diff options
Diffstat (limited to 'drivers/md/bcache/closure.h')
| -rw-r--r-- | drivers/md/bcache/closure.h | 494 |
1 files changed, 104 insertions, 390 deletions
diff --git a/drivers/md/bcache/closure.h b/drivers/md/bcache/closure.h index 00039924ea9..a08e3eeac3c 100644 --- a/drivers/md/bcache/closure.h +++ b/drivers/md/bcache/closure.h @@ -72,30 +72,6 @@ * closure - _always_ use continue_at(). Doing so consistently will help * eliminate an entire class of particularly pernicious races. * - * For a closure to wait on an arbitrary event, we need to introduce waitlists: - * - * struct closure_waitlist list; - * closure_wait_event(list, cl, condition); - * closure_wake_up(wait_list); - * - * These work analagously to wait_event() and wake_up() - except that instead of - * operating on the current thread (for wait_event()) and lists of threads, they - * operate on an explicit closure and lists of closures. - * - * Because it's a closure we can now wait either synchronously or - * asynchronously. closure_wait_event() returns the current value of the - * condition, and if it returned false continue_at() or closure_sync() can be - * used to wait for it to become true. - * - * It's useful for waiting on things when you can't sleep in the context in - * which you must check the condition (perhaps a spinlock held, or you might be - * beneath generic_make_request() - in which case you can't sleep on IO). - * - * closure_wait_event() will wait either synchronously or asynchronously, - * depending on whether the closure is in blocking mode or not. You can pick a - * mode explicitly with closure_wait_event_sync() and - * closure_wait_event_async(), which do just what you might expect. - * * 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 @@ -121,55 +97,6 @@ * 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. - * - * Locking: - * - * Closures are based on work items but they can be thought of as more like - * threads - in that like threads and unlike work items they have a well - * defined lifetime; they are created (with closure_init()) and eventually - * complete after a continue_at(cl, NULL, NULL). - * - * Suppose you've got some larger structure with a closure embedded in it that's - * used for periodically doing garbage collection. You only want one garbage - * collection happening at a time, so the natural thing to do is protect it with - * a lock. However, it's difficult to use a lock protecting a closure correctly - * because the unlock should come after the last continue_to() (additionally, if - * you're using the closure asynchronously a mutex won't work since a mutex has - * to be unlocked by the same process that locked it). - * - * So to make it less error prone and more efficient, we also have the ability - * to use closures as locks: - * - * closure_init_unlocked(); - * closure_trylock(); - * - * That's all we need for trylock() - the last closure_put() implicitly unlocks - * it for you. But for closure_lock(), we also need a wait list: - * - * struct closure_with_waitlist frobnicator_cl; - * - * closure_init_unlocked(&frobnicator_cl); - * closure_lock(&frobnicator_cl); - * - * A closure_with_waitlist embeds a closure and a wait list - much like struct - * delayed_work embeds a work item and a timer_list. The important thing is, use - * it exactly like you would a regular closure and closure_put() will magically - * handle everything for you. - * - * We've got closures that embed timers, too. They're called, appropriately - * enough: - * struct closure_with_timer; - * - * This gives you access to closure_delay(). It takes a refcount for a specified - * number of jiffies - you could then call closure_sync() (for a slightly - * convoluted version of msleep()) or continue_at() - which gives you the same - * effect as using a delayed work item, except you can reuse the work_struct - * already embedded in struct closure. - * - * Lastly, there's struct closure_with_waitlist_and_timer. It does what you - * probably expect, if you happen to need the features of both. (You don't - * really want to know how all this is implemented, but if I've done my job - * right you shouldn't have to care). */ struct closure; @@ -179,19 +106,8 @@ struct closure_waitlist { struct llist_head list; }; -enum closure_type { - TYPE_closure = 0, - TYPE_closure_with_waitlist = 1, - TYPE_closure_with_timer = 2, - TYPE_closure_with_waitlist_and_timer = 3, - MAX_CLOSURE_TYPE = 3, -}; - enum closure_state { /* - * CLOSURE_BLOCKING: Causes closure_wait_event() to block, instead of - * waiting asynchronously - * * 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. @@ -200,10 +116,6 @@ enum closure_state { * - indicates that cl->task is valid and closure_put() may wake it up. * Only set or cleared by the thread that owns the closure. * - * CLOSURE_TIMER: Analagous to CLOSURE_WAITING, indicates that a closure - * has an outstanding timer. Must be set by the thread that owns the - * closure, and cleared by the timer function when the timer goes off. - * * The rest are for debugging and don't affect behaviour: * * CLOSURE_RUNNING: Set when a closure is running (i.e. by @@ -218,19 +130,17 @@ enum closure_state { * closure with this flag set */ - CLOSURE_BITS_START = (1 << 19), - CLOSURE_DESTRUCTOR = (1 << 19), - CLOSURE_BLOCKING = (1 << 21), - CLOSURE_WAITING = (1 << 23), - CLOSURE_SLEEPING = (1 << 25), - CLOSURE_TIMER = (1 << 27), + 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_BLOCKING|CLOSURE_WAITING| \ - CLOSURE_SLEEPING|CLOSURE_TIMER|CLOSURE_RUNNING|CLOSURE_STACK) << 1) + ((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) @@ -250,8 +160,6 @@ struct closure { atomic_t remaining; - enum closure_type type; - #ifdef CONFIG_BCACHE_CLOSURES_DEBUG #define CLOSURE_MAGIC_DEAD 0xc054dead #define CLOSURE_MAGIC_ALIVE 0xc054a11e @@ -263,54 +171,12 @@ struct closure { #endif }; -struct closure_with_waitlist { - struct closure cl; - struct closure_waitlist wait; -}; - -struct closure_with_timer { - struct closure cl; - struct timer_list timer; -}; - -struct closure_with_waitlist_and_timer { - struct closure cl; - struct closure_waitlist wait; - struct timer_list timer; -}; - -extern unsigned invalid_closure_type(void); - -#define __CLOSURE_TYPE(cl, _t) \ - __builtin_types_compatible_p(typeof(cl), struct _t) \ - ? TYPE_ ## _t : \ - -#define __closure_type(cl) \ -( \ - __CLOSURE_TYPE(cl, closure) \ - __CLOSURE_TYPE(cl, closure_with_waitlist) \ - __CLOSURE_TYPE(cl, closure_with_timer) \ - __CLOSURE_TYPE(cl, closure_with_waitlist_and_timer) \ - invalid_closure_type() \ -) - void closure_sub(struct closure *cl, int v); void closure_put(struct closure *cl); -void closure_queue(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); -bool closure_trylock(struct closure *cl, struct closure *parent); -void __closure_lock(struct closure *cl, struct closure *parent, - struct closure_waitlist *wait_list); - -void do_closure_timer_init(struct closure *cl); -bool __closure_delay(struct closure *cl, unsigned long delay, - struct timer_list *timer); -void __closure_flush(struct closure *cl, struct timer_list *timer); -void __closure_flush_sync(struct closure *cl, struct timer_list *timer); - #ifdef CONFIG_BCACHE_CLOSURES_DEBUG void closure_debug_init(void); @@ -339,200 +205,97 @@ static inline void closure_set_ret_ip(struct closure *cl) #endif } -static inline void closure_get(struct closure *cl) +static inline void closure_set_waiting(struct closure *cl, unsigned long f) { #ifdef CONFIG_BCACHE_CLOSURES_DEBUG - BUG_ON((atomic_inc_return(&cl->remaining) & - CLOSURE_REMAINING_MASK) <= 1); -#else - atomic_inc(&cl->remaining); + cl->waiting_on = f; #endif } -static inline void closure_set_stopped(struct closure *cl) +static inline void __closure_end_sleep(struct closure *cl) { - atomic_sub(CLOSURE_RUNNING, &cl->remaining); + __set_current_state(TASK_RUNNING); + + if (atomic_read(&cl->remaining) & CLOSURE_SLEEPING) + atomic_sub(CLOSURE_SLEEPING, &cl->remaining); } -static inline bool closure_is_stopped(struct closure *cl) +static inline void __closure_start_sleep(struct closure *cl) { - return !(atomic_read(&cl->remaining) & CLOSURE_RUNNING); + 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 bool closure_is_unlocked(struct closure *cl) +static inline void closure_set_stopped(struct closure *cl) { - return atomic_read(&cl->remaining) == -1; + atomic_sub(CLOSURE_RUNNING, &cl->remaining); } -static inline void do_closure_init(struct closure *cl, struct closure *parent, - bool running) +static inline void set_closure_fn(struct closure *cl, closure_fn *fn, + struct workqueue_struct *wq) { - switch (cl->type) { - case TYPE_closure_with_timer: - case TYPE_closure_with_waitlist_and_timer: - do_closure_timer_init(cl); - default: - break; - } - - cl->parent = parent; - if (parent) - closure_get(parent); - - if (running) { - closure_debug_create(cl); - atomic_set(&cl->remaining, CLOSURE_REMAINING_INITIALIZER); - } else - atomic_set(&cl->remaining, -1); - + 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(); } -/* - * Hack to get at the embedded closure if there is one, by doing an unsafe cast: - * the result of __closure_type() is thrown away, it's used merely for type - * checking. - */ -#define __to_internal_closure(cl) \ -({ \ - BUILD_BUG_ON(__closure_type(*cl) > MAX_CLOSURE_TYPE); \ - (struct closure *) cl; \ -}) - -#define closure_init_type(cl, parent, running) \ -do { \ - struct closure *_cl = __to_internal_closure(cl); \ - _cl->type = __closure_type(*(cl)); \ - do_closure_init(_cl, parent, running); \ -} while (0) +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_init() - Initialize a closure, skipping the memset() - * - * May be used instead of closure_init() when memory has already been zeroed. + * closure_get - increment a closure's refcount */ -#define __closure_init(cl, parent) \ - closure_init_type(cl, parent, true) +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 + * 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. */ -#define closure_init(cl, parent) \ -do { \ - memset((cl), 0, sizeof(*(cl))); \ - __closure_init(cl, parent); \ -} while (0) - -static inline void closure_init_stack(struct closure *cl) +static inline void closure_init(struct closure *cl, struct closure *parent) { memset(cl, 0, sizeof(struct closure)); - atomic_set(&cl->remaining, CLOSURE_REMAINING_INITIALIZER| - CLOSURE_BLOCKING|CLOSURE_STACK); -} - -/** - * closure_init_unlocked() - Initialize a closure but leave it unlocked. - * @cl: closure to initialize - * - * For when the closure will be used as a lock. The closure may not be used - * until after a closure_lock() or closure_trylock(). - */ -#define closure_init_unlocked(cl) \ -do { \ - memset((cl), 0, sizeof(*(cl))); \ - closure_init_type(cl, NULL, false); \ -} while (0) - -/** - * closure_lock() - lock and initialize a closure. - * @cl: the closure to lock - * @parent: the new parent for this closure - * - * The closure must be of one of the types that has a waitlist (otherwise we - * wouldn't be able to sleep on contention). - * - * @parent has exactly the same meaning as in closure_init(); if non null, the - * closure will take a reference on @parent which will be released when it is - * unlocked. - */ -#define closure_lock(cl, parent) \ - __closure_lock(__to_internal_closure(cl), parent, &(cl)->wait) - -/** - * closure_delay() - delay some number of jiffies - * @cl: the closure that will sleep - * @delay: the delay in jiffies - * - * Takes a refcount on @cl which will be released after @delay jiffies; this may - * be used to have a function run after a delay with continue_at(), or - * closure_sync() may be used for a convoluted version of msleep(). - */ -#define closure_delay(cl, delay) \ - __closure_delay(__to_internal_closure(cl), delay, &(cl)->timer) - -#define closure_flush(cl) \ - __closure_flush(__to_internal_closure(cl), &(cl)->timer) - -#define closure_flush_sync(cl) \ - __closure_flush_sync(__to_internal_closure(cl), &(cl)->timer) - -static inline void __closure_end_sleep(struct closure *cl) -{ - __set_current_state(TASK_RUNNING); + cl->parent = parent; + if (parent) + closure_get(parent); - if (atomic_read(&cl->remaining) & CLOSURE_SLEEPING) - atomic_sub(CLOSURE_SLEEPING, &cl->remaining); -} + atomic_set(&cl->remaining, CLOSURE_REMAINING_INITIALIZER); -static inline void __closure_start_sleep(struct closure *cl) -{ + closure_debug_create(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); -} - -/** - * closure_blocking() - returns true if the closure is in blocking mode. - * - * If a closure is in blocking mode, closure_wait_event() will sleep until the - * condition is true instead of waiting asynchronously. - */ -static inline bool closure_blocking(struct closure *cl) -{ - return atomic_read(&cl->remaining) & CLOSURE_BLOCKING; -} - -/** - * set_closure_blocking() - put a closure in blocking mode. - * - * If a closure is in blocking mode, closure_wait_event() will sleep until the - * condition is true instead of waiting asynchronously. - * - * Not thread safe - can only be called by the thread running the closure. - */ -static inline void set_closure_blocking(struct closure *cl) -{ - if (!closure_blocking(cl)) - atomic_add(CLOSURE_BLOCKING, &cl->remaining); } -/* - * Not thread safe - can only be called by the thread running the closure. - */ -static inline void clear_closure_blocking(struct closure *cl) +static inline void closure_init_stack(struct closure *cl) { - if (closure_blocking(cl)) - atomic_sub(CLOSURE_BLOCKING, &cl->remaining); + 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. + * closure_wake_up - wake up all closures on a wait list. */ static inline void closure_wake_up(struct closure_waitlist *list) { @@ -540,96 +303,19 @@ static inline void closure_wake_up(struct closure_waitlist *list) __closure_wake_up(list); } -/* - * Wait on an event, synchronously or asynchronously - analogous to wait_event() - * but for closures. - * - * The loop is oddly structured so as to avoid a race; we must check the - * condition again after we've added ourself to the waitlist. We know if we were - * already on the waitlist because closure_wait() returns false; thus, we only - * schedule or break if closure_wait() returns false. If it returns true, we - * just loop again - rechecking the condition. - * - * The __closure_wake_up() is necessary because we may race with the event - * becoming true; i.e. we see event false -> wait -> recheck condition, but the - * thread that made the event true may have called closure_wake_up() before we - * added ourself to the wait list. - * - * We have to call closure_sync() at the end instead of just - * __closure_end_sleep() because a different thread might've called - * closure_wake_up() before us and gotten preempted before they dropped the - * refcount on our closure. If this was a stack allocated closure, that would be - * bad. - */ -#define __closure_wait_event(list, cl, condition, _block) \ -({ \ - bool block = _block; \ - typeof(condition) ret; \ - \ - while (1) { \ - ret = (condition); \ - if (ret) { \ - __closure_wake_up(list); \ - if (block) \ - closure_sync(cl); \ - \ - break; \ - } \ - \ - if (block) \ - __closure_start_sleep(cl); \ - \ - if (!closure_wait(list, cl)) { \ - if (!block) \ - break; \ - \ - schedule(); \ - } \ - } \ - \ - ret; \ -}) - /** - * closure_wait_event() - wait on a condition, synchronously or asynchronously. - * @list: the wait list to wait on - * @cl: the closure that is doing the waiting - * @condition: a C expression for the event to wait for - * - * If the closure is in blocking mode, sleeps until the @condition evaluates to - * true - exactly like wait_event(). + * continue_at - jump to another function with barrier * - * If the closure is not in blocking mode, waits asynchronously; if the - * condition is currently false the @cl is put onto @list and returns. @list - * owns a refcount on @cl; closure_sync() or continue_at() may be used later to - * wait for another thread to wake up @list, which drops the refcount on @cl. + * 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). * - * Returns the value of @condition; @cl will be on @list iff @condition was - * false. + * NOTE: This macro expands to a return in the calling function! * - * closure_wake_up(@list) must be called after changing any variable that could - * cause @condition to become true. + * 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 closure_wait_event(list, cl, condition) \ - __closure_wait_event(list, cl, condition, closure_blocking(cl)) - -#define closure_wait_event_async(list, cl, condition) \ - __closure_wait_event(list, cl, condition, false) - -#define closure_wait_event_sync(list, cl, condition) \ - __closure_wait_event(list, cl, condition, true) - -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_dec(); -} - #define continue_at(_cl, _fn, _wq) \ do { \ set_closure_fn(_cl, _fn, _wq); \ @@ -637,15 +323,44 @@ do { \ return; \ } 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); \ + closure_queue(_cl); \ return; \ } 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); \ @@ -653,6 +368,13 @@ do { \ return; \ } 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) @@ -661,12 +383,4 @@ static inline void closure_call(struct closure *cl, closure_fn fn, continue_at_nobarrier(cl, fn, wq); } -static inline void closure_trylock_call(struct closure *cl, closure_fn fn, - struct workqueue_struct *wq, - struct closure *parent) -{ - if (closure_trylock(cl, parent)) - continue_at_nobarrier(cl, fn, wq); -} - #endif /* _LINUX_CLOSURE_H */ |