[linux-block.git] / drivers / md / bcache / closure.h

#ifndef _LINUX_CLOSURE_H
#define _LINUX_CLOSURE_H

#include <linux/llist.h>
#include <linux/sched.h>
#include <linux/sched/task_stack.h>
#include <linux/workqueue.h>

/*
 * Closure is perhaps the most overused and abused term in computer science, but
 * since I've been unable to come up with anything better you're stuck with it
 * again.
 *
 * What are closures?
 *
 * They embed a refcount. The basic idea is they count "things that are in
 * progress" - in flight bios, some other thread that's doing something else -
 * anything you might want to wait on.
 *
 * The refcount may be manipulated with closure_get() and closure_put().
 * closure_put() is where many of the interesting things happen, when it causes
 * the refcount to go to 0.
 *
 * Closures can be used to wait on things both synchronously and asynchronously,
 * and synchronous and asynchronous use can be mixed without restriction. To
 * wait synchronously, use closure_sync() - you will sleep until your closure's
 * refcount hits 1.
 *
 * To wait asynchronously, use
 *   continue_at(cl, next_function, workqueue);
 *
 * passing it, as you might expect, the function to run when nothing is pending
 * and the workqueue to run that function out of.
 *
 * continue_at() also, critically, requires a 'return' immediately following the
 * location where this macro is referenced, to return to the calling function.
 * There's good reason for this.
 *
 * To use safely closures asynchronously, they must always have a refcount while
 * they are running owned by the thread that is running them. Otherwise, suppose
 * you submit some bios and wish to have a function run when they all complete:
 *
 * foo_endio(struct bio *bio)
 * {
 *	closure_put(cl);
 * }
 *
 * closure_init(cl);
 *
 * do_stuff();
 * closure_get(cl);
 * bio1->bi_endio = foo_endio;
 * bio_submit(bio1);
 *
 * do_more_stuff();
 * closure_get(cl);
 * bio2->bi_endio = foo_endio;
 * bio_submit(bio2);
 *
 * continue_at(cl, complete_some_read, system_wq);
 *
 * If closure's refcount started at 0, complete_some_read() could run before the
 * second bio was submitted - which is almost always not what you want! More
 * importantly, it wouldn't be possible to say whether the original thread or
 * complete_some_read()'s thread owned the closure - and whatever state it was
 * associated with!
 *
 * So, closure_init() initializes a closure's refcount to 1 - and when a
 * closure_fn is run, the refcount will be reset to 1 first.
 *
 * Then, the rule is - if you got the refcount with closure_get(), release it
 * with closure_put() (i.e, in a bio->bi_endio function). If you have a refcount
 * on a closure because you called closure_init() or you were run out of a
 * closure - _always_ use continue_at(). Doing so consistently will help
 * eliminate an entire class of particularly pernicious races.
 *
 * Lastly, you might have a wait list dedicated to a specific event, and have no
 * need for specifying the condition - you just want to wait until someone runs
 * closure_wake_up() on the appropriate wait list. In that case, just use
 * closure_wait(). It will return either true or false, depending on whether the
 * closure was already on a wait list or not - a closure can only be on one wait
 * list at a time.
 *
 * Parents:
 *
 * closure_init() takes two arguments - it takes the closure to initialize, and
 * a (possibly null) parent.
 *
 * If parent is non null, the new closure will have a refcount for its lifetime;
 * a closure is considered to be "finished" when its refcount hits 0 and the
 * function to run is null. Hence
 *
 * continue_at(cl, NULL, NULL);
 *
 * returns up the (spaghetti) stack of closures, precisely like normal return
 * returns up the C stack. continue_at() with non null fn is better thought of
 * as doing a tail call.
 *
 * All this implies that a closure should typically be embedded in a particular
 * struct (which its refcount will normally control the lifetime of), and that
 * struct can very much be thought of as a stack frame.
 */

struct closure;
typedef void (closure_fn) (struct closure *);

struct closure_waitlist {
	struct llist_head	list;
};

enum closure_state {
	/*
	 * CLOSURE_WAITING: Set iff the closure is on a waitlist. Must be set by
	 * the thread that owns the closure, and cleared by the thread that's
	 * waking up the closure.
	 *
	 * CLOSURE_SLEEPING: Must be set before a thread uses a closure to sleep
	 * - indicates that cl->task is valid and closure_put() may wake it up.
	 * Only set or cleared by the thread that owns the closure.
	 *
	 * The rest are for debugging and don't affect behaviour:
	 *
	 * CLOSURE_RUNNING: Set when a closure is running (i.e. by
	 * closure_init() and when closure_put() runs then next function), and
	 * must be cleared before remaining hits 0. Primarily to help guard
	 * against incorrect usage and accidentally transferring references.
	 * continue_at() and closure_return() clear it for you, if you're doing
	 * something unusual you can use closure_set_dead() which also helps
	 * annotate where references are being transferred.
	 *
	 * CLOSURE_STACK: Sanity check - remaining should never hit 0 on a
	 * closure with this flag set
	 */

	CLOSURE_BITS_START	= (1 << 23),
	CLOSURE_DESTRUCTOR	= (1 << 23),
	CLOSURE_WAITING		= (1 << 25),
	CLOSURE_SLEEPING	= (1 << 27),
	CLOSURE_RUNNING		= (1 << 29),
	CLOSURE_STACK		= (1 << 31),
};

#define CLOSURE_GUARD_MASK					\
	((CLOSURE_DESTRUCTOR|CLOSURE_WAITING|CLOSURE_SLEEPING|	\
	  CLOSURE_RUNNING|CLOSURE_STACK) << 1)

#define CLOSURE_REMAINING_MASK		(CLOSURE_BITS_START - 1)
#define CLOSURE_REMAINING_INITIALIZER	(1|CLOSURE_RUNNING)

struct closure {
	union {
		struct {
			struct workqueue_struct *wq;
			struct task_struct	*task;
			struct llist_node	list;
			closure_fn		*fn;
		};
		struct work_struct	work;
	};

	struct closure		*parent;

	atomic_t		remaining;

#ifdef CONFIG_BCACHE_CLOSURES_DEBUG
#define CLOSURE_MAGIC_DEAD	0xc054dead
#define CLOSURE_MAGIC_ALIVE	0xc054a11e

	unsigned		magic;
	struct list_head	all;
	unsigned long		ip;
	unsigned long		waiting_on;
#endif
};

void closure_sub(struct closure *cl, int v);
void closure_put(struct closure *cl);
void __closure_wake_up(struct closure_waitlist *list);
bool closure_wait(struct closure_waitlist *list, struct closure *cl);
void closure_sync(struct closure *cl);

#ifdef CONFIG_BCACHE_CLOSURES_DEBUG

void closure_debug_init(void);
void closure_debug_create(struct closure *cl);
void closure_debug_destroy(struct closure *cl);

#else

static inline void closure_debug_init(void) {}
static inline void closure_debug_create(struct closure *cl) {}
static inline void closure_debug_destroy(struct closure *cl) {}

#endif

static inline void closure_set_ip(struct closure *cl)
{
#ifdef CONFIG_BCACHE_CLOSURES_DEBUG
	cl->ip = _THIS_IP_;
#endif
}

static inline void closure_set_ret_ip(struct closure *cl)
{
#ifdef CONFIG_BCACHE_CLOSURES_DEBUG
	cl->ip = _RET_IP_;
#endif
}

static inline void closure_set_waiting(struct closure *cl, unsigned long f)
{
#ifdef CONFIG_BCACHE_CLOSURES_DEBUG
	cl->waiting_on = f;
#endif
}

static inline void __closure_end_sleep(struct closure *cl)
{
	__set_current_state(TASK_RUNNING);

	if (atomic_read(&cl->remaining) & CLOSURE_SLEEPING)
		atomic_sub(CLOSURE_SLEEPING, &cl->remaining);
}

static inline void __closure_start_sleep(struct closure *cl)
{
	closure_set_ip(cl);
	cl->task = current;
	set_current_state(TASK_UNINTERRUPTIBLE);

	if (!(atomic_read(&cl->remaining) & CLOSURE_SLEEPING))
		atomic_add(CLOSURE_SLEEPING, &cl->remaining);
}

static inline void closure_set_stopped(struct closure *cl)
{
	atomic_sub(CLOSURE_RUNNING, &cl->remaining);
}

static inline void set_closure_fn(struct closure *cl, closure_fn *fn,
				  struct workqueue_struct *wq)
{
	BUG_ON(object_is_on_stack(cl));
	closure_set_ip(cl);
	cl->fn = fn;
	cl->wq = wq;
	/* between atomic_dec() in closure_put() */
	smp_mb__before_atomic();
}

static inline void closure_queue(struct closure *cl)
{
	struct workqueue_struct *wq = cl->wq;
	if (wq) {
		INIT_WORK(&cl->work, cl->work.func);
		BUG_ON(!queue_work(wq, &cl->work));
	} else
		cl->fn(cl);
}

/**
 * closure_get - increment a closure's refcount
 */
static inline void closure_get(struct closure *cl)
{
#ifdef CONFIG_BCACHE_CLOSURES_DEBUG
	BUG_ON((atomic_inc_return(&cl->remaining) &
		CLOSURE_REMAINING_MASK) <= 1);
#else
	atomic_inc(&cl->remaining);
#endif
}

/**
 * closure_init - Initialize a closure, setting the refcount to 1
 * @cl:		closure to initialize
 * @parent:	parent of the new closure. cl will take a refcount on it for its
 *		lifetime; may be NULL.
 */
static inline void closure_init(struct closure *cl, struct closure *parent)
{
	memset(cl, 0, sizeof(struct closure));
	cl->parent = parent;
	if (parent)
		closure_get(parent);

	atomic_set(&cl->remaining, CLOSURE_REMAINING_INITIALIZER);

	closure_debug_create(cl);
	closure_set_ip(cl);
}

static inline void closure_init_stack(struct closure *cl)
{
	memset(cl, 0, sizeof(struct closure));
	atomic_set(&cl->remaining, CLOSURE_REMAINING_INITIALIZER|CLOSURE_STACK);
}

/**
 * closure_wake_up - wake up all closures on a wait list.
 */
static inline void closure_wake_up(struct closure_waitlist *list)
{
	smp_mb();
	__closure_wake_up(list);
}

/**
 * continue_at - jump to another function with barrier
 *
 * After @cl is no longer waiting on anything (i.e. all outstanding refs have
 * been dropped with closure_put()), it will resume execution at @fn running out
 * of @wq (or, if @wq is NULL, @fn will be called by closure_put() directly).
 *
 * NOTE: This macro expands to a return in the calling function!
 *
 * This is because after calling continue_at() you no longer have a ref on @cl,
 * and whatever @cl owns may be freed out from under you - a running closure fn
 * has a ref on its own closure which continue_at() drops.
 */
#define continue_at(_cl, _fn, _wq)					\
do {									\
	set_closure_fn(_cl, _fn, _wq);					\
	closure_sub(_cl, CLOSURE_RUNNING + 1);				\
} while (0)

/**
 * closure_return - finish execution of a closure
 *
 * This is used to indicate that @cl is finished: when all outstanding refs on
 * @cl have been dropped @cl's ref on its parent closure (as passed to
 * closure_init()) will be dropped, if one was specified - thus this can be
 * thought of as returning to the parent closure.
 */
#define closure_return(_cl)	continue_at((_cl), NULL, NULL)

/**
 * continue_at_nobarrier - jump to another function without barrier
 *
 * Causes @fn to be executed out of @cl, in @wq context (or called directly if
 * @wq is NULL).
 *
 * NOTE: like continue_at(), this macro expands to a return in the caller!
 *
 * The ref the caller of continue_at_nobarrier() had on @cl is now owned by @fn,
 * thus it's not safe to touch anything protected by @cl after a
 * continue_at_nobarrier().
 */
#define continue_at_nobarrier(_cl, _fn, _wq)				\
do {									\
	set_closure_fn(_cl, _fn, _wq);					\
	closure_queue(_cl);						\
} while (0)

/**
 * closure_return - finish execution of a closure, with destructor
 *
 * Works like closure_return(), except @destructor will be called when all
 * outstanding refs on @cl have been dropped; @destructor may be used to safely
 * free the memory occupied by @cl, and it is called with the ref on the parent
 * closure still held - so @destructor could safely return an item to a
 * freelist protected by @cl's parent.
 */
#define closure_return_with_destructor(_cl, _destructor)		\
do {									\
	set_closure_fn(_cl, _destructor, NULL);				\
	closure_sub(_cl, CLOSURE_RUNNING - CLOSURE_DESTRUCTOR + 1);	\
} while (0)

/**
 * closure_call - execute @fn out of a new, uninitialized closure
 *
 * Typically used when running out of one closure, and we want to run @fn
 * asynchronously out of a new closure - @parent will then wait for @cl to
 * finish.
 */
static inline void closure_call(struct closure *cl, closure_fn fn,
				struct workqueue_struct *wq,
				struct closure *parent)
{
	closure_init(cl, parent);
	continue_at_nobarrier(cl, fn, wq);
}

#endif /* _LINUX_CLOSURE_H */
Commit	Line	Data
cafe5635 KO	1	#ifndef _LINUX_CLOSURE_H
	2	#define _LINUX_CLOSURE_H
	3
	4	#include <linux/llist.h>
	5	#include <linux/sched.h>
68db0cf1	6	#include <linux/sched/task_stack.h>
cafe5635 KO	7	#include <linux/workqueue.h>
	8
	9	/*
	10	* Closure is perhaps the most overused and abused term in computer science, but
	11	* since I've been unable to come up with anything better you're stuck with it
	12	* again.
	13	*
	14	* What are closures?
	15	*
	16	* They embed a refcount. The basic idea is they count "things that are in
	17	* progress" - in flight bios, some other thread that's doing something else -
	18	* anything you might want to wait on.
	19	*
	20	* The refcount may be manipulated with closure_get() and closure_put().
	21	* closure_put() is where many of the interesting things happen, when it causes
	22	* the refcount to go to 0.
	23	*
	24	* Closures can be used to wait on things both synchronously and asynchronously,
	25	* and synchronous and asynchronous use can be mixed without restriction. To
	26	* wait synchronously, use closure_sync() - you will sleep until your closure's
	27	* refcount hits 1.
	28	*
	29	* To wait asynchronously, use
	30	* continue_at(cl, next_function, workqueue);
	31	*
	32	* passing it, as you might expect, the function to run when nothing is pending
	33	* and the workqueue to run that function out of.
	34	*
7abc70d7 YW	35	* continue_at() also, critically, requires a 'return' immediately following the
7abc70d7 YW	36	* location where this macro is referenced, to return to the calling function.
cafe5635 KO	37	* There's good reason for this.
	38	*
	39	* To use safely closures asynchronously, they must always have a refcount while
	40	* they are running owned by the thread that is running them. Otherwise, suppose
	41	* you submit some bios and wish to have a function run when they all complete:
	42	*
4246a0b6	43	* foo_endio(struct bio *bio)
cafe5635 KO	44	* {
	45	* closure_put(cl);
	46	* }
	47	*
	48	* closure_init(cl);
	49	*
	50	* do_stuff();
	51	* closure_get(cl);
	52	* bio1->bi_endio = foo_endio;
	53	* bio_submit(bio1);
	54	*
	55	* do_more_stuff();
	56	* closure_get(cl);
	57	* bio2->bi_endio = foo_endio;
	58	* bio_submit(bio2);
	59	*
	60	* continue_at(cl, complete_some_read, system_wq);
	61	*
	62	* If closure's refcount started at 0, complete_some_read() could run before the
	63	* second bio was submitted - which is almost always not what you want! More
	64	* importantly, it wouldn't be possible to say whether the original thread or
	65	* complete_some_read()'s thread owned the closure - and whatever state it was
	66	* associated with!
	67	*
	68	* So, closure_init() initializes a closure's refcount to 1 - and when a
	69	* closure_fn is run, the refcount will be reset to 1 first.
	70	*
	71	* Then, the rule is - if you got the refcount with closure_get(), release it
	72	* with closure_put() (i.e, in a bio->bi_endio function). If you have a refcount
	73	* on a closure because you called closure_init() or you were run out of a
	74	* closure - _always_ use continue_at(). Doing so consistently will help
	75	* eliminate an entire class of particularly pernicious races.
	76	*
cafe5635 KO	77	* Lastly, you might have a wait list dedicated to a specific event, and have no
	78	* need for specifying the condition - you just want to wait until someone runs
	79	* closure_wake_up() on the appropriate wait list. In that case, just use
	80	* closure_wait(). It will return either true or false, depending on whether the
	81	* closure was already on a wait list or not - a closure can only be on one wait
	82	* list at a time.
	83	*
	84	* Parents:
	85	*
	86	* closure_init() takes two arguments - it takes the closure to initialize, and
	87	* a (possibly null) parent.
	88	*
	89	* If parent is non null, the new closure will have a refcount for its lifetime;
	90	* a closure is considered to be "finished" when its refcount hits 0 and the
	91	* function to run is null. Hence
	92	*
	93	* continue_at(cl, NULL, NULL);
	94	*
	95	* returns up the (spaghetti) stack of closures, precisely like normal return
	96	* returns up the C stack. continue_at() with non null fn is better thought of
	97	* as doing a tail call.
	98	*
	99	* All this implies that a closure should typically be embedded in a particular
	100	* struct (which its refcount will normally control the lifetime of), and that
	101	* struct can very much be thought of as a stack frame.
cafe5635 KO	102	*/
	103
	104	struct closure;
	105	typedef void (closure_fn) (struct closure *);
	106
	107	struct closure_waitlist {
	108	struct llist_head list;
	109	};
	110
cafe5635 KO	111	enum closure_state {
cafe5635 KO	112	/*
cafe5635 KO	113	* CLOSURE_WAITING: Set iff the closure is on a waitlist. Must be set by
	114	* the thread that owns the closure, and cleared by the thread that's
	115	* waking up the closure.
	116	*
	117	* CLOSURE_SLEEPING: Must be set before a thread uses a closure to sleep
	118	* - indicates that cl->task is valid and closure_put() may wake it up.
	119	* Only set or cleared by the thread that owns the closure.
	120	*
cafe5635 KO	121	* The rest are for debugging and don't affect behaviour:
	122	*
	123	* CLOSURE_RUNNING: Set when a closure is running (i.e. by
	124	* closure_init() and when closure_put() runs then next function), and
	125	* must be cleared before remaining hits 0. Primarily to help guard
	126	* against incorrect usage and accidentally transferring references.
	127	* continue_at() and closure_return() clear it for you, if you're doing
	128	* something unusual you can use closure_set_dead() which also helps
	129	* annotate where references are being transferred.
	130	*
	131	* CLOSURE_STACK: Sanity check - remaining should never hit 0 on a
	132	* closure with this flag set
	133	*/
	134
faadf0c9 KO	135	CLOSURE_BITS_START = (1 << 23),
	136	CLOSURE_DESTRUCTOR = (1 << 23),
	137	CLOSURE_WAITING = (1 << 25),
	138	CLOSURE_SLEEPING = (1 << 27),
cafe5635 KO	139	CLOSURE_RUNNING = (1 << 29),
	140	CLOSURE_STACK = (1 << 31),
	141	};
	142
	143	#define CLOSURE_GUARD_MASK \
faadf0c9 KO	144	((CLOSURE_DESTRUCTOR\|CLOSURE_WAITING\|CLOSURE_SLEEPING\| \
faadf0c9 KO	145	CLOSURE_RUNNING\|CLOSURE_STACK) << 1)
cafe5635 KO	146
	147	#define CLOSURE_REMAINING_MASK (CLOSURE_BITS_START - 1)
	148	#define CLOSURE_REMAINING_INITIALIZER (1\|CLOSURE_RUNNING)
	149
	150	struct closure {
	151	union {
	152	struct {
	153	struct workqueue_struct *wq;
	154	struct task_struct *task;
	155	struct llist_node list;
	156	closure_fn *fn;
	157	};
	158	struct work_struct work;
	159	};
	160
	161	struct closure *parent;
	162
	163	atomic_t remaining;
	164
cafe5635 KO	165	#ifdef CONFIG_BCACHE_CLOSURES_DEBUG
	166	#define CLOSURE_MAGIC_DEAD 0xc054dead
	167	#define CLOSURE_MAGIC_ALIVE 0xc054a11e
	168
	169	unsigned magic;
	170	struct list_head all;
	171	unsigned long ip;
	172	unsigned long waiting_on;
	173	#endif
	174	};
	175
cafe5635 KO	176	void closure_sub(struct closure *cl, int v);
cafe5635 KO	177	void closure_put(struct closure *cl);
cafe5635 KO	178	void __closure_wake_up(struct closure_waitlist *list);
	179	bool closure_wait(struct closure_waitlist list, struct closure cl);
	180	void closure_sync(struct closure *cl);
	181
cafe5635 KO	182	#ifdef CONFIG_BCACHE_CLOSURES_DEBUG
cafe5635 KO	183
07e86ccb	184	void closure_debug_init(void);
cafe5635 KO	185	void closure_debug_create(struct closure *cl);
	186	void closure_debug_destroy(struct closure *cl);
	187
	188	#else
	189
07e86ccb	190	static inline void closure_debug_init(void) {}
cafe5635 KO	191	static inline void closure_debug_create(struct closure *cl) {}
	192	static inline void closure_debug_destroy(struct closure *cl) {}
	193
	194	#endif
	195
	196	static inline void closure_set_ip(struct closure *cl)
	197	{
	198	#ifdef CONFIG_BCACHE_CLOSURES_DEBUG
	199	cl->ip = _THIS_IP_;
	200	#endif
	201	}
	202
	203	static inline void closure_set_ret_ip(struct closure *cl)
	204	{
	205	#ifdef CONFIG_BCACHE_CLOSURES_DEBUG
	206	cl->ip = _RET_IP_;
	207	#endif
	208	}
	209
1dd13c8d	210	static inline void closure_set_waiting(struct closure *cl, unsigned long f)
cafe5635 KO	211	{
cafe5635 KO	212	#ifdef CONFIG_BCACHE_CLOSURES_DEBUG
1dd13c8d	213	cl->waiting_on = f;
cafe5635 KO	214	#endif
	215	}
	216
1dd13c8d KO	217	static inline void __closure_end_sleep(struct closure *cl)
	218	{
	219	__set_current_state(TASK_RUNNING);
	220
	221	if (atomic_read(&cl->remaining) & CLOSURE_SLEEPING)
	222	atomic_sub(CLOSURE_SLEEPING, &cl->remaining);
	223	}
	224
	225	static inline void __closure_start_sleep(struct closure *cl)
	226	{
	227	closure_set_ip(cl);
	228	cl->task = current;
	229	set_current_state(TASK_UNINTERRUPTIBLE);
	230
	231	if (!(atomic_read(&cl->remaining) & CLOSURE_SLEEPING))
	232	atomic_add(CLOSURE_SLEEPING, &cl->remaining);
	233	}
	234
cafe5635 KO	235	static inline void closure_set_stopped(struct closure *cl)
	236	{
	237	atomic_sub(CLOSURE_RUNNING, &cl->remaining);
	238	}
	239
1dd13c8d KO	240	static inline void set_closure_fn(struct closure cl, closure_fn fn,
1dd13c8d KO	241	struct workqueue_struct *wq)
cafe5635	242	{
1dd13c8d KO	243	BUG_ON(object_is_on_stack(cl));
	244	closure_set_ip(cl);
	245	cl->fn = fn;
	246	cl->wq = wq;
	247	/* between atomic_dec() in closure_put() */
4e857c58	248	smp_mb__before_atomic();
cafe5635 KO	249	}
cafe5635 KO	250
1dd13c8d	251	static inline void closure_queue(struct closure *cl)
cafe5635	252	{
1dd13c8d KO	253	struct workqueue_struct *wq = cl->wq;
	254	if (wq) {
	255	INIT_WORK(&cl->work, cl->work.func);
	256	BUG_ON(!queue_work(wq, &cl->work));
cafe5635	257	} else
1dd13c8d	258	cl->fn(cl);
cafe5635 KO	259	}
cafe5635 KO	260
1dd13c8d KO	261	/**
1dd13c8d KO	262	* closure_get - increment a closure's refcount
cafe5635	263	*/
1dd13c8d KO	264	static inline void closure_get(struct closure *cl)
	265	{
	266	#ifdef CONFIG_BCACHE_CLOSURES_DEBUG
	267	BUG_ON((atomic_inc_return(&cl->remaining) &
	268	CLOSURE_REMAINING_MASK) <= 1);
	269	#else
	270	atomic_inc(&cl->remaining);
	271	#endif
	272	}
cafe5635	273
cafe5635	274	/**
1dd13c8d	275	* closure_init - Initialize a closure, setting the refcount to 1
cafe5635 KO	276	* @cl: closure to initialize
	277	* @parent: parent of the new closure. cl will take a refcount on it for its
	278	* lifetime; may be NULL.
	279	*/
1dd13c8d	280	static inline void closure_init(struct closure cl, struct closure parent)
cafe5635 KO	281	{
cafe5635 KO	282	memset(cl, 0, sizeof(struct closure));
1dd13c8d KO	283	cl->parent = parent;
	284	if (parent)
	285	closure_get(parent);
cafe5635	286
1dd13c8d	287	atomic_set(&cl->remaining, CLOSURE_REMAINING_INITIALIZER);
cafe5635	288
1dd13c8d KO	289	closure_debug_create(cl);
1dd13c8d KO	290	closure_set_ip(cl);
cafe5635 KO	291	}
cafe5635 KO	292
1dd13c8d	293	static inline void closure_init_stack(struct closure *cl)
cafe5635	294	{
1dd13c8d KO	295	memset(cl, 0, sizeof(struct closure));
1dd13c8d KO	296	atomic_set(&cl->remaining, CLOSURE_REMAINING_INITIALIZER\|CLOSURE_STACK);
cafe5635 KO	297	}
cafe5635 KO	298
cafe5635	299	/**
1dd13c8d	300	* closure_wake_up - wake up all closures on a wait list.
cafe5635 KO	301	*/
	302	static inline void closure_wake_up(struct closure_waitlist *list)
	303	{
	304	smp_mb();
	305	__closure_wake_up(list);
	306	}
	307
1dd13c8d KO	308	/**
	309	* continue_at - jump to another function with barrier
	310	*
	311	* After @cl is no longer waiting on anything (i.e. all outstanding refs have
	312	* been dropped with closure_put()), it will resume execution at @fn running out
	313	* of @wq (or, if @wq is NULL, @fn will be called by closure_put() directly).
	314	*
	315	* NOTE: This macro expands to a return in the calling function!
	316	*
	317	* This is because after calling continue_at() you no longer have a ref on @cl,
	318	* and whatever @cl owns may be freed out from under you - a running closure fn
	319	* has a ref on its own closure which continue_at() drops.
cafe5635	320	*/
cafe5635 KO	321	#define continue_at(_cl, _fn, _wq) \
	322	do { \
	323	set_closure_fn(_cl, _fn, _wq); \
	324	closure_sub(_cl, CLOSURE_RUNNING + 1); \
cafe5635 KO	325	} while (0)
cafe5635 KO	326
1dd13c8d KO	327	/**
	328	* closure_return - finish execution of a closure
	329	*
	330	* This is used to indicate that @cl is finished: when all outstanding refs on
	331	* @cl have been dropped @cl's ref on its parent closure (as passed to
	332	* closure_init()) will be dropped, if one was specified - thus this can be
	333	* thought of as returning to the parent closure.
	334	*/
cafe5635 KO	335	#define closure_return(_cl) continue_at((_cl), NULL, NULL)
cafe5635 KO	336
1dd13c8d KO	337	/**
	338	* continue_at_nobarrier - jump to another function without barrier
	339	*
	340	* Causes @fn to be executed out of @cl, in @wq context (or called directly if
	341	* @wq is NULL).
	342	*
	343	* NOTE: like continue_at(), this macro expands to a return in the caller!
	344	*
	345	* The ref the caller of continue_at_nobarrier() had on @cl is now owned by @fn,
	346	* thus it's not safe to touch anything protected by @cl after a
	347	* continue_at_nobarrier().
	348	*/
cafe5635 KO	349	#define continue_at_nobarrier(_cl, _fn, _wq) \
	350	do { \
	351	set_closure_fn(_cl, _fn, _wq); \
a34a8bfd	352	closure_queue(_cl); \
cafe5635 KO	353	} while (0)
cafe5635 KO	354
1dd13c8d KO	355	/**
	356	* closure_return - finish execution of a closure, with destructor
	357	*
	358	* Works like closure_return(), except @destructor will be called when all
	359	* outstanding refs on @cl have been dropped; @destructor may be used to safely
	360	* free the memory occupied by @cl, and it is called with the ref on the parent
	361	* closure still held - so @destructor could safely return an item to a
	362	* freelist protected by @cl's parent.
	363	*/
cafe5635 KO	364	#define closure_return_with_destructor(_cl, _destructor) \
	365	do { \
	366	set_closure_fn(_cl, _destructor, NULL); \
	367	closure_sub(_cl, CLOSURE_RUNNING - CLOSURE_DESTRUCTOR + 1); \
cafe5635 KO	368	} while (0)
cafe5635 KO	369
1dd13c8d KO	370	/**
	371	* closure_call - execute @fn out of a new, uninitialized closure
	372	*
	373	* Typically used when running out of one closure, and we want to run @fn
	374	* asynchronously out of a new closure - @parent will then wait for @cl to
	375	* finish.
	376	*/
cafe5635 KO	377	static inline void closure_call(struct closure *cl, closure_fn fn,
	378	struct workqueue_struct *wq,
	379	struct closure *parent)
	380	{
	381	closure_init(cl, parent);
	382	continue_at_nobarrier(cl, fn, wq);
	383	}
	384
cafe5635	385	#endif /* _LINUX_CLOSURE_H */