// SPDX-License-Identifier: GPL-2.0-only/* * Process number limiting controller for cgroups. * * Used to allow a cgroup hierarchy to stop any new processes from fork()ing * after a certain limit is reached. * * Since it is trivial to hit the task limit without hitting any kmemcg limits * in place, PIDs are a fundamental resource. As such, PID exhaustion must be * preventable in the scope of a cgroup hierarchy by allowing resource limiting * of the number of tasks in a cgroup. * * In order to use the `pids` controller, set the maximum number of tasks in * pids.max (this is not available in the root cgroup for obvious reasons). The * number of processes currently in the cgroup is given by pids.current. * Organisational operations are not blocked by cgroup policies, so it is * possible to have pids.current > pids.max. However, it is not possible to * violate a cgroup policy through fork(). fork() will return -EAGAIN if forking * would cause a cgroup policy to be violated. * * To set a cgroup to have no limit, set pids.max to "max". This is the default * for all new cgroups (N.B. that PID limits are hierarchical, so the most * stringent limit in the hierarchy is followed). * * pids.current tracks all child cgroup hierarchies, so parent/pids.current is * a superset of parent/child/pids.current. * * Copyright (C) 2015 Aleksa Sarai <cyphar@cyphar.com> */ #include <linux/kernel.h>#include <linux/threads.h>#include <linux/atomic.h>#include <linux/cgroup.h>#include <linux/slab.h>#include <linux/sched/task.h> #define PIDS_MAX (PID_MAX_LIMIT + 1ULL)#define PIDS_MAX_STR "max" enum pidcg_event { /* Fork failed in subtree because this pids_cgroup limit was hit. */ PIDCG_MAX, /* Fork failed in this pids_cgroup because ancestor limit was hit. */ PIDCG_FORKFAIL, NR_PIDCG_EVENTS,}; struct pids_cgroup { struct cgroup_subsys_state css; /* * Use 64-bit types so that we can safely represent "max" as * %PIDS_MAX = (%PID_MAX_LIMIT + 1). */ atomic64_t counter; atomic64_t limit; int64_t watermark; /* Handles for pids.events[.local] */ struct cgroup_file events_file; struct cgroup_file events_local_file; atomic64_t events[NR_PIDCG_EVENTS]; atomic64_t events_local[NR_PIDCG_EVENTS];}; static struct pids_cgroup *css_pids(struct cgroup_subsys_state *css){ return container_of(css, struct pids_cgroup, css);} static struct pids_cgroup *parent_pids(struct pids_cgroup *pids){ return css_pids(pids->css.parent);} static struct cgroup_subsys_state *pids_css_alloc(struct cgroup_subsys_state *parent){ struct pids_cgroup *pids; pids = kzalloc_obj(struct pids_cgroup); if (!pids) return ERR_PTR(-ENOMEM); atomic64_set(&pids->limit, PIDS_MAX); return &pids->css;} static void pids_css_free(struct cgroup_subsys_state *css){ kfree(css_pids(css));} static void pids_update_watermark(struct pids_cgroup *p, int64_t nr_pids){ /* * This is racy, but we don't need perfectly accurate tallying of * the watermark, and this lets us avoid extra atomic overhead. */ if (nr_pids > READ_ONCE(p->watermark)) WRITE_ONCE(p->watermark, nr_pids);} /** * pids_cancel - uncharge the local pid count * @pids: the pid cgroup state * @num: the number of pids to cancel * * This function will WARN if the pid count goes under 0, because such a case is * a bug in the pids controller proper. */static void pids_cancel(struct pids_cgroup *pids, int num){ /* * A negative count (or overflow for that matter) is invalid, * and indicates a bug in the `pids` controller proper. */ WARN_ON_ONCE(atomic64_add_negative(-num, &pids->counter));} /** * pids_uncharge - hierarchically uncharge the pid count * @pids: the pid cgroup state * @num: the number of pids to uncharge */static void pids_uncharge(struct pids_cgroup *pids, int num){ struct pids_cgroup *p; for (p = pids; parent_pids(p); p = parent_pids(p)) pids_cancel(p, num);} /** * pids_charge - hierarchically charge the pid count * @pids: the pid cgroup state * @num: the number of pids to charge * * This function does *not* follow the pid limit set. It cannot fail and the new * pid count may exceed the limit. This is only used for reverting failed * attaches, where there is no other way out than violating the limit. */static void pids_charge(struct pids_cgroup *pids, int num){ struct pids_cgroup *p; for (p = pids; parent_pids(p); p = parent_pids(p)) { int64_t new = atomic64_add_return(num, &p->counter); pids_update_watermark(p, new); }} /** * pids_try_charge - hierarchically try to charge the pid count * @pids: the pid cgroup state * @num: the number of pids to charge * @fail: storage of pid cgroup causing the fail * * This function follows the set limit. It will fail if the charge would cause * the new value to exceed the hierarchical limit. Returns 0 if the charge * succeeded, otherwise -EAGAIN. */static int pids_try_charge(struct pids_cgroup *pids, int num, struct pids_cgroup **fail){ struct pids_cgroup *p, *q; for (p = pids; parent_pids(p); p = parent_pids(p)) { int64_t new = atomic64_add_return(num, &p->counter); int64_t limit = atomic64_read(&p->limit); /* * Since new is capped to the maximum number of pid_t, if * p->limit is %PIDS_MAX then we know that this test will never * fail. */ if (new > limit) { *fail = p; goto revert; } /* * Not technically accurate if we go over limit somewhere up * the hierarchy, but that's tolerable for the watermark. */ pids_update_watermark(p, new); } return 0; revert: for (q = pids; q != p; q = parent_pids(q)) pids_cancel(q, num); pids_cancel(p, num); return -EAGAIN;} static int pids_can_attach(struct cgroup_taskset *tset){ struct task_struct *task; struct cgroup_subsys_state *dst_css; cgroup_taskset_for_each(task, dst_css, tset) { struct pids_cgroup *pids = css_pids(dst_css); struct cgroup_subsys_state *old_css; struct pids_cgroup *old_pids; /* * No need to pin @old_css between here and cancel_attach() * because cgroup core protects it from being freed before * the migration completes or fails. */ old_css = task_css(task, pids_cgrp_id); old_pids = css_pids(old_css); pids_charge(pids, 1); pids_uncharge(old_pids, 1); } return 0;} static void pids_cancel_attach(struct cgroup_taskset *tset){ struct task_struct *task; struct cgroup_subsys_state *dst_css; cgroup_taskset_for_each(task, dst_css, tset) { struct pids_cgroup *pids = css_pids(dst_css); struct cgroup_subsys_state *old_css; struct pids_cgroup *old_pids; old_css = task_css(task, pids_cgrp_id); old_pids = css_pids(old_css); pids_charge(old_pids, 1); pids_uncharge(pids, 1); }} static void pids_event(struct pids_cgroup *pids_forking, struct pids_cgroup *pids_over_limit){ struct pids_cgroup *p = pids_forking; /* Only log the first time limit is hit. */ if (atomic64_inc_return(&p->events_local[PIDCG_FORKFAIL]) == 1) { pr_info("cgroup: fork rejected by pids controller in "); pr_cont_cgroup_path(p->css.cgroup); pr_cont("\n"); } if (!cgroup_subsys_on_dfl(pids_cgrp_subsys) || cgrp_dfl_root.flags & CGRP_ROOT_PIDS_LOCAL_EVENTS) { cgroup_file_notify(&p->events_local_file); return; } atomic64_inc(&pids_over_limit->events_local[PIDCG_MAX]); cgroup_file_notify(&pids_over_limit->events_local_file); for (p = pids_over_limit; parent_pids(p); p = parent_pids(p)) { atomic64_inc(&p->events[PIDCG_MAX]); cgroup_file_notify(&p->events_file); }} /* * task_css_check(true) in pids_can_fork() and pids_cancel_fork() relies * on cgroup_threadgroup_change_begin() held by the copy_process(). */static int pids_can_fork(struct task_struct *task, struct css_set *cset){ struct pids_cgroup *pids, *pids_over_limit; int err; pids = css_pids(cset->subsys[pids_cgrp_id]); err = pids_try_charge(pids, 1, &pids_over_limit); if (err) pids_event(pids, pids_over_limit); return err;} static void pids_cancel_fork(struct task_struct *task, struct css_set *cset){ struct pids_cgroup *pids; pids = css_pids(cset->subsys[pids_cgrp_id]); pids_uncharge(pids, 1);} static void pids_release(struct task_struct *task){ struct pids_cgroup *pids = css_pids(task_css(task, pids_cgrp_id)); pids_uncharge(pids, 1);} static ssize_t pids_max_write(struct kernfs_open_file *of, char *buf, size_t nbytes, loff_t off){ struct cgroup_subsys_state *css = of_css(of); struct pids_cgroup *pids = css_pids(css); int64_t limit; int err; buf = strstrip(buf); if (!strcmp(buf, PIDS_MAX_STR)) { limit = PIDS_MAX; goto set_limit; } err = kstrtoll(buf, 0, &limit); if (err) return err; if (limit < 0 || limit >= PIDS_MAX) return -EINVAL; set_limit: /* * Limit updates don't need to be mutex'd, since it isn't * critical that any racing fork()s follow the new limit. */ atomic64_set(&pids->limit, limit); return nbytes;} static int pids_max_show(struct seq_file *sf, void *v){ struct cgroup_subsys_state *css = seq_css(sf); struct pids_cgroup *pids = css_pids(css); int64_t limit = atomic64_read(&pids->limit); if (limit >= PIDS_MAX) seq_printf(sf, "%s\n", PIDS_MAX_STR); else seq_printf(sf, "%lld\n", limit); return 0;} static s64 pids_current_read(struct cgroup_subsys_state *css, struct cftype *cft){ struct pids_cgroup *pids = css_pids(css); return atomic64_read(&pids->counter);} static s64 pids_peak_read(struct cgroup_subsys_state *css, struct cftype *cft){ struct pids_cgroup *pids = css_pids(css); return READ_ONCE(pids->watermark);} static int __pids_events_show(struct seq_file *sf, bool local){ struct pids_cgroup *pids = css_pids(seq_css(sf)); enum pidcg_event pe = PIDCG_MAX; atomic64_t *events; if (!cgroup_subsys_on_dfl(pids_cgrp_subsys) || cgrp_dfl_root.flags & CGRP_ROOT_PIDS_LOCAL_EVENTS) { pe = PIDCG_FORKFAIL; local = true; } events = local ? pids->events_local : pids->events; seq_printf(sf, "max %lld\n", (s64)atomic64_read(&events[pe])); return 0;} static int pids_events_show(struct seq_file *sf, void *v){ __pids_events_show(sf, false); return 0;} static int pids_events_local_show(struct seq_file *sf, void *v){ __pids_events_show(sf, true); return 0;} static struct cftype pids_files[] = { { .name = "max", .write = pids_max_write, .seq_show = pids_max_show, .flags = CFTYPE_NOT_ON_ROOT, }, { .name = "current", .read_s64 = pids_current_read, .flags = CFTYPE_NOT_ON_ROOT, }, { .name = "peak", .flags = CFTYPE_NOT_ON_ROOT, .read_s64 = pids_peak_read, }, { .name = "events", .seq_show = pids_events_show, .file_offset = offsetof(struct pids_cgroup, events_file), .flags = CFTYPE_NOT_ON_ROOT, }, { .name = "events.local", .seq_show = pids_events_local_show, .file_offset = offsetof(struct pids_cgroup, events_local_file), .flags = CFTYPE_NOT_ON_ROOT, }, { } /* terminate */}; static struct cftype pids_files_legacy[] = { { .name = "max", .write = pids_max_write, .seq_show = pids_max_show, .flags = CFTYPE_NOT_ON_ROOT, }, { .name = "current", .read_s64 = pids_current_read, .flags = CFTYPE_NOT_ON_ROOT, }, { .name = "peak", .flags = CFTYPE_NOT_ON_ROOT, .read_s64 = pids_peak_read, }, { .name = "events", .seq_show = pids_events_show, .file_offset = offsetof(struct pids_cgroup, events_file), .flags = CFTYPE_NOT_ON_ROOT, }, { } /* terminate */}; struct cgroup_subsys pids_cgrp_subsys = { .css_alloc = pids_css_alloc, .css_free = pids_css_free, .can_attach = pids_can_attach, .cancel_attach = pids_cancel_attach, .can_fork = pids_can_fork, .cancel_fork = pids_cancel_fork, .release = pids_release, .legacy_cftypes = pids_files_legacy, .dfl_cftypes = pids_files, .threaded = true,};
// SPDX-License-Identifier: GPL-2.0-only
/*
* Process number limiting controller for cgroups.
*
* Used to allow a cgroup hierarchy to stop any new processes from fork()ing
* after a certain limit is reached.
*
* Since it is trivial to hit the task limit without hitting any kmemcg limits
* in place, PIDs are a fundamental resource. As such, PID exhaustion must be
* preventable in the scope of a cgroup hierarchy by allowing resource limiting
* of the number of tasks in a cgroup.
*
* In order to use the `pids` controller, set the maximum number of tasks in
* pids.max (this is not available in the root cgroup for obvious reasons). The
* number of processes currently in the cgroup is given by pids.current.
* Organisational operations are not blocked by cgroup policies, so it is
* possible to have pids.current > pids.max. However, it is not possible to
* violate a cgroup policy through fork(). fork() will return -EAGAIN if forking
* would cause a cgroup policy to be violated.
*
* To set a cgroup to have no limit, set pids.max to "max". This is the default
* for all new cgroups (N.B. that PID limits are hierarchical, so the most
* stringent limit in the hierarchy is followed).
*
* pids.current tracks all child cgroup hierarchies, so parent/pids.current is
* a superset of parent/child/pids.current.
*
* Copyright (C) 2015 Aleksa Sarai <cyphar@cyphar.com>
*/
#include <linux/kernel.h>
#include <linux/threads.h>
#include <linux/atomic.h>
#include <linux/cgroup.h>
#include <linux/slab.h>
#include <linux/sched/task.h>
#define PIDS_MAX (PID_MAX_LIMIT + 1ULL)
#define PIDS_MAX_STR "max"
enum pidcg_event {
/* Fork failed in subtree because this pids_cgroup limit was hit. */
PIDCG_MAX,
/* Fork failed in this pids_cgroup because ancestor limit was hit. */
PIDCG_FORKFAIL,
NR_PIDCG_EVENTS,
};
struct pids_cgroup {
struct cgroup_subsys_state css;
/*
* Use 64-bit types so that we can safely represent "max" as
* %PIDS_MAX = (%PID_MAX_LIMIT + 1).
*/
atomic64_t counter;
atomic64_t limit;
int64_t watermark;
/* Handles for pids.events[.local] */
struct cgroup_file events_file;
struct cgroup_file events_local_file;
atomic64_t events[NR_PIDCG_EVENTS];
atomic64_t events_local[NR_PIDCG_EVENTS];
};
static struct pids_cgroup *css_pids(struct cgroup_subsys_state *css)
{
return container_of(css, struct pids_cgroup, css);
}
static struct pids_cgroup *parent_pids(struct pids_cgroup *pids)
{
return css_pids(pids->css.parent);
}
static struct cgroup_subsys_state *
pids_css_alloc(struct cgroup_subsys_state *parent)
{
struct pids_cgroup *pids;
pids = kzalloc_obj(struct pids_cgroup);
if (!pids)
return ERR_PTR(-ENOMEM);
atomic64_set(&pids->limit, PIDS_MAX);
return &pids->css;
}
static void pids_css_free(struct cgroup_subsys_state *css)
{
kfree(css_pids(css));
}
static void pids_update_watermark(struct pids_cgroup *p, int64_t nr_pids)
{
/*
* This is racy, but we don't need perfectly accurate tallying of
* the watermark, and this lets us avoid extra atomic overhead.
*/
if (nr_pids > READ_ONCE(p->watermark))
WRITE_ONCE(p->watermark, nr_pids);
}
/**
* pids_cancel - uncharge the local pid count
* @pids: the pid cgroup state
* @num: the number of pids to cancel
*
* This function will WARN if the pid count goes under 0, because such a case is
* a bug in the pids controller proper.
*/
static void pids_cancel(struct pids_cgroup *pids, int num)
{
/*
* A negative count (or overflow for that matter) is invalid,
* and indicates a bug in the `pids` controller proper.
*/
WARN_ON_ONCE(atomic64_add_negative(-num, &pids->counter));
}
/**
* pids_uncharge - hierarchically uncharge the pid count
* @pids: the pid cgroup state
* @num: the number of pids to uncharge
*/
static void pids_uncharge(struct pids_cgroup *pids, int num)
{
struct pids_cgroup *p;
for (p = pids; parent_pids(p); p = parent_pids(p))
pids_cancel(p, num);
}
/**
* pids_charge - hierarchically charge the pid count
* @pids: the pid cgroup state
* @num: the number of pids to charge
*
* This function does *not* follow the pid limit set. It cannot fail and the new
* pid count may exceed the limit. This is only used for reverting failed
* attaches, where there is no other way out than violating the limit.
*/
static void pids_charge(struct pids_cgroup *pids, int num)
{
struct pids_cgroup *p;
for (p = pids; parent_pids(p); p = parent_pids(p)) {
int64_t new = atomic64_add_return(num, &p->counter);
pids_update_watermark(p, new);
}
}
/**
* pids_try_charge - hierarchically try to charge the pid count
* @pids: the pid cgroup state
* @num: the number of pids to charge
* @fail: storage of pid cgroup causing the fail
*
* This function follows the set limit. It will fail if the charge would cause
* the new value to exceed the hierarchical limit. Returns 0 if the charge
* succeeded, otherwise -EAGAIN.
*/
static int pids_try_charge(struct pids_cgroup *pids, int num, struct pids_cgroup **fail)
{
struct pids_cgroup *p, *q;
for (p = pids; parent_pids(p); p = parent_pids(p)) {
int64_t new = atomic64_add_return(num, &p->counter);
int64_t limit = atomic64_read(&p->limit);
/*
* Since new is capped to the maximum number of pid_t, if
* p->limit is %PIDS_MAX then we know that this test will never
* fail.
*/
if (new > limit) {
*fail = p;
goto revert;
}
/*
* Not technically accurate if we go over limit somewhere up
* the hierarchy, but that's tolerable for the watermark.
*/
pids_update_watermark(p, new);
}
return 0;
revert:
for (q = pids; q != p; q = parent_pids(q))
pids_cancel(q, num);
pids_cancel(p, num);
return -EAGAIN;
}
static int pids_can_attach(struct cgroup_taskset *tset)
{
struct task_struct *task;
struct cgroup_subsys_state *dst_css;
cgroup_taskset_for_each(task, dst_css, tset) {
struct pids_cgroup *pids = css_pids(dst_css);
struct cgroup_subsys_state *old_css;
struct pids_cgroup *old_pids;
/*
* No need to pin @old_css between here and cancel_attach()
* because cgroup core protects it from being freed before
* the migration completes or fails.
*/
old_css = task_css(task, pids_cgrp_id);
old_pids = css_pids(old_css);
pids_charge(pids, 1);
pids_uncharge(old_pids, 1);
}
return 0;
}
static void pids_cancel_attach(struct cgroup_taskset *tset)
{
struct task_struct *task;
struct cgroup_subsys_state *dst_css;
cgroup_taskset_for_each(task, dst_css, tset) {
struct pids_cgroup *pids = css_pids(dst_css);
struct cgroup_subsys_state *old_css;
struct pids_cgroup *old_pids;
old_css = task_css(task, pids_cgrp_id);
old_pids = css_pids(old_css);
pids_charge(old_pids, 1);
pids_uncharge(pids, 1);
}
}
static void pids_event(struct pids_cgroup *pids_forking,
struct pids_cgroup *pids_over_limit)
{
struct pids_cgroup *p = pids_forking;
/* Only log the first time limit is hit. */
if (atomic64_inc_return(&p->events_local[PIDCG_FORKFAIL]) == 1) {
pr_info("cgroup: fork rejected by pids controller in ");
pr_cont_cgroup_path(p->css.cgroup);
pr_cont("\n");
}
if (!cgroup_subsys_on_dfl(pids_cgrp_subsys) ||
cgrp_dfl_root.flags & CGRP_ROOT_PIDS_LOCAL_EVENTS) {
cgroup_file_notify(&p->events_local_file);
return;
}
atomic64_inc(&pids_over_limit->events_local[PIDCG_MAX]);
cgroup_file_notify(&pids_over_limit->events_local_file);
for (p = pids_over_limit; parent_pids(p); p = parent_pids(p)) {
atomic64_inc(&p->events[PIDCG_MAX]);
cgroup_file_notify(&p->events_file);
}
}
/*
* task_css_check(true) in pids_can_fork() and pids_cancel_fork() relies
* on cgroup_threadgroup_change_begin() held by the copy_process().
*/
static int pids_can_fork(struct task_struct *task, struct css_set *cset)
{
struct pids_cgroup *pids, *pids_over_limit;
int err;
pids = css_pids(cset->subsys[pids_cgrp_id]);
err = pids_try_charge(pids, 1, &pids_over_limit);
if (err)
pids_event(pids, pids_over_limit);
return err;
}
static void pids_cancel_fork(struct task_struct *task, struct css_set *cset)
{
struct pids_cgroup *pids;
pids = css_pids(cset->subsys[pids_cgrp_id]);
pids_uncharge(pids, 1);
}
static void pids_release(struct task_struct *task)
{
struct pids_cgroup *pids = css_pids(task_css(task, pids_cgrp_id));
pids_uncharge(pids, 1);
}
static ssize_t pids_max_write(struct kernfs_open_file *of, char *buf,
size_t nbytes, loff_t off)
{
struct cgroup_subsys_state *css = of_css(of);
struct pids_cgroup *pids = css_pids(css);
int64_t limit;
int err;
buf = strstrip(buf);
if (!strcmp(buf, PIDS_MAX_STR)) {
limit = PIDS_MAX;
goto set_limit;
}
err = kstrtoll(buf, 0, &limit);
if (err)
return err;
if (limit < 0 || limit >= PIDS_MAX)
return -EINVAL;
set_limit:
/*
* Limit updates don't need to be mutex'd, since it isn't
* critical that any racing fork()s follow the new limit.
*/
atomic64_set(&pids->limit, limit);
return nbytes;
}
static int pids_max_show(struct seq_file *sf, void *v)
{
struct cgroup_subsys_state *css = seq_css(sf);
struct pids_cgroup *pids = css_pids(css);
int64_t limit = atomic64_read(&pids->limit);
if (limit >= PIDS_MAX)
seq_printf(sf, "%s\n", PIDS_MAX_STR);
else
seq_printf(sf, "%lld\n", limit);
return 0;
}
static s64 pids_current_read(struct cgroup_subsys_state *css,
struct cftype *cft)
{
struct pids_cgroup *pids = css_pids(css);
return atomic64_read(&pids->counter);
}
static s64 pids_peak_read(struct cgroup_subsys_state *css,
struct cftype *cft)
{
struct pids_cgroup *pids = css_pids(css);
return READ_ONCE(pids->watermark);
}
static int __pids_events_show(struct seq_file *sf, bool local)
{
struct pids_cgroup *pids = css_pids(seq_css(sf));
enum pidcg_event pe = PIDCG_MAX;
atomic64_t *events;
if (!cgroup_subsys_on_dfl(pids_cgrp_subsys) ||
cgrp_dfl_root.flags & CGRP_ROOT_PIDS_LOCAL_EVENTS) {
pe = PIDCG_FORKFAIL;
local = true;
}
events = local ? pids->events_local : pids->events;
seq_printf(sf, "max %lld\n", (s64)atomic64_read(&events[pe]));
return 0;
}
static int pids_events_show(struct seq_file *sf, void *v)
{
__pids_events_show(sf, false);
return 0;
}
static int pids_events_local_show(struct seq_file *sf, void *v)
{
__pids_events_show(sf, true);
return 0;
}
static struct cftype pids_files[] = {
{
.name = "max",
.write = pids_max_write,
.seq_show = pids_max_show,
.flags = CFTYPE_NOT_ON_ROOT,
},
{
.name = "current",
.read_s64 = pids_current_read,
.flags = CFTYPE_NOT_ON_ROOT,
},
{
.name = "peak",
.flags = CFTYPE_NOT_ON_ROOT,
.read_s64 = pids_peak_read,
},
{
.name = "events",
.seq_show = pids_events_show,
.file_offset = offsetof(struct pids_cgroup, events_file),
.flags = CFTYPE_NOT_ON_ROOT,
},
{
.name = "events.local",
.seq_show = pids_events_local_show,
.file_offset = offsetof(struct pids_cgroup, events_local_file),
.flags = CFTYPE_NOT_ON_ROOT,
},
{ } /* terminate */
};
static struct cftype pids_files_legacy[] = {
{
.name = "max",
.write = pids_max_write,
.seq_show = pids_max_show,
.flags = CFTYPE_NOT_ON_ROOT,
},
{
.name = "current",
.read_s64 = pids_current_read,
.flags = CFTYPE_NOT_ON_ROOT,
},
{
.name = "peak",
.flags = CFTYPE_NOT_ON_ROOT,
.read_s64 = pids_peak_read,
},
{
.name = "events",
.seq_show = pids_events_show,
.file_offset = offsetof(struct pids_cgroup, events_file),
.flags = CFTYPE_NOT_ON_ROOT,
},
{ } /* terminate */
};
struct cgroup_subsys pids_cgrp_subsys = {
.css_alloc = pids_css_alloc,
.css_free = pids_css_free,
.can_attach = pids_can_attach,
.cancel_attach = pids_cancel_attach,
.can_fork = pids_can_fork,
.cancel_fork = pids_cancel_fork,
.release = pids_release,
.legacy_cftypes = pids_files_legacy,
.dfl_cftypes = pids_files,
.threaded = true,
};