[mirror_ubuntu-bionic-kernel.git] / include / linux / workqueue.h

/* SPDX-License-Identifier: GPL-2.0 */
/*
 * workqueue.h --- work queue handling for Linux.
 */

#ifndef _LINUX_WORKQUEUE_H
#define _LINUX_WORKQUEUE_H

#include <linux/timer.h>
#include <linux/linkage.h>
#include <linux/bitops.h>
#include <linux/lockdep.h>
#include <linux/threads.h>
#include <linux/atomic.h>
#include <linux/cpumask.h>

struct workqueue_struct;

struct work_struct;
typedef void (*work_func_t)(struct work_struct *work);
void delayed_work_timer_fn(struct timer_list *t);

/*
 * The first word is the work queue pointer and the flags rolled into
 * one
 */
#define work_data_bits(work) ((unsigned long *)(&(work)->data))

enum {
        WORK_STRUCT_PENDING_BIT = 0,    /* work item is pending execution */
        WORK_STRUCT_DELAYED_BIT = 1,    /* work item is delayed */
        WORK_STRUCT_PWQ_BIT     = 2,    /* data points to pwq */
        WORK_STRUCT_LINKED_BIT  = 3,    /* next work is linked to this one */
#ifdef CONFIG_DEBUG_OBJECTS_WORK
        WORK_STRUCT_STATIC_BIT  = 4,    /* static initializer (debugobjects) */
        WORK_STRUCT_COLOR_SHIFT = 5,    /* color for workqueue flushing */
#else
        WORK_STRUCT_COLOR_SHIFT = 4,    /* color for workqueue flushing */
#endif

        WORK_STRUCT_COLOR_BITS  = 4,

        WORK_STRUCT_PENDING     = 1 << WORK_STRUCT_PENDING_BIT,
        WORK_STRUCT_DELAYED     = 1 << WORK_STRUCT_DELAYED_BIT,
        WORK_STRUCT_PWQ         = 1 << WORK_STRUCT_PWQ_BIT,
        WORK_STRUCT_LINKED      = 1 << WORK_STRUCT_LINKED_BIT,
#ifdef CONFIG_DEBUG_OBJECTS_WORK
        WORK_STRUCT_STATIC      = 1 << WORK_STRUCT_STATIC_BIT,
#else
        WORK_STRUCT_STATIC      = 0,
#endif

        /*
         * The last color is no color used for works which don't
         * participate in workqueue flushing.
         */
        WORK_NR_COLORS          = (1 << WORK_STRUCT_COLOR_BITS) - 1,
        WORK_NO_COLOR           = WORK_NR_COLORS,

        /* not bound to any CPU, prefer the local CPU */
        WORK_CPU_UNBOUND        = NR_CPUS,

        /*
         * Reserve 7 bits off of pwq pointer w/ debugobjects turned off.
         * This makes pwqs aligned to 256 bytes and allows 15 workqueue
         * flush colors.
         */
        WORK_STRUCT_FLAG_BITS   = WORK_STRUCT_COLOR_SHIFT +
                                  WORK_STRUCT_COLOR_BITS,

        /* data contains off-queue information when !WORK_STRUCT_PWQ */
        WORK_OFFQ_FLAG_BASE     = WORK_STRUCT_COLOR_SHIFT,

        __WORK_OFFQ_CANCELING   = WORK_OFFQ_FLAG_BASE,
        WORK_OFFQ_CANCELING     = (1 << __WORK_OFFQ_CANCELING),

        /*
         * When a work item is off queue, its high bits point to the last
         * pool it was on.  Cap at 31 bits and use the highest number to
         * indicate that no pool is associated.
         */
        WORK_OFFQ_FLAG_BITS     = 1,
        WORK_OFFQ_POOL_SHIFT    = WORK_OFFQ_FLAG_BASE + WORK_OFFQ_FLAG_BITS,
        WORK_OFFQ_LEFT          = BITS_PER_LONG - WORK_OFFQ_POOL_SHIFT,
        WORK_OFFQ_POOL_BITS     = WORK_OFFQ_LEFT <= 31 ? WORK_OFFQ_LEFT : 31,
        WORK_OFFQ_POOL_NONE     = (1LU << WORK_OFFQ_POOL_BITS) - 1,

        /* convenience constants */
        WORK_STRUCT_FLAG_MASK   = (1UL << WORK_STRUCT_FLAG_BITS) - 1,
        WORK_STRUCT_WQ_DATA_MASK = ~WORK_STRUCT_FLAG_MASK,
        WORK_STRUCT_NO_POOL     = (unsigned long)WORK_OFFQ_POOL_NONE << WORK_OFFQ_POOL_SHIFT,

        /* bit mask for work_busy() return values */
        WORK_BUSY_PENDING       = 1 << 0,
        WORK_BUSY_RUNNING       = 1 << 1,

        /* maximum string length for set_worker_desc() */
        WORKER_DESC_LEN         = 24,
};

struct work_struct {
        atomic_long_t data;
        struct list_head entry;
        work_func_t func;
#ifdef CONFIG_LOCKDEP
        struct lockdep_map lockdep_map;
#endif
};

#define WORK_DATA_INIT()        ATOMIC_LONG_INIT((unsigned long)WORK_STRUCT_NO_POOL)
#define WORK_DATA_STATIC_INIT() \
        ATOMIC_LONG_INIT((unsigned long)(WORK_STRUCT_NO_POOL | WORK_STRUCT_STATIC))

struct delayed_work {
        struct work_struct work;
        struct timer_list timer;

        /* target workqueue and CPU ->timer uses to queue ->work */
        struct workqueue_struct *wq;
        int cpu;
};

/**
 * struct workqueue_attrs - A struct for workqueue attributes.
 *
 * This can be used to change attributes of an unbound workqueue.
 */
struct workqueue_attrs {
        /**
         * @nice: nice level
         */
        int nice;

        /**
         * @cpumask: allowed CPUs
         */
        cpumask_var_t cpumask;

        /**
         * @no_numa: disable NUMA affinity
         *
         * Unlike other fields, ``no_numa`` isn't a property of a worker_pool. It
         * only modifies how :c:func:`apply_workqueue_attrs` select pools and thus
         * doesn't participate in pool hash calculations or equality comparisons.
         */
        bool no_numa;
};

static inline struct delayed_work *to_delayed_work(struct work_struct *work)
{
        return container_of(work, struct delayed_work, work);
}

struct execute_work {
        struct work_struct work;
};

#ifdef CONFIG_LOCKDEP
/*
 * NB: because we have to copy the lockdep_map, setting _key
 * here is required, otherwise it could get initialised to the
 * copy of the lockdep_map!
 */
#define __WORK_INIT_LOCKDEP_MAP(n, k) \
        .lockdep_map = STATIC_LOCKDEP_MAP_INIT(n, k),
#else
#define __WORK_INIT_LOCKDEP_MAP(n, k)
#endif

#define __WORK_INITIALIZER(n, f) {                                      \
        .data = WORK_DATA_STATIC_INIT(),                                \
        .entry  = { &(n).entry, &(n).entry },                           \
        .func = (f),                                                    \
        __WORK_INIT_LOCKDEP_MAP(#n, &(n))                               \
        }

#define __DELAYED_WORK_INITIALIZER(n, f, tflags) {                      \
        .work = __WORK_INITIALIZER((n).work, (f)),                      \
        .timer = __TIMER_INITIALIZER((TIMER_FUNC_TYPE)delayed_work_timer_fn,\
                                     (TIMER_DATA_TYPE)&(n.timer),       \
                                     (tflags) | TIMER_IRQSAFE),         \
        }

#define DECLARE_WORK(n, f)                                              \
        struct work_struct n = __WORK_INITIALIZER(n, f)

#define DECLARE_DELAYED_WORK(n, f)                                      \
        struct delayed_work n = __DELAYED_WORK_INITIALIZER(n, f, 0)

#define DECLARE_DEFERRABLE_WORK(n, f)                                   \
        struct delayed_work n = __DELAYED_WORK_INITIALIZER(n, f, TIMER_DEFERRABLE)

#ifdef CONFIG_DEBUG_OBJECTS_WORK
extern void __init_work(struct work_struct *work, int onstack);
extern void destroy_work_on_stack(struct work_struct *work);
extern void destroy_delayed_work_on_stack(struct delayed_work *work);
static inline unsigned int work_static(struct work_struct *work)
{
        return *work_data_bits(work) & WORK_STRUCT_STATIC;
}
#else
static inline void __init_work(struct work_struct *work, int onstack) { }
static inline void destroy_work_on_stack(struct work_struct *work) { }
static inline void destroy_delayed_work_on_stack(struct delayed_work *work) { }
static inline unsigned int work_static(struct work_struct *work) { return 0; }
#endif

/*
 * initialize all of a work item in one go
 *
 * NOTE! No point in using "atomic_long_set()": using a direct
 * assignment of the work data initializer allows the compiler
 * to generate better code.
 */
#ifdef CONFIG_LOCKDEP
#define __INIT_WORK(_work, _func, _onstack)                             \
        do {                                                            \
                static struct lock_class_key __key;                     \
                                                                        \
                __init_work((_work), _onstack);                         \
                (_work)->data = (atomic_long_t) WORK_DATA_INIT();       \
                lockdep_init_map(&(_work)->lockdep_map, "(work_completion)"#_work, &__key, 0); \
                INIT_LIST_HEAD(&(_work)->entry);                        \
                (_work)->func = (_func);                                \
        } while (0)
#else
#define __INIT_WORK(_work, _func, _onstack)                             \
        do {                                                            \
                __init_work((_work), _onstack);                         \
                (_work)->data = (atomic_long_t) WORK_DATA_INIT();       \
                INIT_LIST_HEAD(&(_work)->entry);                        \
                (_work)->func = (_func);                                \
        } while (0)
#endif

#define INIT_WORK(_work, _func)                                         \
        __INIT_WORK((_work), (_func), 0)

#define INIT_WORK_ONSTACK(_work, _func)                                 \
        __INIT_WORK((_work), (_func), 1)

#define __INIT_DELAYED_WORK(_work, _func, _tflags)                      \
        do {                                                            \
                INIT_WORK(&(_work)->work, (_func));                     \
                __setup_timer(&(_work)->timer,                          \
                              (TIMER_FUNC_TYPE)delayed_work_timer_fn,   \
                              (TIMER_DATA_TYPE)&(_work)->timer,         \
                              (_tflags) | TIMER_IRQSAFE);               \
        } while (0)

#define __INIT_DELAYED_WORK_ONSTACK(_work, _func, _tflags)              \
        do {                                                            \
                INIT_WORK_ONSTACK(&(_work)->work, (_func));             \
                __setup_timer_on_stack(&(_work)->timer,                 \
                                       (TIMER_FUNC_TYPE)delayed_work_timer_fn,\
                                       (TIMER_DATA_TYPE)&(_work)->timer,\
                                       (_tflags) | TIMER_IRQSAFE);      \
        } while (0)

#define INIT_DELAYED_WORK(_work, _func)                                 \
        __INIT_DELAYED_WORK(_work, _func, 0)

#define INIT_DELAYED_WORK_ONSTACK(_work, _func)                         \
        __INIT_DELAYED_WORK_ONSTACK(_work, _func, 0)

#define INIT_DEFERRABLE_WORK(_work, _func)                              \
        __INIT_DELAYED_WORK(_work, _func, TIMER_DEFERRABLE)

#define INIT_DEFERRABLE_WORK_ONSTACK(_work, _func)                      \
        __INIT_DELAYED_WORK_ONSTACK(_work, _func, TIMER_DEFERRABLE)

/**
 * work_pending - Find out whether a work item is currently pending
 * @work: The work item in question
 */
#define work_pending(work) \
        test_bit(WORK_STRUCT_PENDING_BIT, work_data_bits(work))

/**
 * delayed_work_pending - Find out whether a delayable work item is currently
 * pending
 * @w: The work item in question
 */
#define delayed_work_pending(w) \
        work_pending(&(w)->work)

/*
 * Workqueue flags and constants.  For details, please refer to
 * Documentation/core-api/workqueue.rst.
 */
enum {
        WQ_UNBOUND              = 1 << 1, /* not bound to any cpu */
        WQ_FREEZABLE            = 1 << 2, /* freeze during suspend */
        WQ_MEM_RECLAIM          = 1 << 3, /* may be used for memory reclaim */
        WQ_HIGHPRI              = 1 << 4, /* high priority */
        WQ_CPU_INTENSIVE        = 1 << 5, /* cpu intensive workqueue */
        WQ_SYSFS                = 1 << 6, /* visible in sysfs, see wq_sysfs_register() */

        /*
         * Per-cpu workqueues are generally preferred because they tend to
         * show better performance thanks to cache locality.  Per-cpu
         * workqueues exclude the scheduler from choosing the CPU to
         * execute the worker threads, which has an unfortunate side effect
         * of increasing power consumption.
         *
         * The scheduler considers a CPU idle if it doesn't have any task
         * to execute and tries to keep idle cores idle to conserve power;
         * however, for example, a per-cpu work item scheduled from an
         * interrupt handler on an idle CPU will force the scheduler to
         * excute the work item on that CPU breaking the idleness, which in
         * turn may lead to more scheduling choices which are sub-optimal
         * in terms of power consumption.
         *
         * Workqueues marked with WQ_POWER_EFFICIENT are per-cpu by default
         * but become unbound if workqueue.power_efficient kernel param is
         * specified.  Per-cpu workqueues which are identified to
         * contribute significantly to power-consumption are identified and
         * marked with this flag and enabling the power_efficient mode
         * leads to noticeable power saving at the cost of small
         * performance disadvantage.
         *
         * http://thread.gmane.org/gmane.linux.kernel/1480396
         */
        WQ_POWER_EFFICIENT      = 1 << 7,

        __WQ_DRAINING           = 1 << 16, /* internal: workqueue is draining */
        __WQ_ORDERED            = 1 << 17, /* internal: workqueue is ordered */
        __WQ_LEGACY             = 1 << 18, /* internal: create*_workqueue() */
        __WQ_ORDERED_EXPLICIT   = 1 << 19, /* internal: alloc_ordered_workqueue() */

        WQ_MAX_ACTIVE           = 512,    /* I like 512, better ideas? */
        WQ_MAX_UNBOUND_PER_CPU  = 4,      /* 4 * #cpus for unbound wq */
        WQ_DFL_ACTIVE           = WQ_MAX_ACTIVE / 2,
};

/* unbound wq's aren't per-cpu, scale max_active according to #cpus */
#define WQ_UNBOUND_MAX_ACTIVE   \
        max_t(int, WQ_MAX_ACTIVE, num_possible_cpus() * WQ_MAX_UNBOUND_PER_CPU)

/*
 * System-wide workqueues which are always present.
 *
 * system_wq is the one used by schedule[_delayed]_work[_on]().
 * Multi-CPU multi-threaded.  There are users which expect relatively
 * short queue flush time.  Don't queue works which can run for too
 * long.
 *
 * system_highpri_wq is similar to system_wq but for work items which
 * require WQ_HIGHPRI.
 *
 * system_long_wq is similar to system_wq but may host long running
 * works.  Queue flushing might take relatively long.
 *
 * system_unbound_wq is unbound workqueue.  Workers are not bound to
 * any specific CPU, not concurrency managed, and all queued works are
 * executed immediately as long as max_active limit is not reached and
 * resources are available.
 *
 * system_freezable_wq is equivalent to system_wq except that it's
 * freezable.
 *
 * *_power_efficient_wq are inclined towards saving power and converted
 * into WQ_UNBOUND variants if 'wq_power_efficient' is enabled; otherwise,
 * they are same as their non-power-efficient counterparts - e.g.
 * system_power_efficient_wq is identical to system_wq if
 * 'wq_power_efficient' is disabled.  See WQ_POWER_EFFICIENT for more info.
 */
extern struct workqueue_struct *system_wq;
extern struct workqueue_struct *system_highpri_wq;
extern struct workqueue_struct *system_long_wq;
extern struct workqueue_struct *system_unbound_wq;
extern struct workqueue_struct *system_freezable_wq;
extern struct workqueue_struct *system_power_efficient_wq;
extern struct workqueue_struct *system_freezable_power_efficient_wq;

extern struct workqueue_struct *
__alloc_workqueue_key(const char *fmt, unsigned int flags, int max_active,
        struct lock_class_key *key, const char *lock_name, ...) __printf(1, 6);

/**
 * alloc_workqueue - allocate a workqueue
 * @fmt: printf format for the name of the workqueue
 * @flags: WQ_* flags
 * @max_active: max in-flight work items, 0 for default
 * @args...: args for @fmt
 *
 * Allocate a workqueue with the specified parameters.  For detailed
 * information on WQ_* flags, please refer to
 * Documentation/core-api/workqueue.rst.
 *
 * The __lock_name macro dance is to guarantee that single lock_class_key
 * doesn't end up with different namesm, which isn't allowed by lockdep.
 *
 * RETURNS:
 * Pointer to the allocated workqueue on success, %NULL on failure.
 */
#ifdef CONFIG_LOCKDEP
#define alloc_workqueue(fmt, flags, max_active, args...)                \
({                                                                      \
        static struct lock_class_key __key;                             \
        const char *__lock_name;                                        \
                                                                        \
        __lock_name = "(wq_completion)"#fmt#args;                       \
                                                                        \
        __alloc_workqueue_key((fmt), (flags), (max_active),             \
                              &__key, __lock_name, ##args);             \
})
#else
#define alloc_workqueue(fmt, flags, max_active, args...)                \
        __alloc_workqueue_key((fmt), (flags), (max_active),             \
                              NULL, NULL, ##args)
#endif

/**
 * alloc_ordered_workqueue - allocate an ordered workqueue
 * @fmt: printf format for the name of the workqueue
 * @flags: WQ_* flags (only WQ_FREEZABLE and WQ_MEM_RECLAIM are meaningful)
 * @args...: args for @fmt
 *
 * Allocate an ordered workqueue.  An ordered workqueue executes at
 * most one work item at any given time in the queued order.  They are
 * implemented as unbound workqueues with @max_active of one.
 *
 * RETURNS:
 * Pointer to the allocated workqueue on success, %NULL on failure.
 */
#define alloc_ordered_workqueue(fmt, flags, args...)                    \
        alloc_workqueue(fmt, WQ_UNBOUND | __WQ_ORDERED |                \
                        __WQ_ORDERED_EXPLICIT | (flags), 1, ##args)

#define create_workqueue(name)                                          \
        alloc_workqueue("%s", __WQ_LEGACY | WQ_MEM_RECLAIM, 1, (name))
#define create_freezable_workqueue(name)                                \
        alloc_workqueue("%s", __WQ_LEGACY | WQ_FREEZABLE | WQ_UNBOUND | \
                        WQ_MEM_RECLAIM, 1, (name))
#define create_singlethread_workqueue(name)                             \
        alloc_ordered_workqueue("%s", __WQ_LEGACY | WQ_MEM_RECLAIM, name)

extern void destroy_workqueue(struct workqueue_struct *wq);

struct workqueue_attrs *alloc_workqueue_attrs(gfp_t gfp_mask);
void free_workqueue_attrs(struct workqueue_attrs *attrs);
int apply_workqueue_attrs(struct workqueue_struct *wq,
                          const struct workqueue_attrs *attrs);
int workqueue_set_unbound_cpumask(cpumask_var_t cpumask);

extern bool queue_work_on(int cpu, struct workqueue_struct *wq,
                        struct work_struct *work);
extern bool queue_delayed_work_on(int cpu, struct workqueue_struct *wq,
                        struct delayed_work *work, unsigned long delay);
extern bool mod_delayed_work_on(int cpu, struct workqueue_struct *wq,
                        struct delayed_work *dwork, unsigned long delay);

extern void flush_workqueue(struct workqueue_struct *wq);
extern void drain_workqueue(struct workqueue_struct *wq);

extern int schedule_on_each_cpu(work_func_t func);

int execute_in_process_context(work_func_t fn, struct execute_work *);

extern bool flush_work(struct work_struct *work);
extern bool cancel_work(struct work_struct *work);
extern bool cancel_work_sync(struct work_struct *work);

extern bool flush_delayed_work(struct delayed_work *dwork);
extern bool cancel_delayed_work(struct delayed_work *dwork);
extern bool cancel_delayed_work_sync(struct delayed_work *dwork);

extern void workqueue_set_max_active(struct workqueue_struct *wq,
                                     int max_active);
extern bool current_is_workqueue_rescuer(void);
extern bool workqueue_congested(int cpu, struct workqueue_struct *wq);
extern unsigned int work_busy(struct work_struct *work);
extern __printf(1, 2) void set_worker_desc(const char *fmt, ...);
extern void print_worker_info(const char *log_lvl, struct task_struct *task);
extern void show_workqueue_state(void);

/**
 * queue_work - queue work on a workqueue
 * @wq: workqueue to use
 * @work: work to queue
 *
 * Returns %false if @work was already on a queue, %true otherwise.
 *
 * We queue the work to the CPU on which it was submitted, but if the CPU dies
 * it can be processed by another CPU.
 */
static inline bool queue_work(struct workqueue_struct *wq,
                              struct work_struct *work)
{
        return queue_work_on(WORK_CPU_UNBOUND, wq, work);
}

/**
 * queue_delayed_work - queue work on a workqueue after delay
 * @wq: workqueue to use
 * @dwork: delayable work to queue
 * @delay: number of jiffies to wait before queueing
 *
 * Equivalent to queue_delayed_work_on() but tries to use the local CPU.
 */
static inline bool queue_delayed_work(struct workqueue_struct *wq,
                                      struct delayed_work *dwork,
                                      unsigned long delay)
{
        return queue_delayed_work_on(WORK_CPU_UNBOUND, wq, dwork, delay);
}

/**
 * mod_delayed_work - modify delay of or queue a delayed work
 * @wq: workqueue to use
 * @dwork: work to queue
 * @delay: number of jiffies to wait before queueing
 *
 * mod_delayed_work_on() on local CPU.
 */
static inline bool mod_delayed_work(struct workqueue_struct *wq,
                                    struct delayed_work *dwork,
                                    unsigned long delay)
{
        return mod_delayed_work_on(WORK_CPU_UNBOUND, wq, dwork, delay);
}

/**
 * schedule_work_on - put work task on a specific cpu
 * @cpu: cpu to put the work task on
 * @work: job to be done
 *
 * This puts a job on a specific cpu
 */
static inline bool schedule_work_on(int cpu, struct work_struct *work)
{
        return queue_work_on(cpu, system_wq, work);
}

/**
 * schedule_work - put work task in global workqueue
 * @work: job to be done
 *
 * Returns %false if @work was already on the kernel-global workqueue and
 * %true otherwise.
 *
 * This puts a job in the kernel-global workqueue if it was not already
 * queued and leaves it in the same position on the kernel-global
 * workqueue otherwise.
 */
static inline bool schedule_work(struct work_struct *work)
{
        return queue_work(system_wq, work);
}

/**
 * flush_scheduled_work - ensure that any scheduled work has run to completion.
 *
 * Forces execution of the kernel-global workqueue and blocks until its
 * completion.
 *
 * Think twice before calling this function!  It's very easy to get into
 * trouble if you don't take great care.  Either of the following situations
 * will lead to deadlock:
 *
 *      One of the work items currently on the workqueue needs to acquire
 *      a lock held by your code or its caller.
 *
 *      Your code is running in the context of a work routine.
 *
 * They will be detected by lockdep when they occur, but the first might not
 * occur very often.  It depends on what work items are on the workqueue and
 * what locks they need, which you have no control over.
 *
 * In most situations flushing the entire workqueue is overkill; you merely
 * need to know that a particular work item isn't queued and isn't running.
 * In such cases you should use cancel_delayed_work_sync() or
 * cancel_work_sync() instead.
 */
static inline void flush_scheduled_work(void)
{
        flush_workqueue(system_wq);
}

/**
 * schedule_delayed_work_on - queue work in global workqueue on CPU after delay
 * @cpu: cpu to use
 * @dwork: job to be done
 * @delay: number of jiffies to wait
 *
 * After waiting for a given time this puts a job in the kernel-global
 * workqueue on the specified CPU.
 */
static inline bool schedule_delayed_work_on(int cpu, struct delayed_work *dwork,
                                            unsigned long delay)
{
        return queue_delayed_work_on(cpu, system_wq, dwork, delay);
}

/**
 * schedule_delayed_work - put work task in global workqueue after delay
 * @dwork: job to be done
 * @delay: number of jiffies to wait or 0 for immediate execution
 *
 * After waiting for a given time this puts a job in the kernel-global
 * workqueue.
 */
static inline bool schedule_delayed_work(struct delayed_work *dwork,
                                         unsigned long delay)
{
        return queue_delayed_work(system_wq, dwork, delay);
}

#ifndef CONFIG_SMP
static inline long work_on_cpu(int cpu, long (*fn)(void *), void *arg)
{
        return fn(arg);
}
static inline long work_on_cpu_safe(int cpu, long (*fn)(void *), void *arg)
{
        return fn(arg);
}
#else
long work_on_cpu(int cpu, long (*fn)(void *), void *arg);
long work_on_cpu_safe(int cpu, long (*fn)(void *), void *arg);
#endif /* CONFIG_SMP */

#ifdef CONFIG_FREEZER
extern void freeze_workqueues_begin(void);
extern bool freeze_workqueues_busy(void);
extern void thaw_workqueues(void);
#endif /* CONFIG_FREEZER */

#ifdef CONFIG_SYSFS
int workqueue_sysfs_register(struct workqueue_struct *wq);
#else   /* CONFIG_SYSFS */
static inline int workqueue_sysfs_register(struct workqueue_struct *wq)
{ return 0; }
#endif  /* CONFIG_SYSFS */

#ifdef CONFIG_WQ_WATCHDOG
void wq_watchdog_touch(int cpu);
#else   /* CONFIG_WQ_WATCHDOG */
static inline void wq_watchdog_touch(int cpu) { }
#endif  /* CONFIG_WQ_WATCHDOG */

#ifdef CONFIG_SMP
int workqueue_prepare_cpu(unsigned int cpu);
int workqueue_online_cpu(unsigned int cpu);
int workqueue_offline_cpu(unsigned int cpu);
#endif

int __init workqueue_init_early(void);
int __init workqueue_init(void);

#endif