// SPDX-License-Identifier: GPL-2.0-only
/*
* kernel/sched/syscalls.c
*
* Core kernel scheduler syscalls related code
*
* Copyright (C) 1991-2002 Linus Torvalds
* Copyright (C) 1998-2024 Ingo Molnar, Red Hat
*/
#include <linux/sched.h>
#include <linux/cpuset.h>
#include <linux/sched/debug.h>
#include <uapi/linux/sched/types.h>
#include "sched.h"
#include "autogroup.h"
static inline int __normal_prio(int policy, int rt_prio, int nice)
{
int prio;
if (dl_policy(policy))
prio = MAX_DL_PRIO - 1;
else if (rt_policy(policy))
prio = MAX_RT_PRIO - 1 - rt_prio;
else
prio = NICE_TO_PRIO(nice);
return prio;
}
/*
* Calculate the expected normal priority: i.e. priority
* without taking RT-inheritance into account. Might be
* boosted by interactivity modifiers. Changes upon fork,
* setprio syscalls, and whenever the interactivity
* estimator recalculates.
*/
static inline int normal_prio(struct task_struct *p)
{
return __normal_prio(p->policy, p->rt_priority, PRIO_TO_NICE(p->static_prio));
}
/*
* Calculate the current priority, i.e. the priority
* taken into account by the scheduler. This value might
* be boosted by RT tasks, or might be boosted by
* interactivity modifiers. Will be RT if the task got
* RT-boosted. If not then it returns p->normal_prio.
*/
static int effective_prio(struct task_struct *p)
{
p->normal_prio = normal_prio(p);
/*
* If we are RT tasks or we were boosted to RT priority,
* keep the priority unchanged. Otherwise, update priority
* to the normal priority:
*/
if (!rt_or_dl_prio(p->prio))
return p->normal_prio;
return p->prio;
}
void set_user_nice(struct task_struct *p, long nice)
{
bool queued, running;
struct rq *rq;
int old_prio;
if (task_nice(p) == nice || nice < MIN_NICE || nice > MAX_NICE)
return;
/*
* We have to be careful, if called from sys_setpriority(),
* the task might be in the middle of scheduling on another CPU.
*/
CLASS(task_rq_lock, rq_guard)(p);
rq = rq_guard.rq;
update_rq_clock(rq);
/*
* The RT priorities are set via sched_setscheduler(), but we still
* allow the 'normal' nice value to be set - but as expected
* it won't have any effect on scheduling until the task is
* SCHED_DEADLINE, SCHED_FIFO or SCHED_RR:
*/
if (task_has_dl_policy(p) || task_has_rt_policy(p)) {
p->static_prio = NICE_TO_PRIO(nice);
return;
}
queued = task_on_rq_queued(p);
running = task_current(rq, p);
if (queued)
dequeue_task(rq, p, DEQUEUE_SAVE | DEQUEUE_NOCLOCK);
if (running)
put_prev_task(rq, p);
p->static_prio = NICE_TO_PRIO(nice);
set_load_weight(p, true);
old_prio = p->prio;
p->prio = effective_prio(p);
if (queued)
enqueue_task(rq, p, ENQUEUE_RESTORE | ENQUEUE_NOCLOCK);
if (running)
set_next_task(rq, p);
/*
* If the task increased its priority or is running and
* lowered its priority, then reschedule its CPU:
*/
p->sched_class->prio_changed(rq, p, old_prio);
}
EXPORT_SYMBOL(set_user_nice);
/*
* is_nice_reduction - check if nice value is an actual reduction
*
* Similar to can_nice() but does not perform a capability check.
*
* @p: task
* @nice: nice value
*/
static bool is_nice_reduction(const struct task_struct *p, const int nice)
{
/* Convert nice value [19,-20] to rlimit style value [1,40]: */
int nice_rlim = nice_to_rlimit(nice);
return (nice_rlim <= task_rlimit(p, RLIMIT_NICE));
}
/*
* can_nice - check if a task can reduce its nice value
* @p: task
* @nice: nice value
*/
int can_nice(const struct task_struct *p, const int nice)
{
return is_nice_reduction(p, nice) || capable(CAP_SYS_NICE);
}
#ifdef __ARCH_WANT_SYS_NICE
/*
* sys_nice - change the priority of the current process.
* @increment: priority increment
*
* sys_setpriority is a more generic, but much slower function that
* does similar things.
*/
SYSCALL_DEFINE1(nice, int, increment)
{
long nice, retval;
/*
* Setpriority might change our priority at the same moment.
* We don't have to worry. Conceptually one call occurs first
* and we have a single winner.
*/
increment = clamp(increment, -NICE_WIDTH, NICE_WIDTH);
nice = task_nice(current) + increment;
nice = clamp_val(nice, MIN_NICE, MAX_NICE);
if (increment < 0 && !can_nice(current, nice))
return -EPERM;
retval = security_task_setnice(current, nice);
if (retval)
return retval;
set_user_nice(current, nice);
return 0;
}
#endif
/**
* task_prio - return the priority value of a given task.
* @p: the task in question.
*
* Return: The priority value as seen by users in /proc.
*
* sched policy return value kernel prio user prio/nice
*
* normal, batch, idle [0 ... 39] [100 ... 139] 0/[-20 ... 19]
* fifo, rr [-2 ... -100] [98 ... 0] [1 ... 99]
* deadline -101 -1 0
*/
int task_prio(const struct task_struct *p)
{
return p->prio - MAX_RT_PRIO;
}
/**
* idle_cpu - is a given CPU idle currently?
* @cpu: the processor in question.
*
* Return: 1 if the CPU is currently idle. 0 otherwise.
*/
int idle_cpu(int cpu)
{
struct rq *rq = cpu_rq(cpu);
if (rq->curr != rq->idle)
return 0;
if (rq->nr_running)
return 0;
#ifdef CONFIG_SMP
if (rq->ttwu_pending)
return 0;
#endif
return 1;
}
/**
* available_idle_cpu - is a given CPU idle for enqueuing work.
* @cpu: the CPU in question.
*
* Return: 1 if the CPU is currently idle. 0 otherwise.
*/
int available_idle_cpu(int cpu)
{
if (!idle_cpu(cpu))
return 0;
if (vcpu_is_preempted(cpu))
return 0;
return 1;
}
/**
* idle_task - return the idle task for a given CPU.
* @cpu: the processor in question.
*
* Return: The idle task for the CPU @cpu.
*/
struct task_struct *idle_task(int cpu)
{
return cpu_rq(cpu)->idle;
}
#ifdef CONFIG_SCHED_CORE
int sched_core_idle_cpu(int cpu)
{
struct rq *rq = cpu_rq(cpu);
if (sched_core_enabled(rq) && rq->curr == rq->idle)
return 1;
return idle_cpu(cpu);
}
#endif
/**
* find_process_by_pid - find a process with a matching PID value.
* @pid: the pid in question.
*
* The task of @pid, if found. %NULL otherwise.
*/
static struct task_struct *find_process_by_pid(pid_t pid)
{
return pid ? find_task_by_vpid(pid) : current;
}
static struct task_struct *find_get_task(pid_t pid)
{
struct task_struct *p;
guard(rcu)();
p = find_process_by_pid(pid);
if (likely(p))
get_task_struct(p);
return p;
}
DEFINE_CLASS(find_get_task, struct task_struct *, if (_T) put_task_struct(_T),
find_get_task(pid), pid_t pid)
/*
* sched_setparam() passes in -1 for its policy, to let the functions
* it calls know not to change it.
*/
#define SETPARAM_POLICY -1
static void __setscheduler_params(struct task_struct *p,
const struct sched_attr *attr)
{
int policy = attr->sched_policy;
if (policy == SETPARAM_POLICY)
policy = p->policy;
p->policy = policy;
if (dl_policy(policy)) {
__setparam_dl(p, attr);
} else if (fair_policy(policy)) {
p->static_prio = NICE_TO_PRIO(attr->sched_nice);
if (attr->sched_runtime) {
p->se.custom_slice = 1;
p->se.slice = clamp_t(u64, attr->sched_runtime,
NSEC_PER_MSEC/10, /* HZ=1000 * 10 */
NSEC_PER_MSEC*100); /* HZ=100 / 10 */
} else {
p->se.custom_slice = 0;
p->se.slice = sysctl_sched_base_slice;
}
}
/* rt-policy tasks do not have a timerslack */
if (rt_or_dl_task_policy(p)) {
p->timer_slack_ns = 0;
} else if (p->timer_slack_ns == 0) {
/* when switching back to non-rt policy, restore timerslack */
p->timer_slack_ns = p->default_timer_slack_ns;
}
/*
* __sched_setscheduler() ensures attr->sched_priority == 0 when
* !rt_policy. Always setting this ensures that things like
* getparam()/getattr() don't report silly values for !rt tasks.
*/
p->rt_priority = attr->sched_priority;
p->normal_prio = normal_prio(p);
set_load_weight(p, true);
}
/*
* Check the target process has a UID that matches the current process's:
*/
static bool check_same_owner(struct task_struct *p)
{
const struct cred *cred = current_cred(), *pcred;
guard(rcu)();
pcred = __task_cred(p);
return (uid_eq(cred->euid, pcred->euid) ||
uid_eq(cred->euid, pcred->uid));
}
#ifdef CONFIG_UCLAMP_TASK
static int uclamp_validate(struct task_struct *p,
const struct sched_attr *attr)
{
int util_min = p->uclamp_req[UCLAMP_MIN].value;
int util_max = p->uclamp_req[UCLAMP_MAX].value;
if (attr->sched_flags & SCHED_FLAG_UTIL_CLAMP_MIN) {
util_min = attr->sched_util_min;
if (util_min + 1 > SCHED_CAPACITY_SCALE + 1)
return -EINVAL;
}
if (attr->sched_flags & SCHED_FLAG_UTIL_CLAMP_MAX) {
util_max = attr->sched_util_max;
if (util_max + 1 > SCHED_CAPACITY_SCALE + 1)
return -EINVAL;
}
if (util_min != -1 && util_max != -1 && util_min > util_max)
return -EINVAL;
/*
* We have valid uclamp attributes; make sure uclamp is enabled.
*
* We need to do that here, because enabling static branches is a
* blocking operation which obviously cannot be done while holding
* scheduler locks.
*/
static_branch_enable(&sched_uclamp_used);
return 0;
}
static bool uclamp_reset(const struct sched_attr *attr,
enum uclamp_id clamp_id,
struct uclamp_se *uc_se)
{
/* Reset on sched class change for a non user-defined clamp value. */
if (likely(!(attr->sched_flags & SCHED_FLAG_UTIL_CLAMP)) &&
!uc_se->user_defined)
return true;
/* Reset on sched_util_{min,max} == -1. */
if (clamp_id == UCLAMP_MIN &&
attr->sched_flags & SCHED_FLAG_UTIL_CLAMP_MIN &&
attr->sched_util_min == -1) {
return true;
}
if (clamp_id == UCLAMP_MAX &&
attr->sched_flags & SCHED_FLAG_UTIL_CLAMP_MAX &&
attr->sched_util_max == -1) {
return true;
}
return false;
}
static void __setscheduler_uclamp(struct task_struct *p,
const struct sched_attr *attr)
{
enum uclamp_id clamp_id;
for_each_clamp_id(clamp_id) {
struct uclamp_se *uc_se = &p->uclamp_req[clamp_id];
unsigned int value;
if (!uclamp_reset(attr, clamp_id, uc_se))
continue;
/*
* RT by default have a 100% boost value that could be modified
* at runtime.
*/
if (unlikely(rt_task(p) && clamp_id == UCLAMP_MIN))
value = sysctl_sched_uclamp_util_min_rt_default;
else
value = uclamp_none(clamp_id);
uclamp_se_set(uc_se, value, false);
}
if (likely(!(attr->sched_flags & SCHED_FLAG_UTIL_CLAMP)))
return;
if (attr->sched_flags & SCHED_FLAG_UTIL_CLAMP_MIN &&
attr->sched_util_min != -1) {
uclamp_se_set(&p->uclamp_req[UCLAMP_MIN],
attr->sched_util_min, true);
}
if (attr->sched_flags & SCHED_FLAG_UTIL_CLAMP_MAX &&
attr->sched_util_max != -1) {
uclamp_se_set(&p->uclamp_req[UCLAMP_MAX],
attr->sched_util_max, true);
}
}
#else /* !CONFIG_UCLAMP_TASK: */
static inline int uclamp_validate(struct task_struct *p,
const struct sched_attr *attr)
{
return -EOPNOTSUPP;
}
static void __setscheduler_uclamp(struct task_struct *p,
const struct sched_attr *attr) { }
#endif
/*
* Allow unprivileged RT tasks to decrease priority.
* Only issue a capable test if needed and only once to avoid an audit
* event on permitted non-privileged operations:
*/
static int user_check_sched_setscheduler(struct task_struct *p,
const struct sched_attr *attr,
int policy, int reset_on_fork)
{
if (fair_policy(policy)) {
if (attr->sched_nice < task_nice(p) &&
!is_nice_reduction(p, attr->sched_nice))
goto req_priv;
}
if (rt_policy(policy)) {
unsigned long rlim_rtprio = task_rlimit(p, RLIMIT_RTPRIO);
/* Can't set/change the rt policy: */
if (policy != p->policy && !rlim_rtprio)
goto req_priv;
/* Can't increase priority: */
if (attr->sched_priority > p->rt_priority &&
attr->sched_priority > rlim_rtprio)
goto req_priv;
}
/*
* Can't set/change SCHED_DEADLINE policy at all for now
* (safest behavior); in the future we would like to allow
* unprivileged DL tasks to increase their relative deadline
* or reduce their runtime (both ways reducing utilization)
*/
if (dl_policy(policy))
goto req_priv;
/*
* Treat SCHED_IDLE as nice 20. Only allow a switch to
* SCHED_NORMAL if the RLIMIT_NICE would normally permit it.
*/
if (task_has_idle_policy(p) && !idle_policy(policy)) {
if (!is_nice_reduction(p, task_nice(p)))
goto req_priv;
}
/* Can't change other user's priorities: */
if (!check_same_owner(p))
goto req_priv;
/* Normal users shall not reset the sched_reset_on_fork flag: */
if (p->sched_reset_on_fork && !reset_on_fork)
goto req_priv;
return 0;
req_priv:
if (!capable(CAP_SYS_NICE))
return -EPERM;
return 0;
}
int __sched_setscheduler(struct task_struct *p,
const struct sched_attr *attr,
bool user, bool pi)
{
int oldpolicy = -1, policy = attr->sched_policy;
int retval, oldprio, newprio, queued, running;
const struct sched_class *prev_class;
struct balance_callback *head;
struct rq_flags rf;
int reset_on_fork;
int queue_flags = DEQUEUE_SAVE | DEQUEUE_MOVE | DEQUEUE_NOCLOCK;
struct rq *rq;
bool cpuset_locked = false;
/* The pi code expects interrupts enabled */
BUG_ON(pi && in_interrupt());
recheck:
/* Double check policy once rq lock held: */
if (policy < 0) {
reset_on_fork = p->sched_reset_on_fork;
policy = oldpolicy = p->policy;
} else {
reset_on_fork = !!(attr->sched_flags & SCHED_FLAG_RESET_ON_FORK);
if (!valid_policy(policy))
return -EINVAL;
}
if (attr->sched_flags & ~(SCHED_FLAG_ALL | SCHED_FLAG_SUGOV))
return -EINVAL;
/*
* Valid priorities for SCHED_FIFO and SCHED_RR are
* 1..MAX_RT_PRIO-1, valid priority for SCHED_NORMAL,
* SCHED_BATCH and SCHED_IDLE is 0.
*/
if (attr->sched_priority > MAX_RT_PRIO-1)
return -EINVAL;
if ((dl_policy(policy) && !__checkparam_dl(attr)) ||
(rt_policy(policy) != (attr->sched_priority != 0)))
return -EINVAL;
if (user) {
retval = user_check_sched_setscheduler(p, attr, policy, reset_on_fork);
if (retval)
return retval;
if (attr->sched_flags & SCHED_FLAG_SUGOV)
return -EINVAL;
retval = security_task_setscheduler(p);
if (retval)
return retval;
}
/* Update task specific "requested" clamps */
if (attr->sched_flags & SCHED_FLAG_UTIL_CLAMP) {
retval = uclamp_validate(p, attr);
if (retval)
return retval;
}
/*
* SCHED_DEADLINE bandwidth accounting relies on stable cpusets
* information.
*/
if (dl_policy(policy) || dl_policy(p->policy)) {
cpuset_locked = true;
cpuset_lock();
}
/*
* Make sure no PI-waiters arrive (or leave) while we are
* changing the priority of the task:
*
* To be able to change p->policy safely, the appropriate
* runqueue lock must be held.
*/
rq = task_rq_lock(p, &rf);
update_rq_clock(rq);
/*
* Changing the policy of the stop threads its a very bad idea:
*/
if (p == rq->stop) {
retval = -EINVAL;
goto unlock;
}
retval = scx_check_setscheduler(p, policy);
if (retval)
goto unlock;
/*
* If not changing anything there's no need to proceed further,
* but store a possible modification of reset_on_fork.
*/
if (unlikely(policy == p->policy)) {
if (fair_policy(policy) &&
(attr->sched_nice != task_nice(p) ||
(attr->sched_runtime != p->se.slice)))
goto change;
if (rt_policy(policy) && attr->sched_priority != p->rt_priority)
goto change;
if (dl_policy(policy) && dl_param_changed(p, attr))
goto change;
if (attr->sched_flags & SCHED_FLAG_UTIL_CLAMP)
goto change;
p->sched_reset_on_fork = reset_on_fork;
retval = 0;
goto unlock;
}
change:
if (user) {
#ifdef CONFIG_RT_GROUP_SCHED
/*
* Do not allow real-time tasks into groups that have no runtime
* assigned.
*/
if (rt_bandwidth_enabled() && rt_policy(policy) &&
task_group(p)->rt_bandwidth.rt_runtime == 0 &&
!task_group_is_autogroup(task_group(p))) {
retval = -EPERM;
goto unlock;
}
#endif
#ifdef CONFIG_SMP
if (dl_bandwidth_enabled() && dl_policy(policy) &&
!(attr->sched_flags & SCHED_FLAG_SUGOV)) {
cpumask_t *span = rq->rd->span;
/*
* Don't allow tasks with an affinity mask smaller than
* the entire root_domain to become SCHED_DEADLINE. We
* will also fail if there's no bandwidth available.
*/
if (!cpumask_subset(span, p->cpus_ptr) ||
rq->rd->dl_bw.bw == 0) {
retval = -EPERM;
goto unlock;
}
}
#endif
}
/* Re-check policy now with rq lock held: */
if (unlikely(oldpolicy != -1 && oldpolicy != p->policy)) {
policy = oldpolicy = -1;
task_rq_unlock(rq, p, &rf);
if (cpuset_locked)
cpuset_unlock();
goto recheck;
}
/*
* If setscheduling to SCHED_DEADLINE (or changing the parameters
* of a SCHED_DEADLINE task) we need to check if enough bandwidth
* is available.
*/
if ((dl_policy(policy) || dl_task(p)) && sched_dl_overflow(p, policy, attr)) {
retval = -EBUSY;
goto unlock;
}
p->sched_reset_on_fork = reset_on_fork;
oldprio = p->prio;
newprio = __normal_prio(policy, attr->sched_priority, attr->sched_nice);
if (pi) {
/*
* Take priority boosted tasks into account. If the new
* effective priority is unchanged, we just store the new
* normal parameters and do not touch the scheduler class and
* the runqueue. This will be done when the task deboost
* itself.
*/
newprio = rt_effective_prio(p, newprio);
if (newprio == oldprio)
queue_flags &= ~DEQUEUE_MOVE;
}
queued = task_on_rq_queued(p);
running = task_current(rq, p);
if (queued)
dequeue_task(rq, p, queue_flags);
if (running)
put_prev_task(rq, p);
prev_class = p->sched_class;
if (!(attr->sched_flags & SCHED_FLAG_KEEP_PARAMS)) {
__setscheduler_params(p, attr);
__setscheduler_prio(p, newprio);
}
__setscheduler_uclamp(p, attr);
check_class_changing(rq, p, prev_class);
if (queued) {
/*
* We enqueue to tail when the priority of a task is
* increased (user space view).
*/
if (oldprio < p->prio)
queue_flags |= ENQUEUE_HEAD;
enqueue_task(rq, p, queue_flags);
}
if (running)
set_next_task(rq, p);
check_class_changed(rq, p, prev_class, oldprio);
/* Avoid rq from going away on us: */
preempt_disable();
head = splice_balance_callbacks(rq);
task_rq_unlock(rq, p, &rf);
if (pi) {
if (cpuset_locked)
cpuset_unlock();
rt_mutex_adjust_pi(p);
}
/* Run balance callbacks after we've adjusted the PI chain: */
balance_callbacks(rq, head);
preempt_enable();
return 0;
unlock:
task_rq_unlock(rq, p, &rf);
if (cpuset_locked)
cpuset_unlock();
return retval;
}
static int _sched_setscheduler(struct task_struct *p, int policy,
const struct sched_param *param, bool check)
{
struct sched_attr attr = {
.sched_policy = policy,
.sched_priority = param->sched_priority,
.sched_nice = PRIO_TO_NICE(p->static_prio),
};
if (p->se.custom_slice)
attr.sched_runtime = p->se.slice;
/* Fixup the legacy SCHED_RESET_ON_FORK hack. */
if ((policy != SETPARAM_POLICY) && (policy & SCHED_RESET_ON_FORK)) {
attr.sched_flags |= SCHED_FLAG_RESET_ON_FORK;
policy &= ~SCHED_RESET_ON_FORK;
attr.sched_policy = policy;
}
return __sched_setscheduler(p, &attr, check, true);
}
/**
* sched_setscheduler - change the scheduling policy and/or RT priority of a thread.
* @p: the task in question.
* @policy: new policy.
* @param: structure containing the new RT priority.
*
* Use sched_set_fifo(), read its comment.
*
* Return: 0 on success. An error code otherwise.
*
* NOTE that the task may be already dead.
*/
int sched_setscheduler(struct task_struct *p, int policy,
const struct sched_param *param)
{
return _sched_setscheduler(p, policy, param, true);
}
int sched_setattr(struct task_struct *p, const struct sched_attr *attr)
{
return __sched_setscheduler(p, attr, true, true);
}
int sched_setattr_nocheck(struct task_struct *p, const struct sched_attr *attr)
{
return __sched_setscheduler(p, attr, false, true);
}
EXPORT_SYMBOL_GPL(sched_setattr_nocheck);
/**
* sched_setscheduler_nocheck - change the scheduling policy and/or RT priority of a thread from kernel-space.
* @p: the task in question.
* @policy: new policy.
* @param: structure containing the new RT priority.
*
* Just like sched_setscheduler, only don't bother checking if the
* current context has permission. For example, this is needed in
* stop_machine(): we create temporary high priority worker threads,
* but our caller might not have that capability.
*
* Return: 0 on success. An error code otherwise.
*/
int sched_setscheduler_nocheck(struct task_struct *p, int policy,
const struct sched_param *param)
{
return _sched_setscheduler(p, policy, param, false);
}
/*
* SCHED_FIFO is a broken scheduler model; that is, it is fundamentally
* incapable of resource management, which is the one thing an OS really should
* be doing.
*
* This is of course the reason it is limited to privileged users only.
*
* Worse still; it is fundamentally impossible to compose static priority
* workloads. You cannot take two correctly working static prio workloads
* and smash them together and still expect them to work.
*
* For this reason 'all' FIFO tasks the kernel creates are basically at:
*
* MAX_RT_PRIO / 2
*
* The administrator _MUST_ configure the system, the kernel simply doesn't
* know enough information to make a sensible choice.
*/
void sched_set_fifo(struct task_struct *p)
{
struct sched_param sp = { .sched_priority = MAX_RT_PRIO / 2 };
WARN_ON_ONCE(sched_setscheduler_nocheck(p, SCHED_FIFO, &sp) != 0);
}
EXPORT_SYMBOL_GPL(sched_set_fifo);
/*
* For when you don't much care about FIFO, but want to be above SCHED_NORMAL.
*/
void sched_set_fifo_low(struct task_struct *p)
{
struct sched_param sp = { .sched_priority = 1 };
WARN_ON_ONCE(sched_setscheduler_nocheck(p, SCHED_FIFO, &sp) != 0);
}
EXPORT_SYMBOL_GPL(sched_set_fifo_low);
void sched_set_normal(struct task_struct *p, int nice)
{
struct sched_attr attr = {
.sched_policy = SCHED_NORMAL,
.sched_nice = nice,
};
WARN_ON_ONCE(sched_setattr_nocheck(p, &attr) != 0);
}
EXPORT_SYMBOL_GPL(sched_set_normal);
static int
do_sched_setscheduler(pid_t pid, int policy, struct sched_param __user *param)
{
struct sched_param lparam;
if (!param || pid < 0)
return -EINVAL;
if (copy_from_user(&lparam, param, sizeof(struct sched_param)))
return -EFAULT;
CLASS(find_get_task, p)(pid);
if (!p)
return -ESRCH;
return sched_setscheduler(p, policy, &lparam);
}
/*
* Mimics kernel/events/core.c perf_copy_attr().
*/
static int sched_copy_attr(struct sched_attr __user *uattr, struct sched_attr *attr)
{
u32 size;
int ret;
/* Zero the full structure, so that a short copy will be nice: */
memset(attr, 0, sizeof(*attr));
ret = get_user(size, &uattr->size);
if (ret)
return ret;
/* ABI compatibility quirk: */
if (!size)
size = SCHED_ATTR_SIZE_VER0;
if (size < SCHED_ATTR_SIZE_VER0 || size > PAGE_SIZE)
goto err_size;
ret = copy_struct_from_user(attr, sizeof(*attr), uattr, size);
if (ret) {
if (ret == -E2BIG)
goto err_size;
return ret;
}
if ((attr->sched_flags & SCHED_FLAG_UTIL_CLAMP) &&
size < SCHED_ATTR_SIZE_VER1)
return -EINVAL;
/*
* XXX: Do we want to be lenient like existing syscalls; or do we want
* to be strict and return an error on out-of-bounds values?
*/
attr->sched_nice = clamp(attr->sched_nice, MIN_NICE, MAX_NICE);
return 0;
err_size:
put_user(sizeof(*attr), &uattr->size);
return -E2BIG;
}
static void get_params(struct task_struct *p, struct sched_attr *attr)
{
if (task_has_dl_policy(p)) {
__getparam_dl(p, attr);
} else if (task_has_rt_policy(p)) {
attr->sched_priority = p->rt_priority;
} else {
attr->sched_nice = task_nice(p);
attr->sched_runtime = p->se.slice;
}
}
/**
* sys_sched_setscheduler - set/change the scheduler policy and RT priority
* @pid: the pid in question.
* @policy: new policy.
* @param: structure containing the new RT priority.
*
* Return: 0 on success. An error code otherwise.
*/
SYSCALL_DEFINE3(sched_setscheduler, pid_t, pid, int, policy, struct sched_param __user *, param)
{
if (policy < 0)
return -EINVAL;
return do_sched_setscheduler(pid, policy, param);
}
/**
* sys_sched_setparam - set/change the RT priority of a thread
* @pid: the pid in question.
* @param: structure containing the new RT priority.
*
* Return: 0 on success. An error code otherwise.
*/
SYSCALL_DEFINE2(sched_setparam, pid_t, pid, struct sched_param __user *, param)
{
return do_sched_setscheduler(pid, SETPARAM_POLICY, param);
}
/**
* sys_sched_setattr - same as above, but with extended sched_attr
* @pid: the pid in question.
* @uattr: structure containing the extended parameters.
* @flags: for future extension.
*/
SYSCALL_DEFINE3(sched_setattr, pid_t, pid, struct sched_attr __user *, uattr,
unsigned int, flags)
{
struct sched_attr attr;
int retval;
if (!uattr || pid < 0 || flags)
return -EINVAL;
retval = sched_copy_attr(uattr, &attr);
if (retval)
return retval;
if ((int)attr.sched_policy < 0)
return -EINVAL;
if (attr.sched_flags & SCHED_FLAG_KEEP_POLICY)
attr.sched_policy = SETPARAM_POLICY;
CLASS(find_get_task, p)(pid);
if (!p)
return -ESRCH;
if (attr.sched_flags & SCHED_FLAG_KEEP_PARAMS)
get_params(p, &attr);
return sched_setattr(p, &attr);
}
/**
* sys_sched_getscheduler - get the policy (scheduling class) of a thread
* @pid: the pid in question.
*
* Return: On success, the policy of the thread. Otherwise, a negative error
* code.
*/
SYSCALL_DEFINE1(sched_getscheduler, pid_t, pid)
{
struct task_struct *p;
int retval;
if (pid < 0)
return -EINVAL;
guard(rcu)();
p = find_process_by_pid(pid);
if (!p)
return -ESRCH;
retval = security_task_getscheduler(p);
if (!retval) {
retval = p->policy;
if (p->sched_reset_on_fork)
retval |= SCHED_RESET_ON_FORK;
}
return retval;
}
/**
* sys_sched_getparam - get the RT priority of a thread
* @pid: the pid in question.
* @param: structure containing the RT priority.
*
* Return: On success, 0 and the RT priority is in @param. Otherwise, an error
* code.
*/
SYSCALL_DEFINE2(sched_getparam, pid_t, pid, struct sched_param __user *, param)
{
struct sched_param lp = { .sched_priority = 0 };
struct task_struct *p;
int retval;
if (!param || pid < 0)
return -EINVAL;
scoped_guard (rcu) {
p = find_process_by_pid(pid);
if (!p)
return -ESRCH;
retval = security_task_getscheduler(p);
if (retval)
return retval;
if (task_has_rt_policy(p))
lp.sched_priority = p->rt_priority;
}
/*
* This one might sleep, we cannot do it with a spinlock held ...
*/
return copy_to_user(param, &lp, sizeof(*param)) ? -EFAULT : 0;
}
/*
* Copy the kernel size attribute structure (which might be larger
* than what user-space knows about) to user-space.
*
* Note that all cases are valid: user-space buffer can be larger or
* smaller than the kernel-space buffer. The usual case is that both
* have the same size.
*/
static int
sched_attr_copy_to_user(struct sched_attr __user *uattr,
struct sched_attr *kattr,
unsigned int usize)
{
unsigned int ksize = sizeof(*kattr);
if (!access_ok(uattr, usize))
return -EFAULT;
/*
* sched_getattr() ABI forwards and backwards compatibility:
*
* If usize == ksize then we just copy everything to user-space and all is good.
*
* If usize < ksize then we only copy as much as user-space has space for,
* this keeps ABI compatibility as well. We skip the rest.
*
* If usize > ksize then user-space is using a newer version of the ABI,
* which part the kernel doesn't know about. Just ignore it - tooling can
* detect the kernel's knowledge of attributes from the attr->size value
* which is set to ksize in this case.
*/
kattr->size = min(usize, ksize);
if (copy_to_user(uattr, kattr, kattr->size))
return -EFAULT;
return 0;
}
/**
* sys_sched_getattr - similar to sched_getparam, but with sched_attr
* @pid: the pid in question.
* @uattr: structure containing the extended parameters.
* @usize: sizeof(attr) for fwd/bwd comp.
* @flags: for future extension.
*/
SYSCALL_DEFINE4(sched_getattr, pid_t, pid, struct sched_attr __user *, uattr,
unsigned int, usize, unsigned int, flags)
{
struct sched_attr kattr = { };
struct task_struct *p;
int retval;
if (!uattr || pid < 0 || usize > PAGE_SIZE ||
usize < SCHED_ATTR_SIZE_VER0 || flags)
return -EINVAL;
scoped_guard (rcu) {
p = find_process_by_pid(pid);
if (!p)
return -ESRCH;
retval = security_task_getscheduler(p);
if (retval)
return retval;
kattr.sched_policy = p->policy;
if (p->sched_reset_on_fork)
kattr.sched_flags |= SCHED_FLAG_RESET_ON_FORK;
get_params(p, &kattr);
kattr.sched_flags &= SCHED_FLAG_ALL;
#ifdef CONFIG_UCLAMP_TASK
/*
* This could race with another potential updater, but this is fine
* because it'll correctly read the old or the new value. We don't need
* to guarantee who wins the race as long as it doesn't return garbage.
*/
kattr.sched_util_min = p->uclamp_req[UCLAMP_MIN].value;
kattr.sched_util_max = p->uclamp_req[UCLAMP_MAX].value;
#endif
}
return sched_attr_copy_to_user(uattr, &kattr, usize);
}
#ifdef CONFIG_SMP
int dl_task_check_affinity(struct task_struct *p, const struct cpumask *mask)
{
/*
* If the task isn't a deadline task or admission control is
* disabled then we don't care about affinity changes.
*/
if (!task_has_dl_policy(p) || !dl_bandwidth_enabled())
return 0;
/*
* Since bandwidth control happens on root_domain basis,
* if admission test is enabled, we only admit -deadline
* tasks allowed to run on all the CPUs in the task's
* root_domain.
*/
guard(rcu)();
if (!cpumask_subset(task_rq(p)->rd->span, mask))
return -EBUSY;
return 0;
}
#endif /* CONFIG_SMP */
int __sched_setaffinity(struct task_struct *p, struct affinity_context *ctx)
{
int retval;
cpumask_var_t cpus_allowed, new_mask;
if (!alloc_cpumask_var(&cpus_allowed, GFP_KERNEL))
return -ENOMEM;
if (!alloc_cpumask_var(&new_mask, GFP_KERNEL)) {
retval = -ENOMEM;
goto out_free_cpus_allowed;
}
cpuset_cpus_allowed(p, cpus_allowed);
cpumask_and(new_mask, ctx->new_mask, cpus_allowed);
ctx->new_mask = new_mask;
ctx->flags |= SCA_CHECK;
retval = dl_task_check_affinity(p, new_mask);
if (retval)
goto out_free_new_mask;
retval = __set_cpus_allowed_ptr(p, ctx);
if (retval)
goto out_free_new_mask;
cpuset_cpus_allowed(p, cpus_allowed);
if (!cpumask_subset(new_mask, cpus_allowed)) {
/*
* We must have raced with a concurrent cpuset update.
* Just reset the cpumask to the cpuset's cpus_allowed.
*/
cpumask_copy(new_mask, cpus_allowed);
/*
* If SCA_USER is set, a 2nd call to __set_cpus_allowed_ptr()
* will restore the previous user_cpus_ptr value.
*
* In the unlikely event a previous user_cpus_ptr exists,
* we need to further restrict the mask to what is allowed
* by that old user_cpus_ptr.
*/
if (unlikely((ctx->flags & SCA_USER) && ctx->user_mask)) {
bool empty = !cpumask_and(new_mask, new_mask,
ctx->user_mask);
if (WARN_ON_ONCE(empty))
cpumask_copy(new_mask, cpus_allowed);
}
__set_cpus_allowed_ptr(p, ctx);
retval = -EINVAL;
}
out_free_new_mask:
free_cpumask_var(new_mask);
out_free_cpus_allowed:
free_cpumask_var(cpus_allowed);
return retval;
}
long sched_setaffinity(pid_t pid, const struct cpumask *in_mask)
{
struct affinity_context ac;
struct cpumask *user_mask;
int retval;
CLASS(find_get_task, p)(pid);
if (!p)
return -ESRCH;
if (p->flags & PF_NO_SETAFFINITY)
return -EINVAL;
if (!check_same_owner(p)) {
guard(rcu)();
if (!ns_capable(__task_cred(p)->user_ns, CAP_SYS_NICE))
return -EPERM;
}
retval = security_task_setscheduler(p);
if (retval)
return retval;
/*
* With non-SMP configs, user_cpus_ptr/user_mask isn't used and
* alloc_user_cpus_ptr() returns NULL.
*/
user_mask = alloc_user_cpus_ptr(NUMA_NO_NODE);
if (user_mask) {
cpumask_copy(user_mask, in_mask);
} else if (IS_ENABLED(CONFIG_SMP)) {
return -ENOMEM;
}
ac = (struct affinity_context){
.new_mask = in_mask,
.user_mask = user_mask,
.flags = SCA_USER,
};
retval = __sched_setaffinity(p, &ac);
kfree(ac.user_mask);
return retval;
}
static int get_user_cpu_mask(unsigned long __user *user_mask_ptr, unsigned len,
struct cpumask *new_mask)
{
if (len < cpumask_size())
cpumask_clear(new_mask);
else if (len > cpumask_size())
len = cpumask_size();
return copy_from_user(new_mask, user_mask_ptr, len) ? -EFAULT : 0;
}
/**
* sys_sched_setaffinity - set the CPU affinity of a process
* @pid: pid of the process
* @len: length in bytes of the bitmask pointed to by user_mask_ptr
* @user_mask_ptr: user-space pointer to the new CPU mask
*
* Return: 0 on success. An error code otherwise.
*/
SYSCALL_DEFINE3(sched_setaffinity, pid_t, pid, unsigned int, len,
unsigned long __user *, user_mask_ptr)
{
cpumask_var_t new_mask;
int retval;
if (!alloc_cpumask_var(&new_mask, GFP_KERNEL))
return -ENOMEM;
retval = get_user_cpu_mask(user_mask_ptr, len, new_mask);
if (retval == 0)
retval = sched_setaffinity(pid, new_mask);
free_cpumask_var(new_mask);
return retval;
}
long sched_getaffinity(pid_t pid, struct cpumask *mask)
{
struct task_struct *p;
int retval;
guard(rcu)();
p = find_process_by_pid(pid);
if (!p)
return -ESRCH;
retval = security_task_getscheduler(p);
if (retval)
return retval;
guard(raw_spinlock_irqsave)(&p->pi_lock);
cpumask_and(mask, &p->cpus_mask, cpu_active_mask);
return 0;
}
/**
* sys_sched_getaffinity - get the CPU affinity of a process
* @pid: pid of the process
* @len: length in bytes of the bitmask pointed to by user_mask_ptr
* @user_mask_ptr: user-space pointer to hold the current CPU mask
*
* Return: size of CPU mask copied to user_mask_ptr on success. An
* error code otherwise.
*/
SYSCALL_DEFINE3(sched_getaffinity, pid_t, pid, unsigned int, len,
unsigned long __user *, user_mask_ptr)
{
int ret;
cpumask_var_t mask;
if ((len * BITS_PER_BYTE) < nr_cpu_ids)
return -EINVAL;
if (len & (sizeof(unsigned long)-1))
return -EINVAL;
if (!zalloc_cpumask_var(&mask, GFP_KERNEL))
return -ENOMEM;
ret = sched_getaffinity(pid, mask);
if (ret == 0) {
unsigned int retlen = min(len, cpumask_size());
if (copy_to_user(user_mask_ptr, cpumask_bits(mask), retlen))
ret = -EFAULT;
else
ret = retlen;
}
free_cpumask_var(mask);
return ret;
}
static void do_sched_yield(void)
{
struct rq_flags rf;
struct rq *rq;
rq = this_rq_lock_irq(&rf);
schedstat_inc(rq->yld_count);
current->sched_class->yield_task(rq);
preempt_disable();
rq_unlock_irq(rq, &rf);
sched_preempt_enable_no_resched();
schedule();
}
/**
* sys_sched_yield - yield the current processor to other threads.
*
* This function yields the current CPU to other tasks. If there are no
* other threads running on this CPU then this function will return.
*
* Return: 0.
*/
SYSCALL_DEFINE0(sched_yield)
{
do_sched_yield();
return 0;
}
/**
* yield - yield the current processor to other threads.
*
* Do not ever use this function, there's a 99% chance you're doing it wrong.
*
* The scheduler is at all times free to pick the calling task as the most
* eligible task to run, if removing the yield() call from your code breaks
* it, it's already broken.
*
* Typical broken usage is:
*
* while (!event)
* yield();
*
* where one assumes that yield() will let 'the other' process run that will
* make event true. If the current task is a SCHED_FIFO task that will never
* happen. Never use yield() as a progress guarantee!!
*
* If you want to use yield() to wait for something, use wait_event().
* If you want to use yield() to be 'nice' for others, use cond_resched().
* If you still want to use yield(), do not!
*/
void __sched yield(void)
{
set_current_state(TASK_RUNNING);
do_sched_yield();
}
EXPORT_SYMBOL(yield);
/**
* yield_to - yield the current processor to another thread in
* your thread group, or accelerate that thread toward the
* processor it's on.
* @p: target task
* @preempt: whether task preemption is allowed or not
*
* It's the caller's job to ensure that the target task struct
* can't go away on us before we can do any checks.
*
* Return:
* true (>0) if we indeed boosted the target task.
* false (0) if we failed to boost the target.
* -ESRCH if there's no task to yield to.
*/
int __sched yield_to(struct task_struct *p, bool preempt)
{
struct task_struct *curr = current;
struct rq *rq, *p_rq;
int yielded = 0;
scoped_guard (irqsave) {
rq = this_rq();
again:
p_rq = task_rq(p);
/*
* If we're the only runnable task on the rq and target rq also
* has only one task, there's absolutely no point in yielding.
*/
if (rq->nr_running == 1 && p_rq->nr_running == 1)
return -ESRCH;
guard(double_rq_lock)(rq, p_rq);
if (task_rq(p) != p_rq)
goto again;
if (!curr->sched_class->yield_to_task)
return 0;
if (curr->sched_class != p->sched_class)
return 0;
if (task_on_cpu(p_rq, p) || !task_is_running(p))
return 0;
yielded = curr->sched_class->yield_to_task(rq, p);
if (yielded) {
schedstat_inc(rq->yld_count);
/*
* Make p's CPU reschedule; pick_next_entity
* takes care of fairness.
*/
if (preempt && rq != p_rq)
resched_curr(p_rq);
}
}
if (yielded)
schedule();
return yielded;
}
EXPORT_SYMBOL_GPL(yield_to);
/**
* sys_sched_get_priority_max - return maximum RT priority.
* @policy: scheduling class.
*
* Return: On success, this syscall returns the maximum
* rt_priority that can be used by a given scheduling class.
* On failure, a negative error code is returned.
*/
SYSCALL_DEFINE1(sched_get_priority_max, int, policy)
{
int ret = -EINVAL;
switch (policy) {
case SCHED_FIFO:
case SCHED_RR:
ret = MAX_RT_PRIO-1;
break;
case SCHED_DEADLINE:
case SCHED_NORMAL:
case SCHED_BATCH:
case SCHED_IDLE:
case SCHED_EXT:
ret = 0;
break;
}
return ret;
}
/**
* sys_sched_get_priority_min - return minimum RT priority.
* @policy: scheduling class.
*
* Return: On success, this syscall returns the minimum
* rt_priority that can be used by a given scheduling class.
* On failure, a negative error code is returned.
*/
SYSCALL_DEFINE1(sched_get_priority_min, int, policy)
{
int ret = -EINVAL;
switch (policy) {
case SCHED_FIFO:
case SCHED_RR:
ret = 1;
break;
case SCHED_DEADLINE:
case SCHED_NORMAL:
case SCHED_BATCH:
case SCHED_IDLE:
case SCHED_EXT:
ret = 0;
}
return ret;
}
static int sched_rr_get_interval(pid_t pid, struct timespec64 *t)
{
unsigned int time_slice = 0;
int retval;
if (pid < 0)
return -EINVAL;
scoped_guard (rcu) {
struct task_struct *p = find_process_by_pid(pid);
if (!p)
return -ESRCH;
retval = security_task_getscheduler(p);
if (retval)
return retval;
scoped_guard (task_rq_lock, p) {
struct rq *rq = scope.rq;
if (p->sched_class->get_rr_interval)
time_slice = p->sched_class->get_rr_interval(rq, p);
}
}
jiffies_to_timespec64(time_slice, t);
return 0;
}
/**
* sys_sched_rr_get_interval - return the default time-slice of a process.
* @pid: pid of the process.
* @interval: userspace pointer to the time-slice value.
*
* this syscall writes the default time-slice value of a given process
* into the user-space timespec buffer. A value of '0' means infinity.
*
* Return: On success, 0 and the time-slice is in @interval. Otherwise,
* an error code.
*/
SYSCALL_DEFINE2(sched_rr_get_interval, pid_t, pid,
struct __kernel_timespec __user *, interval)
{
struct timespec64 t;
int retval = sched_rr_get_interval(pid, &t);
if (retval == 0)
retval = put_timespec64(&t, interval);
return retval;
}
#ifdef CONFIG_COMPAT_32BIT_TIME
SYSCALL_DEFINE2(sched_rr_get_interval_time32, pid_t, pid,
struct old_timespec32 __user *, interval)
{
struct timespec64 t;
int retval = sched_rr_get_interval(pid, &t);
if (retval == 0)
retval = put_old_timespec32(&t, interval);
return retval;
}
#endif
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