+++ /dev/null
-/* 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 work_struct *);
-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;
- bool closure_get_happened;
-
-#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)
-{
-#ifdef CONFIG_DEBUG_CLOSURES
- BUG_ON(closure_nr_remaining(cl) != 1 && !cl->closure_get_happened);
-#endif
-
- if (cl->closure_get_happened)
- __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;
-}
-
-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->work);
-}
-
-/**
- * closure_get - increment a closure's refcount
- */
-static inline void closure_get(struct closure *cl)
-{
- cl->closure_get_happened = true;
-
-#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);
- cl->closure_get_happened = false;
-
- 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);
-}
-
-#define CLOSURE_CALLBACK(name) void name(struct work_struct *ws)
-#define closure_type(name, type, member) \
- struct closure *cl = container_of(ws, struct closure, work); \
- type *name = container_of(cl, type, member)
-
-/**
- * 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 */
projects / bcachefs-tools-debian / blobdiff