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Diffstat (limited to 'drivers/md/bcache/closure.h')
| -rw-r--r-- | drivers/md/bcache/closure.h | 378 |
1 files changed, 0 insertions, 378 deletions
diff --git a/drivers/md/bcache/closure.h b/drivers/md/bcache/closure.h deleted file mode 100644 index c88cdc4ae4..0000000000 --- a/drivers/md/bcache/closure.h +++ /dev/null @@ -1,378 +0,0 @@ -/* 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_BCACHE_CLOSURES_DEBUG -#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); - -/** - * 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 ((atomic_read(&cl->remaining) & CLOSURE_REMAINING_MASK) != 1) - __closure_sync(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_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_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_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); -} - -#endif /* _LINUX_CLOSURE_H */ |