Commit 42a11bf5 authored by Waiman Long's avatar Waiman Long Committed by Tejun Heo
Browse files

cgroup/cpuset: Make cpuset_fork() handle CLONE_INTO_CGROUP properly 



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 ef2c41cf ("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: ef2c41cf ("clone3: allow spawning processes into cgroups")
Reported-by: default avatarGiuseppe Scrivano <gscrivan@redhat.com>
Signed-off-by: default avatarWaiman Long <longman@redhat.com>
Cc: stable@vger.kernel.org # v5.7+
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
parent ba9182a8

kernel/cgroup/cpuset.c

+42 −20
Original line number Diff line number Diff line
@@ -2515,16 +2515,33 @@ 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;
@@ -2555,20 +2572,8 @@ 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
@@ -3266,11 +3271,28 @@ 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;

	}



	/* 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 = {