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cgroup/cpuset: Make cpuset_fork() handle CLONE_INTO_CGROUP properly

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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 ef2c41cf38 ("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: ef2c41cf38 ("clone3: allow spawning processes into cgroups")
Reported-by: Giuseppe Scrivano <gscrivan@redhat.com>
Signed-off-by: Waiman Long <longman@redhat.com>
Cc: stable@vger.kernel.org # v5.7+
Signed-off-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
Waiman Long 2023-04-11 09:35:58 -04:00 • committed by Tejun Heo
parent ba9182a896
commit 42a11bf5c5
1 changed files with 43 additions and 21 deletions
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64
kernel/cgroup/cpuset.c
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@ -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 * but we can't allocate it dynamically there. Define it global and
* allocate from cpuset_init(). * allocate from cpuset_init().
*/ */
static cpumask_var_t cpus_attach; 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 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 *task;
struct task_struct *leader; struct task_struct *leader;
struct cgroup_subsys_state *css; 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); guarantee_online_mems(cs, &cpuset_attach_nodemask_to);
cgroup_taskset_for_each(task, css, tset) { cgroup_taskset_for_each(task, css, tset)
if (cs != &top_cpuset) cpuset_attach_task(cs, task);
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);
}
/* /*
* Change mm for all threadgroup leaders. This is expensive and may * 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) static void cpuset_fork(struct task_struct *task)
{ {
if (task_css_is_root(task, cpuset_cgrp_id)) struct cpuset *cs;
return; bool same_cs;
set_cpus_allowed_ptr(task, current->cpus_ptr); rcu_read_lock();
task->mems_allowed = current->mems_allowed; 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 = { struct cgroup_subsys cpuset_cgrp_subsys = {