3 100644
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -2242,16 +2242,33 @@ static void cpuset_cancel_attach(struct cgroup_taskset *tset)
}
/*
- * Protected by cpuset_rwsem. cpus_attach is used only by cpuset_attach()
+ * Protected by cpuset_rwsem. cpus_attach is used only by cpuset_attach_task()
* but we can't allocate it dynamically there. Define it global and
* allocate from cpuset_init().
*/
static cpumask_var_t cpus_attach;
+static nodemask_t cpuset_attach_nodemask_to;
+
+static void cpuset_attach_task(struct cpuset *cs, struct task_struct *task)
+{
+ percpu_rwsem_assert_held(&cpuset_rwsem);
+
+ if (cs != &top_cpuset)
+ guarantee_online_cpus(task, cpus_attach);
+ else
+ cpumask_copy(cpus_attach, task_cpu_possible_mask(task));
+ /*
+ * can_attach beforehand should guarantee that this doesn't
+ * fail. TODO: have a better way to handle failure here
+ */
+ WARN_ON_ONCE(set_cpus_allowed_ptr(task, cpus_attach));
+
+ cpuset_change_task_nodemask(task, &cpuset_attach_nodemask_to);
+ cpuset_update_task_spread_flags(cs, task);
+}
static void cpuset_attach(struct cgroup_taskset *tset)
{
- /* static buf protected by cpuset_rwsem */
- static nodemask_t cpuset_attach_nodemask_to;
struct task_struct *task;
struct task_struct *leader;
struct cgroup_subsys_state *css;
@@ -2266,20 +2283,8 @@ static void cpuset_attach(struct cgroup_taskset *tset)
guarantee_online_mems(cs, &cpuset_attach_nodemask_to);
- cgroup_taskset_for_each(task, css, tset) {
- if (cs != &top_cpuset)
- guarantee_online_cpus(task, cpus_attach);
- else
- cpumask_copy(cpus_attach, task_cpu_possible_mask(task));
- /*
- * can_attach beforehand should guarantee that this doesn't
- * fail. TODO: have a better way to handle failure here
- */
- WARN_ON_ONCE(set_cpus_allowed_ptr(task, cpus_attach));
-
- cpuset_change_task_nodemask(task, &cpuset_attach_nodemask_to);
- cpuset_update_task_spread_flags(cs, task);
- }
+ cgroup_taskset_for_each(task, css, tset)
+ cpuset_attach_task(cs, task);
/*
* Change mm for all threadgroup leaders. This is expensive and may
@@ -2952,11 +2957,28 @@ static void cpuset_bind(struct cgroup_subsys_state *root_css)
*/
static void cpuset_fork(struct task_struct *task)
{
- if (task_css_is_root(task, cpuset_cgrp_id))
+ struct cpuset *cs;
+ bool same_cs;
+
+ rcu_read_lock();
+ cs = task_cs(task);
+ same_cs = (cs == task_cs(current));
+ rcu_read_unlock();
+
+ if (same_cs) {
+ if (cs == &top_cpuset)
+ return;
+
+ set_cpus_allowed_ptr(task, current->cpus_ptr);
+ task->mems_allowed = current->mems_allowed;
return;
+ }
- set_cpus_allowed_ptr(task, current->cpus_ptr);
- task->mems_allowed = current->mems_allowed;
+ /* CLONE_INTO_CGROUP */
+ percpu_down_write(&cpuset_rwsem);
+ guarantee_online_mems(cs, &cpuset_attach_nodemask_to);
+ cpuset_attach_task(cs, task);
+ percpu_up_write(&cpuset_rwsem);
}
struct cgroup_subsys cpuset_cgrp_subsys = {
--
2.39.2
