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products/sources/formale Sprachen/C/Linux/kernel/ (Open Source Betriebssystem Version 6.17.9^©) Datei vom 24.10.2025 mit Größe 47 kB

Quelle kthread.c Sprache: C

// SPDX-License-Identifier: GPL-2.0-only
/* Kernel thread helper functions.
*   Copyright (C) 2004 IBM Corporation, Rusty Russell.
*   Copyright (C) 2009 Red Hat, Inc.
*
* Creation is done via kthreadd, so that we get a clean environment
* even if we're invoked from userspace (think modprobe, hotplug cpu,
* etc.).
*/
#include <uapi/linux/sched/types.h>
#include <linux/mm.h>
#include <linux/mmu_context.h>
#include <linux/sched.h>
#include <linux/sched/mm.h>
#include <linux/sched/task.h>
#include <linux/kthread.h>
#include <linux/completion.h>
#include <linux/err.h>
#include <linux/cgroup.h>
#include <linux/cpuset.h>
#include <linux/unistd.h>
#include <linux/file.h>
#include <linux/export.h>
#include <linux/mutex.h>
#include <linux/slab.h>
#include <linux/freezer.h>
#include <linux/ptrace.h>
#include <linux/uaccess.h>
#include <linux/numa.h>
#include <linux/sched/isolation.h>
#include <trace/events/sched.h>

static DEFINE_SPINLOCK(kthread_create_lock);
static LIST_HEAD(kthread_create_list);
struct task_struct *kthreadd_task;

static LIST_HEAD(kthreads_hotplug);
static DEFINE_MUTEX(kthreads_hotplug_lock);

struct kthread_create_info
{
/* Information passed to kthread() from kthreadd. */
char *full_name;
int (*threadfn)(void *data);
void *data;
int node;

/* Result passed back to kthread_create() from kthreadd. */
struct task_struct *result;
struct completion *done;

struct list_head list;
};

struct kthread {
unsigned long flags;
unsigned int cpu;
unsigned int node;
int started;
int result;
int (*threadfn)(void *);
void *data;
struct completion parked;
struct completion exited;
#ifdef CONFIG_BLK_CGROUP
struct cgroup_subsys_state *blkcg_css;
#endif
/* To store the full name if task comm is truncated. */
char *full_name;
struct task_struct *task;
struct list_head hotplug_node;
struct cpumask *preferred_affinity;
};

enum KTHREAD_BITS {
KTHREAD_IS_PER_CPU = 0,
KTHREAD_SHOULD_STOP,
KTHREAD_SHOULD_PARK,
};

static inline struct kthread *to_kthread(struct task_struct *k)
{
WARN_ON(!(k->flags & PF_KTHREAD));
return k->worker_private;
}

/*
* Variant of to_kthread() that doesn't assume @p is a kthread.
*
* When "(p->flags & PF_KTHREAD)" is set the task is a kthread and will
* always remain a kthread.  For kthreads p->worker_private always
* points to a struct kthread.  For tasks that are not kthreads
* p->worker_private is used to point to other things.
*
* Return NULL for any task that is not a kthread.
*/
static inline struct kthread *__to_kthread(struct task_struct *p)
{
void *kthread = p->worker_private;
if (kthread && !(p->flags & PF_KTHREAD))
  kthread = NULL;
return kthread;
}

void get_kthread_comm(char *buf, size_t buf_size, struct task_struct *tsk)
{
struct kthread *kthread = to_kthread(tsk);

if (!kthread || !kthread->full_name) {
  strscpy(buf, tsk->comm, buf_size);
  return;
}

strscpy_pad(buf, kthread->full_name, buf_size);
}

bool set_kthread_struct(struct task_struct *p)
{
struct kthread *kthread;

if (WARN_ON_ONCE(to_kthread(p)))
  return false;

kthread = kzalloc(sizeof(*kthread), GFP_KERNEL);
if (!kthread)
  return false;

init_completion(&kthread->exited);
init_completion(&kthread->parked);
INIT_LIST_HEAD(&kthread->hotplug_node);
p->vfork_done = &kthread->exited;

kthread->task = p;
kthread->node = tsk_fork_get_node(current);
p->worker_private = kthread;
return true;
}

void free_kthread_struct(struct task_struct *k)
{
struct kthread *kthread;

/*
* Can be NULL if kmalloc() in set_kthread_struct() failed.
*/
kthread = to_kthread(k);
if (!kthread)
  return;

#ifdef CONFIG_BLK_CGROUP
WARN_ON_ONCE(kthread->blkcg_css);
#endif
k->worker_private = NULL;
kfree(kthread->full_name);
kfree(kthread);
}

/**
* kthread_should_stop - should this kthread return now?
*
* When someone calls kthread_stop() on your kthread, it will be woken
* and this will return true.  You should then return, and your return
* value will be passed through to kthread_stop().
*/
bool kthread_should_stop(void)
{
return test_bit(KTHREAD_SHOULD_STOP, &to_kthread(current)->flags);
}
EXPORT_SYMBOL(kthread_should_stop);

static bool __kthread_should_park(struct task_struct *k)
{
return test_bit(KTHREAD_SHOULD_PARK, &to_kthread(k)->flags);
}

/**
* kthread_should_park - should this kthread park now?
*
* When someone calls kthread_park() on your kthread, it will be woken
* and this will return true.  You should then do the necessary
* cleanup and call kthread_parkme()
*
* Similar to kthread_should_stop(), but this keeps the thread alive
* and in a park position. kthread_unpark() "restarts" the thread and
* calls the thread function again.
*/
bool kthread_should_park(void)
{
return __kthread_should_park(current);
}
EXPORT_SYMBOL_GPL(kthread_should_park);

bool kthread_should_stop_or_park(void)
{
struct kthread *kthread = __to_kthread(current);

if (!kthread)
  return false;

return kthread->flags & (BIT(KTHREAD_SHOULD_STOP) | BIT(KTHREAD_SHOULD_PARK));
}

/**
* kthread_freezable_should_stop - should this freezable kthread return now?
* @was_frozen: optional out parameter, indicates whether %current was frozen
*
* kthread_should_stop() for freezable kthreads, which will enter
* refrigerator if necessary.  This function is safe from kthread_stop() /
* freezer deadlock and freezable kthreads should use this function instead
* of calling try_to_freeze() directly.
*/
bool kthread_freezable_should_stop(bool *was_frozen)
{
bool frozen = false;

might_sleep();

if (unlikely(freezing(current)))
  frozen = __refrigerator(true);

if (was_frozen)
  *was_frozen = frozen;

return kthread_should_stop();
}
EXPORT_SYMBOL_GPL(kthread_freezable_should_stop);

/**
* kthread_func - return the function specified on kthread creation
* @task: kthread task in question
*
* Returns NULL if the task is not a kthread.
*/
void *kthread_func(struct task_struct *task)
{
struct kthread *kthread = __to_kthread(task);
if (kthread)
  return kthread->threadfn;
return NULL;
}
EXPORT_SYMBOL_GPL(kthread_func);

/**
* kthread_data - return data value specified on kthread creation
* @task: kthread task in question
*
* Return the data value specified when kthread @task was created.
* The caller is responsible for ensuring the validity of @task when
* calling this function.
*/
void *kthread_data(struct task_struct *task)
{
return to_kthread(task)->data;
}
EXPORT_SYMBOL_GPL(kthread_data);

/**
* kthread_probe_data - speculative version of kthread_data()
* @task: possible kthread task in question
*
* @task could be a kthread task.  Return the data value specified when it
* was created if accessible.  If @task isn't a kthread task or its data is
* inaccessible for any reason, %NULL is returned.  This function requires
* that @task itself is safe to dereference.
*/
void *kthread_probe_data(struct task_struct *task)
{
struct kthread *kthread = __to_kthread(task);
void *data = NULL;

if (kthread)
  copy_from_kernel_nofault(&data, &kthread->data, sizeof(data));
return data;
}

static void __kthread_parkme(struct kthread *self)
{
for (;;) {
  /*
* TASK_PARKED is a special state; we must serialize against
* possible pending wakeups to avoid store-store collisions on
* task->state.
*
* Such a collision might possibly result in the task state
* changin from TASK_PARKED and us failing the
* wait_task_inactive() in kthread_park().
*/
  set_special_state(TASK_PARKED);
  if (!test_bit(KTHREAD_SHOULD_PARK, &self->flags))
   break;

  /*
* Thread is going to call schedule(), do not preempt it,
* or the caller of kthread_park() may spend more time in
* wait_task_inactive().
*/
  preempt_disable();
  complete(&self->parked);
  schedule_preempt_disabled();
  preempt_enable();
}
__set_current_state(TASK_RUNNING);
}

void kthread_parkme(void)
{
__kthread_parkme(to_kthread(current));
}
EXPORT_SYMBOL_GPL(kthread_parkme);

/**
* kthread_exit - Cause the current kthread return @result to kthread_stop().
* @result: The integer value to return to kthread_stop().
*
* While kthread_exit can be called directly, it exists so that
* functions which do some additional work in non-modular code such as
* module_put_and_kthread_exit can be implemented.
*
* Does not return.
*/
void __noreturn kthread_exit(long result)
{
struct kthread *kthread = to_kthread(current);
kthread->result = result;
if (!list_empty(&kthread->hotplug_node)) {
  mutex_lock(&kthreads_hotplug_lock);
  list_del(&kthread->hotplug_node);
  mutex_unlock(&kthreads_hotplug_lock);

  if (kthread->preferred_affinity) {
   kfree(kthread->preferred_affinity);
   kthread->preferred_affinity = NULL;
  }
}
do_exit(0);
}
EXPORT_SYMBOL(kthread_exit);

/**
* kthread_complete_and_exit - Exit the current kthread.
* @comp: Completion to complete
* @code: The integer value to return to kthread_stop().
*
* If present, complete @comp and then return code to kthread_stop().
*
* A kernel thread whose module may be removed after the completion of
* @comp can use this function to exit safely.
*
* Does not return.
*/
void __noreturn kthread_complete_and_exit(struct completion *comp, long code)
{
if (comp)
  complete(comp);

kthread_exit(code);
}
EXPORT_SYMBOL(kthread_complete_and_exit);

static void kthread_fetch_affinity(struct kthread *kthread, struct cpumask *cpumask)
{
const struct cpumask *pref;

if (kthread->preferred_affinity) {
  pref = kthread->preferred_affinity;
} else {
  if (WARN_ON_ONCE(kthread->node == NUMA_NO_NODE))
   return;
  pref = cpumask_of_node(kthread->node);
}

cpumask_and(cpumask, pref, housekeeping_cpumask(HK_TYPE_KTHREAD));
if (cpumask_empty(cpumask))
  cpumask_copy(cpumask, housekeeping_cpumask(HK_TYPE_KTHREAD));
}

static void kthread_affine_node(void)
{
struct kthread *kthread = to_kthread(current);
cpumask_var_t affinity;

WARN_ON_ONCE(kthread_is_per_cpu(current));

if (kthread->node == NUMA_NO_NODE) {
  housekeeping_affine(current, HK_TYPE_KTHREAD);
} else {
  if (!zalloc_cpumask_var(&affinity, GFP_KERNEL)) {
   WARN_ON_ONCE(1);
   return;
  }

  mutex_lock(&kthreads_hotplug_lock);
  WARN_ON_ONCE(!list_empty(&kthread->hotplug_node));
  list_add_tail(&kthread->hotplug_node, &kthreads_hotplug);
  /*
* The node cpumask is racy when read from kthread() but:
* - a racing CPU going down will either fail on the subsequent
*   call to set_cpus_allowed_ptr() or be migrated to housekeepers
*   afterwards by the scheduler.
* - a racing CPU going up will be handled by kthreads_online_cpu()
*/
  kthread_fetch_affinity(kthread, affinity);
  set_cpus_allowed_ptr(current, affinity);
  mutex_unlock(&kthreads_hotplug_lock);

  free_cpumask_var(affinity);
}
}

static int kthread(void *_create)
{
static const struct sched_param param = { .sched_priority = 0 };
/* Copy data: it's on kthread's stack */
struct kthread_create_info *create = _create;
int (*threadfn)(void *data) = create->threadfn;
void *data = create->data;
struct completion *done;
struct kthread *self;
int ret;

self = to_kthread(current);

/* Release the structure when caller killed by a fatal signal. */
done = xchg(&create->done, NULL);
if (!done) {
  kfree(create->full_name);
  kfree(create);
  kthread_exit(-EINTR);
}

self->full_name = create->full_name;
self->threadfn = threadfn;
self->data = data;

/*
* The new thread inherited kthreadd's priority and CPU mask. Reset
* back to default in case they have been changed.
*/
sched_setscheduler_nocheck(current, SCHED_NORMAL, ¶m);

/* OK, tell user we're spawned, wait for stop or wakeup */
__set_current_state(TASK_UNINTERRUPTIBLE);
create->result = current;
/*
* Thread is going to call schedule(), do not preempt it,
* or the creator may spend more time in wait_task_inactive().
*/
preempt_disable();
complete(done);
schedule_preempt_disabled();
preempt_enable();

self->started = 1;

if (!(current->flags & PF_NO_SETAFFINITY) && !self->preferred_affinity)
  kthread_affine_node();

ret = -EINTR;
if (!test_bit(KTHREAD_SHOULD_STOP, &self->flags)) {
  cgroup_kthread_ready();
  __kthread_parkme(self);
  ret = threadfn(data);
}
kthread_exit(ret);
}

/* called from kernel_clone() to get node information for about to be created task */
int tsk_fork_get_node(struct task_struct *tsk)
{
#ifdef CONFIG_NUMA
if (tsk == kthreadd_task)
  return tsk->pref_node_fork;
#endif
return NUMA_NO_NODE;
}

static void create_kthread(struct kthread_create_info *create)
{
int pid;

#ifdef CONFIG_NUMA
current->pref_node_fork = create->node;
#endif
/* We want our own signal handler (we take no signals by default). */
pid = kernel_thread(kthread, create, create->full_name,
       CLONE_FS | CLONE_FILES | SIGCHLD);
if (pid < 0) {
  /* Release the structure when caller killed by a fatal signal. */
  struct completion *done = xchg(&create->done, NULL);

  kfree(create->full_name);
  if (!done) {
   kfree(create);
   return;
  }
  create->result = ERR_PTR(pid);
  complete(done);
}
}

static __printf(4, 0)
struct task_struct *__kthread_create_on_node(int (*threadfn)(void *data),
          void *data, int node,
          const char namefmt[],
          va_list args)
{
DECLARE_COMPLETION_ONSTACK(done);
struct task_struct *task;
struct kthread_create_info *create = kmalloc(sizeof(*create),
           GFP_KERNEL);

if (!create)
  return ERR_PTR(-ENOMEM);
create->threadfn = threadfn;
create->data = data;
create->node = node;
create->done = &done;
create->full_name = kvasprintf(GFP_KERNEL, namefmt, args);
if (!create->full_name) {
  task = ERR_PTR(-ENOMEM);
  goto free_create;
}

spin_lock(&kthread_create_lock);
list_add_tail(&create->list, &kthread_create_list);
spin_unlock(&kthread_create_lock);

wake_up_process(kthreadd_task);
/*
* Wait for completion in killable state, for I might be chosen by
* the OOM killer while kthreadd is trying to allocate memory for
* new kernel thread.
*/
if (unlikely(wait_for_completion_killable(&done))) {
  /*
* If I was killed by a fatal signal before kthreadd (or new
* kernel thread) calls complete(), leave the cleanup of this
* structure to that thread.
*/
  if (xchg(&create->done, NULL))
   return ERR_PTR(-EINTR);
  /*
* kthreadd (or new kernel thread) will call complete()
* shortly.
*/
  wait_for_completion(&done);
}
task = create->result;
free_create:
kfree(create);
return task;
}

/**
* kthread_create_on_node - create a kthread.
* @threadfn: the function to run until signal_pending(current).
* @data: data ptr for @threadfn.
* @node: task and thread structures for the thread are allocated on this node
* @namefmt: printf-style name for the thread.
*
* Description: This helper function creates and names a kernel
* thread.  The thread will be stopped: use wake_up_process() to start
* it.  See also kthread_run().  The new thread has SCHED_NORMAL policy and
* is affine to all CPUs.
*
* If thread is going to be bound on a particular cpu, give its node
* in @node, to get NUMA affinity for kthread stack, or else give NUMA_NO_NODE.
* When woken, the thread will run @threadfn() with @data as its
* argument. @threadfn() can either return directly if it is a
* standalone thread for which no one will call kthread_stop(), or
* return when 'kthread_should_stop()' is true (which means
* kthread_stop() has been called).  The return value should be zero
* or a negative error number; it will be passed to kthread_stop().
*
* Returns a task_struct or ERR_PTR(-ENOMEM) or ERR_PTR(-EINTR).
*/
struct task_struct *kthread_create_on_node(int (*threadfn)(void *data),
        void *data, int node,
        const char namefmt[],
        ...)
{
struct task_struct *task;
va_list args;

va_start(args, namefmt);
task = __kthread_create_on_node(threadfn, data, node, namefmt, args);
va_end(args);

return task;
}
EXPORT_SYMBOL(kthread_create_on_node);

static void __kthread_bind_mask(struct task_struct *p, const struct cpumask *mask, unsigned int state)
{
unsigned long flags;

if (!wait_task_inactive(p, state)) {
  WARN_ON(1);
  return;
}

/* It's safe because the task is inactive. */
raw_spin_lock_irqsave(&p->pi_lock, flags);
do_set_cpus_allowed(p, mask);
p->flags |= PF_NO_SETAFFINITY;
raw_spin_unlock_irqrestore(&p->pi_lock, flags);
}

static void __kthread_bind(struct task_struct *p, unsigned int cpu, unsigned int state)
{
__kthread_bind_mask(p, cpumask_of(cpu), state);
}

void kthread_bind_mask(struct task_struct *p, const struct cpumask *mask)
{
struct kthread *kthread = to_kthread(p);
__kthread_bind_mask(p, mask, TASK_UNINTERRUPTIBLE);
WARN_ON_ONCE(kthread->started);
}

/**
* kthread_bind - bind a just-created kthread to a cpu.
* @p: thread created by kthread_create().
* @cpu: cpu (might not be online, must be possible) for @k to run on.
*
* Description: This function is equivalent to set_cpus_allowed(),
* except that @cpu doesn't need to be online, and the thread must be
* stopped (i.e., just returned from kthread_create()).
*/
void kthread_bind(struct task_struct *p, unsigned int cpu)
{
struct kthread *kthread = to_kthread(p);
__kthread_bind(p, cpu, TASK_UNINTERRUPTIBLE);
WARN_ON_ONCE(kthread->started);
}
EXPORT_SYMBOL(kthread_bind);

/**
* kthread_create_on_cpu - Create a cpu bound kthread
* @threadfn: the function to run until signal_pending(current).
* @data: data ptr for @threadfn.
* @cpu: The cpu on which the thread should be bound,
* @namefmt: printf-style name for the thread. Format is restricted
*      to "name.*%u". Code fills in cpu number.
*
* Description: This helper function creates and names a kernel thread
*/
struct task_struct *kthread_create_on_cpu(int (*threadfn)(void *data),
       void *data, unsigned int cpu,
       const char *namefmt)
{
struct task_struct *p;

p = kthread_create_on_node(threadfn, data, cpu_to_node(cpu), namefmt,
       cpu);
if (IS_ERR(p))
  return p;
kthread_bind(p, cpu);
/* CPU hotplug need to bind once again when unparking the thread. */
to_kthread(p)->cpu = cpu;
return p;
}
EXPORT_SYMBOL(kthread_create_on_cpu);

void kthread_set_per_cpu(struct task_struct *k, int cpu)
{
struct kthread *kthread = to_kthread(k);
if (!kthread)
  return;

WARN_ON_ONCE(!(k->flags & PF_NO_SETAFFINITY));

if (cpu < 0) {
  clear_bit(KTHREAD_IS_PER_CPU, &kthread->flags);
  return;
}

kthread->cpu = cpu;
set_bit(KTHREAD_IS_PER_CPU, &kthread->flags);
}

bool kthread_is_per_cpu(struct task_struct *p)
{
struct kthread *kthread = __to_kthread(p);
if (!kthread)
  return false;

return test_bit(KTHREAD_IS_PER_CPU, &kthread->flags);
}

/**
* kthread_unpark - unpark a thread created by kthread_create().
* @k: thread created by kthread_create().
*
* Sets kthread_should_park() for @k to return false, wakes it, and
* waits for it to return. If the thread is marked percpu then its
* bound to the cpu again.
*/
void kthread_unpark(struct task_struct *k)
{
struct kthread *kthread = to_kthread(k);

if (!test_bit(KTHREAD_SHOULD_PARK, &kthread->flags))
  return;
/*
* Newly created kthread was parked when the CPU was offline.
* The binding was lost and we need to set it again.
*/
if (test_bit(KTHREAD_IS_PER_CPU, &kthread->flags))
  __kthread_bind(k, kthread->cpu, TASK_PARKED);

clear_bit(KTHREAD_SHOULD_PARK, &kthread->flags);
/*
* __kthread_parkme() will either see !SHOULD_PARK or get the wakeup.
*/
wake_up_state(k, TASK_PARKED);
}
EXPORT_SYMBOL_GPL(kthread_unpark);

/**
* kthread_park - park a thread created by kthread_create().
* @k: thread created by kthread_create().
*
* Sets kthread_should_park() for @k to return true, wakes it, and
* waits for it to return. This can also be called after kthread_create()
* instead of calling wake_up_process(): the thread will park without
* calling threadfn().
*
* Returns 0 if the thread is parked, -ENOSYS if the thread exited.
* If called by the kthread itself just the park bit is set.
*/
int kthread_park(struct task_struct *k)
{
struct kthread *kthread = to_kthread(k);

if (WARN_ON(k->flags & PF_EXITING))
  return -ENOSYS;

if (WARN_ON_ONCE(test_bit(KTHREAD_SHOULD_PARK, &kthread->flags)))
  return -EBUSY;

set_bit(KTHREAD_SHOULD_PARK, &kthread->flags);
if (k != current) {
  wake_up_process(k);
  /*
* Wait for __kthread_parkme() to complete(), this means we
* _will_ have TASK_PARKED and are about to call schedule().
*/
  wait_for_completion(&kthread->parked);
  /*
* Now wait for that schedule() to complete and the task to
* get scheduled out.
*/
  WARN_ON_ONCE(!wait_task_inactive(k, TASK_PARKED));
}

return 0;
}
EXPORT_SYMBOL_GPL(kthread_park);

/**
* kthread_stop - stop a thread created by kthread_create().
* @k: thread created by kthread_create().
*
* Sets kthread_should_stop() for @k to return true, wakes it, and
* waits for it to exit. This can also be called after kthread_create()
* instead of calling wake_up_process(): the thread will exit without
* calling threadfn().
*
* If threadfn() may call kthread_exit() itself, the caller must ensure
* task_struct can't go away.
*
* Returns the result of threadfn(), or %-EINTR if wake_up_process()
* was never called.
*/
int kthread_stop(struct task_struct *k)
{
struct kthread *kthread;
int ret;

trace_sched_kthread_stop(k);

get_task_struct(k);
kthread = to_kthread(k);
set_bit(KTHREAD_SHOULD_STOP, &kthread->flags);
kthread_unpark(k);
set_tsk_thread_flag(k, TIF_NOTIFY_SIGNAL);
wake_up_process(k);
wait_for_completion(&kthread->exited);
ret = kthread->result;
put_task_struct(k);

trace_sched_kthread_stop_ret(ret);
return ret;
}
EXPORT_SYMBOL(kthread_stop);

/**
* kthread_stop_put - stop a thread and put its task struct
* @k: thread created by kthread_create().
*
* Stops a thread created by kthread_create() and put its task_struct.
* Only use when holding an extra task struct reference obtained by
* calling get_task_struct().
*/
int kthread_stop_put(struct task_struct *k)
{
int ret;

ret = kthread_stop(k);
put_task_struct(k);
return ret;
}
EXPORT_SYMBOL(kthread_stop_put);

int kthreadd(void *unused)
{
static const char comm[TASK_COMM_LEN] = "kthreadd";
struct task_struct *tsk = current;

/* Setup a clean context for our children to inherit. */
set_task_comm(tsk, comm);
ignore_signals(tsk);
set_cpus_allowed_ptr(tsk, housekeeping_cpumask(HK_TYPE_KTHREAD));
set_mems_allowed(node_states[N_MEMORY]);

current->flags |= PF_NOFREEZE;
cgroup_init_kthreadd();

for (;;) {
  set_current_state(TASK_INTERRUPTIBLE);
  if (list_empty(&kthread_create_list))
   schedule();
  __set_current_state(TASK_RUNNING);

  spin_lock(&kthread_create_lock);
  while (!list_empty(&kthread_create_list)) {
   struct kthread_create_info *create;

   create = list_entry(kthread_create_list.next,
         struct kthread_create_info, list);
   list_del_init(&create->list);
   spin_unlock(&kthread_create_lock);

   create_kthread(create);

   spin_lock(&kthread_create_lock);
  }
  spin_unlock(&kthread_create_lock);
}

return 0;
}

int kthread_affine_preferred(struct task_struct *p, const struct cpumask *mask)
{
struct kthread *kthread = to_kthread(p);
cpumask_var_t affinity;
unsigned long flags;
int ret = 0;

if (!wait_task_inactive(p, TASK_UNINTERRUPTIBLE) || kthread->started) {
  WARN_ON(1);
  return -EINVAL;
}

WARN_ON_ONCE(kthread->preferred_affinity);

if (!zalloc_cpumask_var(&affinity, GFP_KERNEL))
  return -ENOMEM;

kthread->preferred_affinity = kzalloc(sizeof(struct cpumask), GFP_KERNEL);
if (!kthread->preferred_affinity) {
  ret = -ENOMEM;
  goto out;
}

mutex_lock(&kthreads_hotplug_lock);
cpumask_copy(kthread->preferred_affinity, mask);
WARN_ON_ONCE(!list_empty(&kthread->hotplug_node));
list_add_tail(&kthread->hotplug_node, &kthreads_hotplug);
kthread_fetch_affinity(kthread, affinity);

/* It's safe because the task is inactive. */
raw_spin_lock_irqsave(&p->pi_lock, flags);
do_set_cpus_allowed(p, affinity);
raw_spin_unlock_irqrestore(&p->pi_lock, flags);

mutex_unlock(&kthreads_hotplug_lock);
out:
free_cpumask_var(affinity);

return ret;
}
EXPORT_SYMBOL_GPL(kthread_affine_preferred);

/*
* Re-affine kthreads according to their preferences
* and the newly online CPU. The CPU down part is handled
* by select_fallback_rq() which default re-affines to
* housekeepers from other nodes in case the preferred
* affinity doesn't apply anymore.
*/
static int kthreads_online_cpu(unsigned int cpu)
{
cpumask_var_t affinity;
struct kthread *k;
int ret;

guard(mutex)(&kthreads_hotplug_lock);

if (list_empty(&kthreads_hotplug))
  return 0;

if (!zalloc_cpumask_var(&affinity, GFP_KERNEL))
  return -ENOMEM;

ret = 0;

list_for_each_entry(k, &kthreads_hotplug, hotplug_node) {
  if (WARN_ON_ONCE((k->task->flags & PF_NO_SETAFFINITY) ||
     kthread_is_per_cpu(k->task))) {
   ret = -EINVAL;
   continue;
  }
  kthread_fetch_affinity(k, affinity);
  set_cpus_allowed_ptr(k->task, affinity);
}

free_cpumask_var(affinity);

return ret;
}

static int kthreads_init(void)
{
return cpuhp_setup_state(CPUHP_AP_KTHREADS_ONLINE, "kthreads:online",
    kthreads_online_cpu, NULL);
}
early_initcall(kthreads_init);

void __kthread_init_worker(struct kthread_worker *worker,
    const char *name,
    struct lock_class_key *key)
{
memset(worker, 0, sizeof(struct kthread_worker));
raw_spin_lock_init(&worker->lock);
lockdep_set_class_and_name(&worker->lock, key, name);
INIT_LIST_HEAD(&worker->work_list);
INIT_LIST_HEAD(&worker->delayed_work_list);
}
EXPORT_SYMBOL_GPL(__kthread_init_worker);

/**
* kthread_worker_fn - kthread function to process kthread_worker
* @worker_ptr: pointer to initialized kthread_worker
*
* This function implements the main cycle of kthread worker. It processes
* work_list until it is stopped with kthread_stop(). It sleeps when the queue
* is empty.
*
* The works are not allowed to keep any locks, disable preemption or interrupts
* when they finish. There is defined a safe point for freezing when one work
* finishes and before a new one is started.
*
* Also the works must not be handled by more than one worker at the same time,
* see also kthread_queue_work().
*/
int kthread_worker_fn(void *worker_ptr)
{
struct kthread_worker *worker = worker_ptr;
struct kthread_work *work;

/*
* FIXME: Update the check and remove the assignment when all kthread
* worker users are created using kthread_create_worker*() functions.
*/
WARN_ON(worker->task && worker->task != current);
worker->task = current;

if (worker->flags & KTW_FREEZABLE)
  set_freezable();

repeat:
set_current_state(TASK_INTERRUPTIBLE); /* mb paired w/ kthread_stop */

if (kthread_should_stop()) {
  __set_current_state(TASK_RUNNING);
  raw_spin_lock_irq(&worker->lock);
  worker->task = NULL;
  raw_spin_unlock_irq(&worker->lock);
  return 0;
}

work = NULL;
raw_spin_lock_irq(&worker->lock);
if (!list_empty(&worker->work_list)) {
  work = list_first_entry(&worker->work_list,
     struct kthread_work, node);
  list_del_init(&work->node);
}
worker->current_work = work;
raw_spin_unlock_irq(&worker->lock);

if (work) {
  kthread_work_func_t func = work->func;
  __set_current_state(TASK_RUNNING);
  trace_sched_kthread_work_execute_start(work);
  work->func(work);
  /*
* Avoid dereferencing work after this point.  The trace
* event only cares about the address.
*/
  trace_sched_kthread_work_execute_end(work, func);
} else if (!freezing(current)) {
  schedule();
} else {
  /*
* Handle the case where the current remains
* TASK_INTERRUPTIBLE. try_to_freeze() expects
* the current to be TASK_RUNNING.
*/
  __set_current_state(TASK_RUNNING);
}

try_to_freeze();
cond_resched();
goto repeat;
}
EXPORT_SYMBOL_GPL(kthread_worker_fn);

static __printf(3, 0) struct kthread_worker *
__kthread_create_worker_on_node(unsigned int flags, int node,
    const char namefmt[], va_list args)
{
struct kthread_worker *worker;
struct task_struct *task;

worker = kzalloc(sizeof(*worker), GFP_KERNEL);
if (!worker)
  return ERR_PTR(-ENOMEM);

kthread_init_worker(worker);

task = __kthread_create_on_node(kthread_worker_fn, worker,
     node, namefmt, args);
if (IS_ERR(task))
  goto fail_task;

worker->flags = flags;
worker->task = task;

return worker;

fail_task:
kfree(worker);
return ERR_CAST(task);
}

/**
* kthread_create_worker_on_node - create a kthread worker
* @flags: flags modifying the default behavior of the worker
* @node: task structure for the thread is allocated on this node
* @namefmt: printf-style name for the kthread worker (task).
*
* Returns a pointer to the allocated worker on success, ERR_PTR(-ENOMEM)
* when the needed structures could not get allocated, and ERR_PTR(-EINTR)
* when the caller was killed by a fatal signal.
*/
struct kthread_worker *
kthread_create_worker_on_node(unsigned int flags, int node, const char namefmt[], ...)
{
struct kthread_worker *worker;
va_list args;

va_start(args, namefmt);
worker = __kthread_create_worker_on_node(flags, node, namefmt, args);
va_end(args);

return worker;
}
EXPORT_SYMBOL(kthread_create_worker_on_node);

/**
* kthread_create_worker_on_cpu - create a kthread worker and bind it
* to a given CPU and the associated NUMA node.
* @cpu: CPU number
* @flags: flags modifying the default behavior of the worker
* @namefmt: printf-style name for the thread. Format is restricted
*      to "name.*%u". Code fills in cpu number.
*
* Use a valid CPU number if you want to bind the kthread worker
* to the given CPU and the associated NUMA node.
*
* A good practice is to add the cpu number also into the worker name.
* For example, use kthread_create_worker_on_cpu(cpu, "helper/%d", cpu).
*
* CPU hotplug:
* The kthread worker API is simple and generic. It just provides a way
* to create, use, and destroy workers.
*
* It is up to the API user how to handle CPU hotplug. They have to decide
* how to handle pending work items, prevent queuing new ones, and
* restore the functionality when the CPU goes off and on. There are a
* few catches:
*
*    - CPU affinity gets lost when it is scheduled on an offline CPU.
*
*    - The worker might not exist when the CPU was off when the user
*      created the workers.
*
* Good practice is to implement two CPU hotplug callbacks and to
* destroy/create the worker when the CPU goes down/up.
*
* Return:
* The pointer to the allocated worker on success, ERR_PTR(-ENOMEM)
* when the needed structures could not get allocated, and ERR_PTR(-EINTR)
* when the caller was killed by a fatal signal.
*/
struct kthread_worker *
kthread_create_worker_on_cpu(int cpu, unsigned int flags,
        const char namefmt[])
{
struct kthread_worker *worker;

worker = kthread_create_worker_on_node(flags, cpu_to_node(cpu), namefmt, cpu);
if (!IS_ERR(worker))
  kthread_bind(worker->task, cpu);

return worker;
}
EXPORT_SYMBOL(kthread_create_worker_on_cpu);

/*
* Returns true when the work could not be queued at the moment.
* It happens when it is already pending in a worker list
* or when it is being cancelled.
*/
static inline bool queuing_blocked(struct kthread_worker *worker,
       struct kthread_work *work)
{
lockdep_assert_held(&worker->lock);

return !list_empty(&work->node) || work->canceling;
}

static void kthread_insert_work_sanity_check(struct kthread_worker *worker,
          struct kthread_work *work)
{
lockdep_assert_held(&worker->lock);
WARN_ON_ONCE(!list_empty(&work->node));
/* Do not use a work with >1 worker, see kthread_queue_work() */
WARN_ON_ONCE(work->worker && work->worker != worker);
}

/* insert @work before @pos in @worker */
static void kthread_insert_work(struct kthread_worker *worker,
    struct kthread_work *work,
    struct list_head *pos)
{
kthread_insert_work_sanity_check(worker, work);

trace_sched_kthread_work_queue_work(worker, work);

list_add_tail(&work->node, pos);
work->worker = worker;
if (!worker->current_work && likely(worker->task))
  wake_up_process(worker->task);
}

/**
* kthread_queue_work - queue a kthread_work
* @worker: target kthread_worker
* @work: kthread_work to queue
*
* Queue @work to work processor @task for async execution.  @task
* must have been created with kthread_create_worker().  Returns %true
* if @work was successfully queued, %false if it was already pending.
*
* Reinitialize the work if it needs to be used by another worker.
* For example, when the worker was stopped and started again.
*/
bool kthread_queue_work(struct kthread_worker *worker,
   struct kthread_work *work)
{
bool ret = false;
unsigned long flags;

raw_spin_lock_irqsave(&worker->lock, flags);
if (!queuing_blocked(worker, work)) {
  kthread_insert_work(worker, work, &worker->work_list);
  ret = true;
}
raw_spin_unlock_irqrestore(&worker->lock, flags);
return ret;
}
EXPORT_SYMBOL_GPL(kthread_queue_work);

/**
* kthread_delayed_work_timer_fn - callback that queues the associated kthread
* delayed work when the timer expires.
* @t: pointer to the expired timer
*
* The format of the function is defined by struct timer_list.
* It should have been called from irqsafe timer with irq already off.
*/
void kthread_delayed_work_timer_fn(struct timer_list *t)
{
struct kthread_delayed_work *dwork = timer_container_of(dwork, t,
        timer);
struct kthread_work *work = &dwork->work;
struct kthread_worker *worker = work->worker;
unsigned long flags;

/*
* This might happen when a pending work is reinitialized.
* It means that it is used a wrong way.
*/
if (WARN_ON_ONCE(!worker))
  return;

raw_spin_lock_irqsave(&worker->lock, flags);
/* Work must not be used with >1 worker, see kthread_queue_work(). */
WARN_ON_ONCE(work->worker != worker);

/* Move the work from worker->delayed_work_list. */
WARN_ON_ONCE(list_empty(&work->node));
list_del_init(&work->node);
if (!work->canceling)
  kthread_insert_work(worker, work, &worker->work_list);

raw_spin_unlock_irqrestore(&worker->lock, flags);
}
EXPORT_SYMBOL(kthread_delayed_work_timer_fn);

static void __kthread_queue_delayed_work(struct kthread_worker *worker,
      struct kthread_delayed_work *dwork,
      unsigned long delay)
{
struct timer_list *timer = &dwork->timer;
struct kthread_work *work = &dwork->work;

WARN_ON_ONCE(timer->function != kthread_delayed_work_timer_fn);

/*
* If @delay is 0, queue @dwork->work immediately.  This is for
* both optimization and correctness.  The earliest @timer can
* expire is on the closest next tick and delayed_work users depend
* on that there's no such delay when @delay is 0.
*/
if (!delay) {
  kthread_insert_work(worker, work, &worker->work_list);
  return;
}

/* Be paranoid and try to detect possible races already now. */
kthread_insert_work_sanity_check(worker, work);

list_add(&work->node, &worker->delayed_work_list);
work->worker = worker;
timer->expires = jiffies + delay;
add_timer(timer);
}

/**
* kthread_queue_delayed_work - queue the associated kthread work
* after a delay.
* @worker: target kthread_worker
* @dwork: kthread_delayed_work to queue
* @delay: number of jiffies to wait before queuing
*
* If the work has not been pending it starts a timer that will queue
* the work after the given @delay. If @delay is zero, it queues the
* work immediately.
*
* Return: %false if the @work has already been pending. It means that
* either the timer was running or the work was queued. It returns %true
* otherwise.
*/
bool kthread_queue_delayed_work(struct kthread_worker *worker,
    struct kthread_delayed_work *dwork,
    unsigned long delay)
{
struct kthread_work *work = &dwork->work;
unsigned long flags;
bool ret = false;

raw_spin_lock_irqsave(&worker->lock, flags);

if (!queuing_blocked(worker, work)) {
  __kthread_queue_delayed_work(worker, dwork, delay);
  ret = true;
}

raw_spin_unlock_irqrestore(&worker->lock, flags);
return ret;
}
EXPORT_SYMBOL_GPL(kthread_queue_delayed_work);

struct kthread_flush_work {
struct kthread_work work;
struct completion done;
};

static void kthread_flush_work_fn(struct kthread_work *work)
{
struct kthread_flush_work *fwork =
  container_of(work, struct kthread_flush_work, work);
complete(&fwork->done);
}

/**
* kthread_flush_work - flush a kthread_work
* @work: work to flush
*
* If @work is queued or executing, wait for it to finish execution.
*/
void kthread_flush_work(struct kthread_work *work)
{
struct kthread_flush_work fwork = {
  KTHREAD_WORK_INIT(fwork.work, kthread_flush_work_fn),
  COMPLETION_INITIALIZER_ONSTACK(fwork.done),
};
struct kthread_worker *worker;
bool noop = false;

worker = work->worker;
if (!worker)
  return;

raw_spin_lock_irq(&worker->lock);
/* Work must not be used with >1 worker, see kthread_queue_work(). */
WARN_ON_ONCE(work->worker != worker);

if (!list_empty(&work->node))
  kthread_insert_work(worker, &fwork.work, work->node.next);
else if (worker->current_work == work)
  kthread_insert_work(worker, &fwork.work,
        worker->work_list.next);
else
  noop = true;

raw_spin_unlock_irq(&worker->lock);

if (!noop)
  wait_for_completion(&fwork.done);
}
EXPORT_SYMBOL_GPL(kthread_flush_work);

/*
* Make sure that the timer is neither set nor running and could
* not manipulate the work list_head any longer.
*
* The function is called under worker->lock. The lock is temporary
* released but the timer can't be set again in the meantime.
*/
static void kthread_cancel_delayed_work_timer(struct kthread_work *work,
           unsigned long *flags)
{
struct kthread_delayed_work *dwork =
  container_of(work, struct kthread_delayed_work, work);
struct kthread_worker *worker = work->worker;

/*
* timer_delete_sync() must be called to make sure that the timer
* callback is not running. The lock must be temporary released
* to avoid a deadlock with the callback. In the meantime,
* any queuing is blocked by setting the canceling counter.
*/
work->canceling++;
raw_spin_unlock_irqrestore(&worker->lock, *flags);
timer_delete_sync(&dwork->timer);
raw_spin_lock_irqsave(&worker->lock, *flags);
work->canceling--;
}

/*
* This function removes the work from the worker queue.
*
* It is called under worker->lock. The caller must make sure that
* the timer used by delayed work is not running, e.g. by calling
* kthread_cancel_delayed_work_timer().
*
* The work might still be in use when this function finishes. See the
* current_work proceed by the worker.
*
* Return: %true if @work was pending and successfully canceled,
* %false if @work was not pending
*/
static bool __kthread_cancel_work(struct kthread_work *work)
{
/*
* Try to remove the work from a worker list. It might either
* be from worker->work_list or from worker->delayed_work_list.
*/
if (!list_empty(&work->node)) {
  list_del_init(&work->node);
  return true;
}

return false;
}

/**
* kthread_mod_delayed_work - modify delay of or queue a kthread delayed work
* @worker: kthread worker to use
* @dwork: kthread delayed work to queue
* @delay: number of jiffies to wait before queuing
*
* If @dwork is idle, equivalent to kthread_queue_delayed_work(). Otherwise,
* modify @dwork's timer so that it expires after @delay. If @delay is zero,
* @work is guaranteed to be queued immediately.
*
* Return: %false if @dwork was idle and queued, %true otherwise.
*
* A special case is when the work is being canceled in parallel.
* It might be caused either by the real kthread_cancel_delayed_work_sync()
* or yet another kthread_mod_delayed_work() call. We let the other command
* win and return %true here. The return value can be used for reference
* counting and the number of queued works stays the same. Anyway, the caller
* is supposed to synchronize these operations a reasonable way.
*
* This function is safe to call from any context including IRQ handler.
* See __kthread_cancel_work() and kthread_delayed_work_timer_fn()
* for details.
*/
bool kthread_mod_delayed_work(struct kthread_worker *worker,
         struct kthread_delayed_work *dwork,
         unsigned long delay)
{
struct kthread_work *work = &dwork->work;
unsigned long flags;
int ret;

raw_spin_lock_irqsave(&worker->lock, flags);

/* Do not bother with canceling when never queued. */
if (!work->worker) {
  ret = false;
  goto fast_queue;
}

/* Work must not be used with >1 worker, see kthread_queue_work() */
WARN_ON_ONCE(work->worker != worker);

/*
* Temporary cancel the work but do not fight with another command
* that is canceling the work as well.
*
* It is a bit tricky because of possible races with another
* mod_delayed_work() and cancel_delayed_work() callers.
*
* The timer must be canceled first because worker->lock is released
* when doing so. But the work can be removed from the queue (list)
* only when it can be queued again so that the return value can
* be used for reference counting.
*/
kthread_cancel_delayed_work_timer(work, &flags);
if (work->canceling) {
  /* The number of works in the queue does not change. */
  ret = true;
  goto out;
}
ret = __kthread_cancel_work(work);

fast_queue:
__kthread_queue_delayed_work(worker, dwork, delay);
out:
raw_spin_unlock_irqrestore(&worker->lock, flags);
return ret;
}
EXPORT_SYMBOL_GPL(kthread_mod_delayed_work);

static bool __kthread_cancel_work_sync(struct kthread_work *work, bool is_dwork)
{
struct kthread_worker *worker = work->worker;
unsigned long flags;
int ret = false;

if (!worker)
  goto out;

raw_spin_lock_irqsave(&worker->lock, flags);
/* Work must not be used with >1 worker, see kthread_queue_work(). */
WARN_ON_ONCE(work->worker != worker);

if (is_dwork)
  kthread_cancel_delayed_work_timer(work, &flags);

ret = __kthread_cancel_work(work);

if (worker->current_work != work)
  goto out_fast;

/*
* The work is in progress and we need to wait with the lock released.
* In the meantime, block any queuing by setting the canceling counter.
*/
work->canceling++;
raw_spin_unlock_irqrestore(&worker->lock, flags);
kthread_flush_work(work);
raw_spin_lock_irqsave(&worker->lock, flags);
work->canceling--;

out_fast:
raw_spin_unlock_irqrestore(&worker->lock, flags);
out:
return ret;
}

/**
* kthread_cancel_work_sync - cancel a kthread work and wait for it to finish
* @work: the kthread work to cancel
*
* Cancel @work and wait for its execution to finish.  This function
* can be used even if the work re-queues itself. On return from this
* function, @work is guaranteed to be not pending or executing on any CPU.
*
* kthread_cancel_work_sync(&delayed_work->work) must not be used for
* delayed_work's. Use kthread_cancel_delayed_work_sync() instead.
*
* The caller must ensure that the worker on which @work was last
* queued can't be destroyed before this function returns.
*
* Return: %true if @work was pending, %false otherwise.
*/
bool kthread_cancel_work_sync(struct kthread_work *work)
{
return __kthread_cancel_work_sync(work, false);
}
EXPORT_SYMBOL_GPL(kthread_cancel_work_sync);

/**
* kthread_cancel_delayed_work_sync - cancel a kthread delayed work and
* wait for it to finish.
* @dwork: the kthread delayed work to cancel
*
* This is kthread_cancel_work_sync() for delayed works.
*
* Return: %true if @dwork was pending, %false otherwise.
*/
bool kthread_cancel_delayed_work_sync(struct kthread_delayed_work *dwork)
{
return __kthread_cancel_work_sync(&dwork->work, true);
}
EXPORT_SYMBOL_GPL(kthread_cancel_delayed_work_sync);

/**
* kthread_flush_worker - flush all current works on a kthread_worker
* @worker: worker to flush
*
* Wait until all currently executing or pending works on @worker are
* finished.
*/
void kthread_flush_worker(struct kthread_worker *worker)
{
struct kthread_flush_work fwork = {
  KTHREAD_WORK_INIT(fwork.work, kthread_flush_work_fn),
  COMPLETION_INITIALIZER_ONSTACK(fwork.done),
};

kthread_queue_work(worker, &fwork.work);
wait_for_completion(&fwork.done);
}
EXPORT_SYMBOL_GPL(kthread_flush_worker);

/**
* kthread_destroy_worker - destroy a kthread worker
* @worker: worker to be destroyed
*
* Flush and destroy @worker.  The simple flush is enough because the kthread
* worker API is used only in trivial scenarios.  There are no multi-step state
* machines needed.
*
* Note that this function is not responsible for handling delayed work, so
* caller should be responsible for queuing or canceling all delayed work items
* before invoke this function.
*/
void kthread_destroy_worker(struct kthread_worker *worker)
{
struct task_struct *task;

task = worker->task;
if (WARN_ON(!task))
  return;

kthread_flush_worker(worker);
kthread_stop(task);
WARN_ON(!list_empty(&worker->delayed_work_list));
WARN_ON(!list_empty(&worker->work_list));
kfree(worker);
}
EXPORT_SYMBOL(kthread_destroy_worker);

/**
* kthread_use_mm - make the calling kthread operate on an address space
* @mm: address space to operate on
*/
void kthread_use_mm(struct mm_struct *mm)
{
struct mm_struct *active_mm;
struct task_struct *tsk = current;

WARN_ON_ONCE(!(tsk->flags & PF_KTHREAD));
WARN_ON_ONCE(tsk->mm);

/*
* It is possible for mm to be the same as tsk->active_mm, but
* we must still mmgrab(mm) and mmdrop_lazy_tlb(active_mm),
* because these references are not equivalent.
*/
mmgrab(mm);

task_lock(tsk);
/* Hold off tlb flush IPIs while switching mm's */
local_irq_disable();
active_mm = tsk->active_mm;
tsk->active_mm = mm;
tsk->mm = mm;
membarrier_update_current_mm(mm);
switch_mm_irqs_off(active_mm, mm, tsk);
local_irq_enable();
task_unlock(tsk);
#ifdef finish_arch_post_lock_switch
finish_arch_post_lock_switch();
#endif

/*
* When a kthread starts operating on an address space, the loop
* in membarrier_{private,global}_expedited() may not observe
* that tsk->mm, and not issue an IPI. Membarrier requires a
* memory barrier after storing to tsk->mm, before accessing
* user-space memory. A full memory barrier for membarrier
* {PRIVATE,GLOBAL}_EXPEDITED is implicitly provided by
* mmdrop_lazy_tlb().
*/
mmdrop_lazy_tlb(active_mm);
}
EXPORT_SYMBOL_GPL(kthread_use_mm);

/**
* kthread_unuse_mm - reverse the effect of kthread_use_mm()
* @mm: address space to operate on
*/
void kthread_unuse_mm(struct mm_struct *mm)
{
struct task_struct *tsk = current;

WARN_ON_ONCE(!(tsk->flags & PF_KTHREAD));
WARN_ON_ONCE(!tsk->mm);

task_lock(tsk);
/*
* When a kthread stops operating on an address space, the loop
* in membarrier_{private,global}_expedited() may not observe
* that tsk->mm, and not issue an IPI. Membarrier requires a
* memory barrier after accessing user-space memory, before
* clearing tsk->mm.
*/
smp_mb__after_spinlock();
local_irq_disable();
tsk->mm = NULL;
membarrier_update_current_mm(NULL);
mmgrab_lazy_tlb(mm);
/* active_mm is still 'mm' */
enter_lazy_tlb(mm, tsk);
local_irq_enable();
task_unlock(tsk);

mmdrop(mm);
}
EXPORT_SYMBOL_GPL(kthread_unuse_mm);

#ifdef CONFIG_BLK_CGROUP
/**
* kthread_associate_blkcg - associate blkcg to current kthread
* @css: the cgroup info
*
* Current thread must be a kthread. The thread is running jobs on behalf of
* other threads. In some cases, we expect the jobs attach cgroup info of
* original threads instead of that of current thread. This function stores
* original thread's cgroup info in current kthread context for later
* retrieval.
*/
void kthread_associate_blkcg(struct cgroup_subsys_state *css)
{
struct kthread *kthread;

if (!(current->flags & PF_KTHREAD))
  return;
kthread = to_kthread(current);
if (!kthread)
  return;

if (kthread->blkcg_css) {
  css_put(kthread->blkcg_css);
  kthread->blkcg_css = NULL;
}
if (css) {
  css_get(css);
  kthread->blkcg_css = css;
}
}
EXPORT_SYMBOL(kthread_associate_blkcg);

/**
* kthread_blkcg - get associated blkcg css of current kthread
*
* Current thread must be a kthread.
*/
struct cgroup_subsys_state *kthread_blkcg(void)
{
struct kthread *kthread;

if (current->flags & PF_KTHREAD) {
  kthread = to_kthread(current);
  if (kthread)
   return kthread->blkcg_css;
}
return NULL;
}
#endif

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