[linux-block.git] / include / linux / closure.h

/* SPDX-License-Identifier: GPL-2.0 */
#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;
struct closure_syncer;
typedef void (closure_fn) (struct closure *);
extern struct dentry *bcache_debug;

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.
	 *
	 * 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_BITS_START	= (1U << 26),
	CLOSURE_DESTRUCTOR	= (1U << 26),
	CLOSURE_WAITING		= (1U << 28),
	CLOSURE_RUNNING		= (1U << 30),
};

#define CLOSURE_GUARD_MASK					\
	((CLOSURE_DESTRUCTOR|CLOSURE_WAITING|CLOSURE_RUNNING) << 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 closure_syncer	*s;
			struct llist_node	list;
			closure_fn		*fn;
		};
		struct work_struct	work;
	};

	struct closure		*parent;

	atomic_t		remaining;

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

	unsigned int		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);

static inline unsigned closure_nr_remaining(struct closure *cl)
{
	return atomic_read(&cl->remaining) & CLOSURE_REMAINING_MASK;
}

/**
 * closure_sync - sleep until a closure a closure has nothing left to wait on
 *
 * Sleeps until the refcount hits 1 - the thread that's running the closure owns
 * the last refcount.
 */
static inline void closure_sync(struct closure *cl)
{
	if (closure_nr_remaining(cl) != 1)
		__closure_sync(cl);
}

#ifdef CONFIG_DEBUG_CLOSURES

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

#else

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_DEBUG_CLOSURES
	cl->ip = _THIS_IP_;
#endif
}

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

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

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)
{
	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;
	/**
	 * Changes made to closure, work_struct, or a couple of other structs
	 * may cause work.func not pointing to the right location.
	 */
	BUILD_BUG_ON(offsetof(struct closure, fn)
		     != offsetof(struct work_struct, func));

	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_DEBUG_CLOSURES
	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)
{
	cl->fn = NULL;
	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_wake_up - wake up all closures on a wait list,
 *		     with memory barrier
 */
static inline void closure_wake_up(struct closure_waitlist *list)
{
	/* Memory barrier for the wait 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).
 *
 * 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.
 *
 * Note you are expected to immediately return after using this macro.
 */
#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).
 *
 * 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_with_destructor - 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);
}

#define __closure_wait_event(waitlist, _cond)				\
do {									\
	struct closure cl;						\
									\
	closure_init_stack(&cl);					\
									\
	while (1) {							\
		closure_wait(waitlist, &cl);				\
		if (_cond)						\
			break;						\
		closure_sync(&cl);					\
	}								\
	closure_wake_up(waitlist);					\
	closure_sync(&cl);						\
} while (0)

#define closure_wait_event(waitlist, _cond)				\
do {									\
	if (!(_cond))							\
		__closure_wait_event(waitlist, _cond);			\
} while (0)

#endif /* _LINUX_CLOSURE_H */
Commit	Line	Data
b2441318	1	/* SPDX-License-Identifier: GPL-2.0 */
cafe5635 KO	2	#ifndef _LINUX_CLOSURE_H
	3	#define _LINUX_CLOSURE_H
	4
	5	#include <linux/llist.h>
	6	#include <linux/sched.h>
68db0cf1	7	#include <linux/sched/task_stack.h>
cafe5635 KO	8	#include <linux/workqueue.h>
	9
	10	/*
	11	* Closure is perhaps the most overused and abused term in computer science, but
	12	* since I've been unable to come up with anything better you're stuck with it
	13	* again.
	14	*
	15	* What are closures?
	16	*
	17	* They embed a refcount. The basic idea is they count "things that are in
	18	* progress" - in flight bios, some other thread that's doing something else -
	19	* anything you might want to wait on.
	20	*
	21	* The refcount may be manipulated with closure_get() and closure_put().
	22	* closure_put() is where many of the interesting things happen, when it causes
	23	* the refcount to go to 0.
	24	*
	25	* Closures can be used to wait on things both synchronously and asynchronously,
	26	* and synchronous and asynchronous use can be mixed without restriction. To
	27	* wait synchronously, use closure_sync() - you will sleep until your closure's
	28	* refcount hits 1.
	29	*
	30	* To wait asynchronously, use
	31	* continue_at(cl, next_function, workqueue);
	32	*
	33	* passing it, as you might expect, the function to run when nothing is pending
	34	* and the workqueue to run that function out of.
	35	*
7abc70d7 YW	36	* continue_at() also, critically, requires a 'return' immediately following the
7abc70d7 YW	37	* location where this macro is referenced, to return to the calling function.
cafe5635 KO	38	* There's good reason for this.
	39	*
	40	* To use safely closures asynchronously, they must always have a refcount while
	41	* they are running owned by the thread that is running them. Otherwise, suppose
	42	* you submit some bios and wish to have a function run when they all complete:
	43	*
4246a0b6	44	* foo_endio(struct bio *bio)
cafe5635 KO	45	* {
	46	* closure_put(cl);
	47	* }
	48	*
	49	* closure_init(cl);
	50	*
	51	* do_stuff();
	52	* closure_get(cl);
	53	* bio1->bi_endio = foo_endio;
	54	* bio_submit(bio1);
	55	*
	56	* do_more_stuff();
	57	* closure_get(cl);
	58	* bio2->bi_endio = foo_endio;
	59	* bio_submit(bio2);
	60	*
	61	* continue_at(cl, complete_some_read, system_wq);
	62	*
	63	* If closure's refcount started at 0, complete_some_read() could run before the
	64	* second bio was submitted - which is almost always not what you want! More
	65	* importantly, it wouldn't be possible to say whether the original thread or
	66	* complete_some_read()'s thread owned the closure - and whatever state it was
	67	* associated with!
	68	*
	69	* So, closure_init() initializes a closure's refcount to 1 - and when a
	70	* closure_fn is run, the refcount will be reset to 1 first.
	71	*
	72	* Then, the rule is - if you got the refcount with closure_get(), release it
	73	* with closure_put() (i.e, in a bio->bi_endio function). If you have a refcount
	74	* on a closure because you called closure_init() or you were run out of a
	75	* closure - _always_ use continue_at(). Doing so consistently will help
	76	* eliminate an entire class of particularly pernicious races.
	77	*
cafe5635 KO	78	* Lastly, you might have a wait list dedicated to a specific event, and have no
	79	* need for specifying the condition - you just want to wait until someone runs
	80	* closure_wake_up() on the appropriate wait list. In that case, just use
	81	* closure_wait(). It will return either true or false, depending on whether the
	82	* closure was already on a wait list or not - a closure can only be on one wait
	83	* list at a time.
	84	*
	85	* Parents:
	86	*
	87	* closure_init() takes two arguments - it takes the closure to initialize, and
	88	* a (possibly null) parent.
	89	*
	90	* If parent is non null, the new closure will have a refcount for its lifetime;
	91	* a closure is considered to be "finished" when its refcount hits 0 and the
	92	* function to run is null. Hence
	93	*
	94	* continue_at(cl, NULL, NULL);
	95	*
	96	* returns up the (spaghetti) stack of closures, precisely like normal return
	97	* returns up the C stack. continue_at() with non null fn is better thought of
	98	* as doing a tail call.
	99	*
	100	* All this implies that a closure should typically be embedded in a particular
	101	* struct (which its refcount will normally control the lifetime of), and that
	102	* struct can very much be thought of as a stack frame.
cafe5635 KO	103	*/
	104
	105	struct closure;
e4bf7919	106	struct closure_syncer;
cafe5635	107	typedef void (closure_fn) (struct closure *);
df2b9431	108	extern struct dentry *bcache_debug;
cafe5635 KO	109
	110	struct closure_waitlist {
	111	struct llist_head list;
	112	};
	113
cafe5635 KO	114	enum closure_state {
cafe5635 KO	115	/*
cafe5635 KO	116	* CLOSURE_WAITING: Set iff the closure is on a waitlist. Must be set by
	117	* the thread that owns the closure, and cleared by the thread that's
	118	* waking up the closure.
	119	*
cafe5635 KO	120	* The rest are for debugging and don't affect behaviour:
	121	*
	122	* CLOSURE_RUNNING: Set when a closure is running (i.e. by
	123	* closure_init() and when closure_put() runs then next function), and
	124	* must be cleared before remaining hits 0. Primarily to help guard
	125	* against incorrect usage and accidentally transferring references.
	126	* continue_at() and closure_return() clear it for you, if you're doing
	127	* something unusual you can use closure_set_dead() which also helps
	128	* annotate where references are being transferred.
cafe5635 KO	129	*/
cafe5635 KO	130
3609c471 ML	131	CLOSURE_BITS_START = (1U << 26),
	132	CLOSURE_DESTRUCTOR = (1U << 26),
	133	CLOSURE_WAITING = (1U << 28),
	134	CLOSURE_RUNNING = (1U << 30),
cafe5635 KO	135	};
	136
	137	#define CLOSURE_GUARD_MASK \
e4bf7919	138	((CLOSURE_DESTRUCTOR\|CLOSURE_WAITING\|CLOSURE_RUNNING) << 1)
cafe5635 KO	139
	140	#define CLOSURE_REMAINING_MASK (CLOSURE_BITS_START - 1)
	141	#define CLOSURE_REMAINING_INITIALIZER (1\|CLOSURE_RUNNING)
	142
	143	struct closure {
	144	union {
	145	struct {
	146	struct workqueue_struct *wq;
e4bf7919	147	struct closure_syncer *s;
cafe5635 KO	148	struct llist_node list;
	149	closure_fn *fn;
	150	};
	151	struct work_struct work;
	152	};
	153
	154	struct closure *parent;
	155
	156	atomic_t remaining;
	157
8c8d2d96	158	#ifdef CONFIG_DEBUG_CLOSURES
cafe5635 KO	159	#define CLOSURE_MAGIC_DEAD 0xc054dead
	160	#define CLOSURE_MAGIC_ALIVE 0xc054a11e
	161
6f10f7d1	162	unsigned int magic;
cafe5635 KO	163	struct list_head all;
	164	unsigned long ip;
	165	unsigned long waiting_on;
	166	#endif
	167	};
	168
cafe5635 KO	169	void closure_sub(struct closure *cl, int v);
cafe5635 KO	170	void closure_put(struct closure *cl);
cafe5635 KO	171	void __closure_wake_up(struct closure_waitlist *list);
cafe5635 KO	172	bool closure_wait(struct closure_waitlist list, struct closure cl);
e4bf7919 KO	173	void __closure_sync(struct closure *cl);
e4bf7919 KO	174
48b79357 KO	175	static inline unsigned closure_nr_remaining(struct closure *cl)
	176	{
	177	return atomic_read(&cl->remaining) & CLOSURE_REMAINING_MASK;
	178	}
	179
e4bf7919 KO	180	/**
	181	* closure_sync - sleep until a closure a closure has nothing left to wait on
	182	*
	183	* Sleeps until the refcount hits 1 - the thread that's running the closure owns
	184	* the last refcount.
	185	*/
	186	static inline void closure_sync(struct closure *cl)
	187	{
48b79357	188	if (closure_nr_remaining(cl) != 1)
e4bf7919 KO	189	__closure_sync(cl);
e4bf7919 KO	190	}
cafe5635	191
8c8d2d96	192	#ifdef CONFIG_DEBUG_CLOSURES
cafe5635 KO	193
	194	void closure_debug_create(struct closure *cl);
	195	void closure_debug_destroy(struct closure *cl);
	196
	197	#else
	198
	199	static inline void closure_debug_create(struct closure *cl) {}
	200	static inline void closure_debug_destroy(struct closure *cl) {}
	201
	202	#endif
	203
	204	static inline void closure_set_ip(struct closure *cl)
	205	{
8c8d2d96	206	#ifdef CONFIG_DEBUG_CLOSURES
cafe5635 KO	207	cl->ip = _THIS_IP_;
	208	#endif
	209	}
	210
	211	static inline void closure_set_ret_ip(struct closure *cl)
	212	{
8c8d2d96	213	#ifdef CONFIG_DEBUG_CLOSURES
cafe5635 KO	214	cl->ip = _RET_IP_;
	215	#endif
	216	}
	217
1dd13c8d	218	static inline void closure_set_waiting(struct closure *cl, unsigned long f)
cafe5635	219	{
8c8d2d96	220	#ifdef CONFIG_DEBUG_CLOSURES
1dd13c8d	221	cl->waiting_on = f;
cafe5635 KO	222	#endif
	223	}
	224
	225	static inline void closure_set_stopped(struct closure *cl)
	226	{
	227	atomic_sub(CLOSURE_RUNNING, &cl->remaining);
	228	}
	229
1dd13c8d KO	230	static inline void set_closure_fn(struct closure cl, closure_fn fn,
1dd13c8d KO	231	struct workqueue_struct *wq)
cafe5635	232	{
1dd13c8d KO	233	closure_set_ip(cl);
	234	cl->fn = fn;
	235	cl->wq = wq;
	236	/* between atomic_dec() in closure_put() */
4e857c58	237	smp_mb__before_atomic();
cafe5635 KO	238	}
cafe5635 KO	239
1dd13c8d	240	static inline void closure_queue(struct closure *cl)
cafe5635	241	{
1dd13c8d	242	struct workqueue_struct *wq = cl->wq;
6446c684 LC	243	/**
	244	* Changes made to closure, work_struct, or a couple of other structs
	245	* may cause work.func not pointing to the right location.
	246	*/
	247	BUILD_BUG_ON(offsetof(struct closure, fn)
	248	!= offsetof(struct work_struct, func));
8c8d2d96	249
1dd13c8d KO	250	if (wq) {
	251	INIT_WORK(&cl->work, cl->work.func);
	252	BUG_ON(!queue_work(wq, &cl->work));
cafe5635	253	} else
1dd13c8d	254	cl->fn(cl);
cafe5635 KO	255	}
cafe5635 KO	256
1dd13c8d KO	257	/**
1dd13c8d KO	258	* closure_get - increment a closure's refcount
cafe5635	259	*/
1dd13c8d KO	260	static inline void closure_get(struct closure *cl)
1dd13c8d KO	261	{
8c8d2d96	262	#ifdef CONFIG_DEBUG_CLOSURES
1dd13c8d KO	263	BUG_ON((atomic_inc_return(&cl->remaining) &
	264	CLOSURE_REMAINING_MASK) <= 1);
	265	#else
	266	atomic_inc(&cl->remaining);
	267	#endif
	268	}
cafe5635	269
cafe5635	270	/**
1dd13c8d	271	* closure_init - Initialize a closure, setting the refcount to 1
cafe5635 KO	272	* @cl: closure to initialize
	273	* @parent: parent of the new closure. cl will take a refcount on it for its
	274	* lifetime; may be NULL.
	275	*/
1dd13c8d	276	static inline void closure_init(struct closure cl, struct closure parent)
cafe5635	277	{
8c8d2d96	278	cl->fn = NULL;
1dd13c8d KO	279	cl->parent = parent;
	280	if (parent)
	281	closure_get(parent);
cafe5635	282
1dd13c8d	283	atomic_set(&cl->remaining, CLOSURE_REMAINING_INITIALIZER);
cafe5635	284
1dd13c8d KO	285	closure_debug_create(cl);
1dd13c8d KO	286	closure_set_ip(cl);
cafe5635 KO	287	}
cafe5635 KO	288
1dd13c8d	289	static inline void closure_init_stack(struct closure *cl)
cafe5635	290	{
1dd13c8d	291	memset(cl, 0, sizeof(struct closure));
e4bf7919	292	atomic_set(&cl->remaining, CLOSURE_REMAINING_INITIALIZER);
cafe5635 KO	293	}
cafe5635 KO	294
cafe5635	295	/**
eb2b3d03 CL	296	* closure_wake_up - wake up all closures on a wait list,
eb2b3d03 CL	297	* with memory barrier
cafe5635 KO	298	*/
	299	static inline void closure_wake_up(struct closure_waitlist *list)
	300	{
eb2b3d03	301	/* Memory barrier for the wait list */
cafe5635 KO	302	smp_mb();
	303	__closure_wake_up(list);
	304	}
	305
1dd13c8d KO	306	/**
	307	* continue_at - jump to another function with barrier
	308	*
	309	* After @cl is no longer waiting on anything (i.e. all outstanding refs have
	310	* been dropped with closure_put()), it will resume execution at @fn running out
	311	* of @wq (or, if @wq is NULL, @fn will be called by closure_put() directly).
	312	*
1dd13c8d KO	313	* This is because after calling continue_at() you no longer have a ref on @cl,
	314	* and whatever @cl owns may be freed out from under you - a running closure fn
	315	* has a ref on its own closure which continue_at() drops.
e4bf7919 KO	316	*
e4bf7919 KO	317	* Note you are expected to immediately return after using this macro.
cafe5635	318	*/
cafe5635 KO	319	#define continue_at(_cl, _fn, _wq) \
	320	do { \
	321	set_closure_fn(_cl, _fn, _wq); \
	322	closure_sub(_cl, CLOSURE_RUNNING + 1); \
cafe5635 KO	323	} while (0)
cafe5635 KO	324
1dd13c8d KO	325	/**
	326	* closure_return - finish execution of a closure
	327	*
	328	* This is used to indicate that @cl is finished: when all outstanding refs on
	329	* @cl have been dropped @cl's ref on its parent closure (as passed to
	330	* closure_init()) will be dropped, if one was specified - thus this can be
	331	* thought of as returning to the parent closure.
	332	*/
cafe5635 KO	333	#define closure_return(_cl) continue_at((_cl), NULL, NULL)
cafe5635 KO	334
1dd13c8d KO	335	/**
	336	* continue_at_nobarrier - jump to another function without barrier
	337	*
	338	* Causes @fn to be executed out of @cl, in @wq context (or called directly if
	339	* @wq is NULL).
	340	*
1dd13c8d KO	341	* The ref the caller of continue_at_nobarrier() had on @cl is now owned by @fn,
	342	* thus it's not safe to touch anything protected by @cl after a
	343	* continue_at_nobarrier().
	344	*/
cafe5635 KO	345	#define continue_at_nobarrier(_cl, _fn, _wq) \
	346	do { \
	347	set_closure_fn(_cl, _fn, _wq); \
a34a8bfd	348	closure_queue(_cl); \
cafe5635 KO	349	} while (0)
cafe5635 KO	350
1dd13c8d	351	/**
4516da42 CL	352	* closure_return_with_destructor - finish execution of a closure,
4516da42 CL	353	* with destructor
1dd13c8d KO	354	*
	355	* Works like closure_return(), except @destructor will be called when all
	356	* outstanding refs on @cl have been dropped; @destructor may be used to safely
	357	* free the memory occupied by @cl, and it is called with the ref on the parent
	358	* closure still held - so @destructor could safely return an item to a
	359	* freelist protected by @cl's parent.
	360	*/
cafe5635 KO	361	#define closure_return_with_destructor(_cl, _destructor) \
	362	do { \
	363	set_closure_fn(_cl, _destructor, NULL); \
	364	closure_sub(_cl, CLOSURE_RUNNING - CLOSURE_DESTRUCTOR + 1); \
cafe5635 KO	365	} while (0)
cafe5635 KO	366
1dd13c8d KO	367	/**
	368	* closure_call - execute @fn out of a new, uninitialized closure
	369	*
	370	* Typically used when running out of one closure, and we want to run @fn
	371	* asynchronously out of a new closure - @parent will then wait for @cl to
	372	* finish.
	373	*/
cafe5635 KO	374	static inline void closure_call(struct closure *cl, closure_fn fn,
	375	struct workqueue_struct *wq,
	376	struct closure *parent)
	377	{
	378	closure_init(cl, parent);
	379	continue_at_nobarrier(cl, fn, wq);
	380	}
	381
ced58fc7 KO	382	#define __closure_wait_event(waitlist, _cond) \
	383	do { \
	384	struct closure cl; \
	385	\
	386	closure_init_stack(&cl); \
	387	\
	388	while (1) { \
	389	closure_wait(waitlist, &cl); \
	390	if (_cond) \
	391	break; \
	392	closure_sync(&cl); \
	393	} \
	394	closure_wake_up(waitlist); \
	395	closure_sync(&cl); \
	396	} while (0)
	397
	398	#define closure_wait_event(waitlist, _cond) \
	399	do { \
	400	if (!(_cond)) \
	401	__closure_wait_event(waitlist, _cond); \
	402	} while (0)
	403
cafe5635	404	#endif /* _LINUX_CLOSURE_H */