Kent Overstreet | cafe563 | 2013-03-23 16:11:31 -0700 | [diff] [blame] | 1 | #ifndef _LINUX_CLOSURE_H |
| 2 | #define _LINUX_CLOSURE_H |
| 3 | |
| 4 | #include <linux/llist.h> |
| 5 | #include <linux/sched.h> |
| 6 | #include <linux/workqueue.h> |
| 7 | |
| 8 | /* |
| 9 | * Closure is perhaps the most overused and abused term in computer science, but |
| 10 | * since I've been unable to come up with anything better you're stuck with it |
| 11 | * again. |
| 12 | * |
| 13 | * What are closures? |
| 14 | * |
| 15 | * They embed a refcount. The basic idea is they count "things that are in |
| 16 | * progress" - in flight bios, some other thread that's doing something else - |
| 17 | * anything you might want to wait on. |
| 18 | * |
| 19 | * The refcount may be manipulated with closure_get() and closure_put(). |
| 20 | * closure_put() is where many of the interesting things happen, when it causes |
| 21 | * the refcount to go to 0. |
| 22 | * |
| 23 | * Closures can be used to wait on things both synchronously and asynchronously, |
| 24 | * and synchronous and asynchronous use can be mixed without restriction. To |
| 25 | * wait synchronously, use closure_sync() - you will sleep until your closure's |
| 26 | * refcount hits 1. |
| 27 | * |
| 28 | * To wait asynchronously, use |
| 29 | * continue_at(cl, next_function, workqueue); |
| 30 | * |
| 31 | * passing it, as you might expect, the function to run when nothing is pending |
| 32 | * and the workqueue to run that function out of. |
| 33 | * |
| 34 | * continue_at() also, critically, is a macro that returns the calling function. |
| 35 | * There's good reason for this. |
| 36 | * |
| 37 | * To use safely closures asynchronously, they must always have a refcount while |
| 38 | * they are running owned by the thread that is running them. Otherwise, suppose |
| 39 | * you submit some bios and wish to have a function run when they all complete: |
| 40 | * |
| 41 | * foo_endio(struct bio *bio, int error) |
| 42 | * { |
| 43 | * closure_put(cl); |
| 44 | * } |
| 45 | * |
| 46 | * closure_init(cl); |
| 47 | * |
| 48 | * do_stuff(); |
| 49 | * closure_get(cl); |
| 50 | * bio1->bi_endio = foo_endio; |
| 51 | * bio_submit(bio1); |
| 52 | * |
| 53 | * do_more_stuff(); |
| 54 | * closure_get(cl); |
| 55 | * bio2->bi_endio = foo_endio; |
| 56 | * bio_submit(bio2); |
| 57 | * |
| 58 | * continue_at(cl, complete_some_read, system_wq); |
| 59 | * |
| 60 | * If closure's refcount started at 0, complete_some_read() could run before the |
| 61 | * second bio was submitted - which is almost always not what you want! More |
| 62 | * importantly, it wouldn't be possible to say whether the original thread or |
| 63 | * complete_some_read()'s thread owned the closure - and whatever state it was |
| 64 | * associated with! |
| 65 | * |
| 66 | * So, closure_init() initializes a closure's refcount to 1 - and when a |
| 67 | * closure_fn is run, the refcount will be reset to 1 first. |
| 68 | * |
| 69 | * Then, the rule is - if you got the refcount with closure_get(), release it |
| 70 | * with closure_put() (i.e, in a bio->bi_endio function). If you have a refcount |
| 71 | * on a closure because you called closure_init() or you were run out of a |
| 72 | * closure - _always_ use continue_at(). Doing so consistently will help |
| 73 | * eliminate an entire class of particularly pernicious races. |
| 74 | * |
| 75 | * For a closure to wait on an arbitrary event, we need to introduce waitlists: |
| 76 | * |
| 77 | * struct closure_waitlist list; |
| 78 | * closure_wait_event(list, cl, condition); |
| 79 | * closure_wake_up(wait_list); |
| 80 | * |
| 81 | * These work analagously to wait_event() and wake_up() - except that instead of |
| 82 | * operating on the current thread (for wait_event()) and lists of threads, they |
| 83 | * operate on an explicit closure and lists of closures. |
| 84 | * |
| 85 | * Because it's a closure we can now wait either synchronously or |
| 86 | * asynchronously. closure_wait_event() returns the current value of the |
| 87 | * condition, and if it returned false continue_at() or closure_sync() can be |
| 88 | * used to wait for it to become true. |
| 89 | * |
| 90 | * It's useful for waiting on things when you can't sleep in the context in |
| 91 | * which you must check the condition (perhaps a spinlock held, or you might be |
| 92 | * beneath generic_make_request() - in which case you can't sleep on IO). |
| 93 | * |
| 94 | * closure_wait_event() will wait either synchronously or asynchronously, |
| 95 | * depending on whether the closure is in blocking mode or not. You can pick a |
| 96 | * mode explicitly with closure_wait_event_sync() and |
| 97 | * closure_wait_event_async(), which do just what you might expect. |
| 98 | * |
| 99 | * Lastly, you might have a wait list dedicated to a specific event, and have no |
| 100 | * need for specifying the condition - you just want to wait until someone runs |
| 101 | * closure_wake_up() on the appropriate wait list. In that case, just use |
| 102 | * closure_wait(). It will return either true or false, depending on whether the |
| 103 | * closure was already on a wait list or not - a closure can only be on one wait |
| 104 | * list at a time. |
| 105 | * |
| 106 | * Parents: |
| 107 | * |
| 108 | * closure_init() takes two arguments - it takes the closure to initialize, and |
| 109 | * a (possibly null) parent. |
| 110 | * |
| 111 | * If parent is non null, the new closure will have a refcount for its lifetime; |
| 112 | * a closure is considered to be "finished" when its refcount hits 0 and the |
| 113 | * function to run is null. Hence |
| 114 | * |
| 115 | * continue_at(cl, NULL, NULL); |
| 116 | * |
| 117 | * returns up the (spaghetti) stack of closures, precisely like normal return |
| 118 | * returns up the C stack. continue_at() with non null fn is better thought of |
| 119 | * as doing a tail call. |
| 120 | * |
| 121 | * All this implies that a closure should typically be embedded in a particular |
| 122 | * struct (which its refcount will normally control the lifetime of), and that |
| 123 | * struct can very much be thought of as a stack frame. |
| 124 | * |
| 125 | * Locking: |
| 126 | * |
| 127 | * Closures are based on work items but they can be thought of as more like |
| 128 | * threads - in that like threads and unlike work items they have a well |
| 129 | * defined lifetime; they are created (with closure_init()) and eventually |
| 130 | * complete after a continue_at(cl, NULL, NULL). |
| 131 | * |
| 132 | * Suppose you've got some larger structure with a closure embedded in it that's |
| 133 | * used for periodically doing garbage collection. You only want one garbage |
| 134 | * collection happening at a time, so the natural thing to do is protect it with |
| 135 | * a lock. However, it's difficult to use a lock protecting a closure correctly |
| 136 | * because the unlock should come after the last continue_to() (additionally, if |
| 137 | * you're using the closure asynchronously a mutex won't work since a mutex has |
| 138 | * to be unlocked by the same process that locked it). |
| 139 | * |
| 140 | * So to make it less error prone and more efficient, we also have the ability |
| 141 | * to use closures as locks: |
| 142 | * |
| 143 | * closure_init_unlocked(); |
| 144 | * closure_trylock(); |
| 145 | * |
| 146 | * That's all we need for trylock() - the last closure_put() implicitly unlocks |
| 147 | * it for you. But for closure_lock(), we also need a wait list: |
| 148 | * |
| 149 | * struct closure_with_waitlist frobnicator_cl; |
| 150 | * |
| 151 | * closure_init_unlocked(&frobnicator_cl); |
| 152 | * closure_lock(&frobnicator_cl); |
| 153 | * |
| 154 | * A closure_with_waitlist embeds a closure and a wait list - much like struct |
| 155 | * delayed_work embeds a work item and a timer_list. The important thing is, use |
| 156 | * it exactly like you would a regular closure and closure_put() will magically |
| 157 | * handle everything for you. |
| 158 | * |
| 159 | * We've got closures that embed timers, too. They're called, appropriately |
| 160 | * enough: |
| 161 | * struct closure_with_timer; |
| 162 | * |
| 163 | * This gives you access to closure_delay(). It takes a refcount for a specified |
| 164 | * number of jiffies - you could then call closure_sync() (for a slightly |
| 165 | * convoluted version of msleep()) or continue_at() - which gives you the same |
| 166 | * effect as using a delayed work item, except you can reuse the work_struct |
| 167 | * already embedded in struct closure. |
| 168 | * |
| 169 | * Lastly, there's struct closure_with_waitlist_and_timer. It does what you |
| 170 | * probably expect, if you happen to need the features of both. (You don't |
| 171 | * really want to know how all this is implemented, but if I've done my job |
| 172 | * right you shouldn't have to care). |
| 173 | */ |
| 174 | |
| 175 | struct closure; |
| 176 | typedef void (closure_fn) (struct closure *); |
| 177 | |
| 178 | struct closure_waitlist { |
| 179 | struct llist_head list; |
| 180 | }; |
| 181 | |
| 182 | enum closure_type { |
| 183 | TYPE_closure = 0, |
| 184 | TYPE_closure_with_waitlist = 1, |
| 185 | TYPE_closure_with_timer = 2, |
| 186 | TYPE_closure_with_waitlist_and_timer = 3, |
| 187 | MAX_CLOSURE_TYPE = 3, |
| 188 | }; |
| 189 | |
| 190 | enum closure_state { |
| 191 | /* |
| 192 | * CLOSURE_BLOCKING: Causes closure_wait_event() to block, instead of |
| 193 | * waiting asynchronously |
| 194 | * |
| 195 | * CLOSURE_WAITING: Set iff the closure is on a waitlist. Must be set by |
| 196 | * the thread that owns the closure, and cleared by the thread that's |
| 197 | * waking up the closure. |
| 198 | * |
| 199 | * CLOSURE_SLEEPING: Must be set before a thread uses a closure to sleep |
| 200 | * - indicates that cl->task is valid and closure_put() may wake it up. |
| 201 | * Only set or cleared by the thread that owns the closure. |
| 202 | * |
| 203 | * CLOSURE_TIMER: Analagous to CLOSURE_WAITING, indicates that a closure |
| 204 | * has an outstanding timer. Must be set by the thread that owns the |
| 205 | * closure, and cleared by the timer function when the timer goes off. |
| 206 | * |
| 207 | * The rest are for debugging and don't affect behaviour: |
| 208 | * |
| 209 | * CLOSURE_RUNNING: Set when a closure is running (i.e. by |
| 210 | * closure_init() and when closure_put() runs then next function), and |
| 211 | * must be cleared before remaining hits 0. Primarily to help guard |
| 212 | * against incorrect usage and accidentally transferring references. |
| 213 | * continue_at() and closure_return() clear it for you, if you're doing |
| 214 | * something unusual you can use closure_set_dead() which also helps |
| 215 | * annotate where references are being transferred. |
| 216 | * |
| 217 | * CLOSURE_STACK: Sanity check - remaining should never hit 0 on a |
| 218 | * closure with this flag set |
| 219 | */ |
| 220 | |
| 221 | CLOSURE_BITS_START = (1 << 19), |
| 222 | CLOSURE_DESTRUCTOR = (1 << 19), |
| 223 | CLOSURE_BLOCKING = (1 << 21), |
| 224 | CLOSURE_WAITING = (1 << 23), |
| 225 | CLOSURE_SLEEPING = (1 << 25), |
| 226 | CLOSURE_TIMER = (1 << 27), |
| 227 | CLOSURE_RUNNING = (1 << 29), |
| 228 | CLOSURE_STACK = (1 << 31), |
| 229 | }; |
| 230 | |
| 231 | #define CLOSURE_GUARD_MASK \ |
| 232 | ((CLOSURE_DESTRUCTOR|CLOSURE_BLOCKING|CLOSURE_WAITING| \ |
| 233 | CLOSURE_SLEEPING|CLOSURE_TIMER|CLOSURE_RUNNING|CLOSURE_STACK) << 1) |
| 234 | |
| 235 | #define CLOSURE_REMAINING_MASK (CLOSURE_BITS_START - 1) |
| 236 | #define CLOSURE_REMAINING_INITIALIZER (1|CLOSURE_RUNNING) |
| 237 | |
| 238 | struct closure { |
| 239 | union { |
| 240 | struct { |
| 241 | struct workqueue_struct *wq; |
| 242 | struct task_struct *task; |
| 243 | struct llist_node list; |
| 244 | closure_fn *fn; |
| 245 | }; |
| 246 | struct work_struct work; |
| 247 | }; |
| 248 | |
| 249 | struct closure *parent; |
| 250 | |
| 251 | atomic_t remaining; |
| 252 | |
| 253 | enum closure_type type; |
| 254 | |
| 255 | #ifdef CONFIG_BCACHE_CLOSURES_DEBUG |
| 256 | #define CLOSURE_MAGIC_DEAD 0xc054dead |
| 257 | #define CLOSURE_MAGIC_ALIVE 0xc054a11e |
| 258 | |
| 259 | unsigned magic; |
| 260 | struct list_head all; |
| 261 | unsigned long ip; |
| 262 | unsigned long waiting_on; |
| 263 | #endif |
| 264 | }; |
| 265 | |
| 266 | struct closure_with_waitlist { |
| 267 | struct closure cl; |
| 268 | struct closure_waitlist wait; |
| 269 | }; |
| 270 | |
| 271 | struct closure_with_timer { |
| 272 | struct closure cl; |
| 273 | struct timer_list timer; |
| 274 | }; |
| 275 | |
| 276 | struct closure_with_waitlist_and_timer { |
| 277 | struct closure cl; |
| 278 | struct closure_waitlist wait; |
| 279 | struct timer_list timer; |
| 280 | }; |
| 281 | |
| 282 | extern unsigned invalid_closure_type(void); |
| 283 | |
| 284 | #define __CLOSURE_TYPE(cl, _t) \ |
| 285 | __builtin_types_compatible_p(typeof(cl), struct _t) \ |
| 286 | ? TYPE_ ## _t : \ |
| 287 | |
| 288 | #define __closure_type(cl) \ |
| 289 | ( \ |
| 290 | __CLOSURE_TYPE(cl, closure) \ |
| 291 | __CLOSURE_TYPE(cl, closure_with_waitlist) \ |
| 292 | __CLOSURE_TYPE(cl, closure_with_timer) \ |
| 293 | __CLOSURE_TYPE(cl, closure_with_waitlist_and_timer) \ |
| 294 | invalid_closure_type() \ |
| 295 | ) |
| 296 | |
| 297 | void closure_sub(struct closure *cl, int v); |
| 298 | void closure_put(struct closure *cl); |
| 299 | void closure_queue(struct closure *cl); |
| 300 | void __closure_wake_up(struct closure_waitlist *list); |
| 301 | bool closure_wait(struct closure_waitlist *list, struct closure *cl); |
| 302 | void closure_sync(struct closure *cl); |
| 303 | |
| 304 | bool closure_trylock(struct closure *cl, struct closure *parent); |
| 305 | void __closure_lock(struct closure *cl, struct closure *parent, |
| 306 | struct closure_waitlist *wait_list); |
| 307 | |
| 308 | void do_closure_timer_init(struct closure *cl); |
| 309 | bool __closure_delay(struct closure *cl, unsigned long delay, |
| 310 | struct timer_list *timer); |
| 311 | void __closure_flush(struct closure *cl, struct timer_list *timer); |
| 312 | void __closure_flush_sync(struct closure *cl, struct timer_list *timer); |
| 313 | |
| 314 | #ifdef CONFIG_BCACHE_CLOSURES_DEBUG |
| 315 | |
Kent Overstreet | 07e86cc | 2013-03-25 11:46:43 -0700 | [diff] [blame^] | 316 | void closure_debug_init(void); |
Kent Overstreet | cafe563 | 2013-03-23 16:11:31 -0700 | [diff] [blame] | 317 | void closure_debug_create(struct closure *cl); |
| 318 | void closure_debug_destroy(struct closure *cl); |
| 319 | |
| 320 | #else |
| 321 | |
Kent Overstreet | 07e86cc | 2013-03-25 11:46:43 -0700 | [diff] [blame^] | 322 | static inline void closure_debug_init(void) {} |
Kent Overstreet | cafe563 | 2013-03-23 16:11:31 -0700 | [diff] [blame] | 323 | static inline void closure_debug_create(struct closure *cl) {} |
| 324 | static inline void closure_debug_destroy(struct closure *cl) {} |
| 325 | |
| 326 | #endif |
| 327 | |
| 328 | static inline void closure_set_ip(struct closure *cl) |
| 329 | { |
| 330 | #ifdef CONFIG_BCACHE_CLOSURES_DEBUG |
| 331 | cl->ip = _THIS_IP_; |
| 332 | #endif |
| 333 | } |
| 334 | |
| 335 | static inline void closure_set_ret_ip(struct closure *cl) |
| 336 | { |
| 337 | #ifdef CONFIG_BCACHE_CLOSURES_DEBUG |
| 338 | cl->ip = _RET_IP_; |
| 339 | #endif |
| 340 | } |
| 341 | |
| 342 | static inline void closure_get(struct closure *cl) |
| 343 | { |
| 344 | #ifdef CONFIG_BCACHE_CLOSURES_DEBUG |
| 345 | BUG_ON((atomic_inc_return(&cl->remaining) & |
| 346 | CLOSURE_REMAINING_MASK) <= 1); |
| 347 | #else |
| 348 | atomic_inc(&cl->remaining); |
| 349 | #endif |
| 350 | } |
| 351 | |
| 352 | static inline void closure_set_stopped(struct closure *cl) |
| 353 | { |
| 354 | atomic_sub(CLOSURE_RUNNING, &cl->remaining); |
| 355 | } |
| 356 | |
| 357 | static inline bool closure_is_stopped(struct closure *cl) |
| 358 | { |
| 359 | return !(atomic_read(&cl->remaining) & CLOSURE_RUNNING); |
| 360 | } |
| 361 | |
| 362 | static inline bool closure_is_unlocked(struct closure *cl) |
| 363 | { |
| 364 | return atomic_read(&cl->remaining) == -1; |
| 365 | } |
| 366 | |
| 367 | static inline void do_closure_init(struct closure *cl, struct closure *parent, |
| 368 | bool running) |
| 369 | { |
| 370 | switch (cl->type) { |
| 371 | case TYPE_closure_with_timer: |
| 372 | case TYPE_closure_with_waitlist_and_timer: |
| 373 | do_closure_timer_init(cl); |
| 374 | default: |
| 375 | break; |
| 376 | } |
| 377 | |
| 378 | cl->parent = parent; |
| 379 | if (parent) |
| 380 | closure_get(parent); |
| 381 | |
| 382 | if (running) { |
| 383 | closure_debug_create(cl); |
| 384 | atomic_set(&cl->remaining, CLOSURE_REMAINING_INITIALIZER); |
| 385 | } else |
| 386 | atomic_set(&cl->remaining, -1); |
| 387 | |
| 388 | closure_set_ip(cl); |
| 389 | } |
| 390 | |
| 391 | /* |
| 392 | * Hack to get at the embedded closure if there is one, by doing an unsafe cast: |
| 393 | * the result of __closure_type() is thrown away, it's used merely for type |
| 394 | * checking. |
| 395 | */ |
| 396 | #define __to_internal_closure(cl) \ |
| 397 | ({ \ |
| 398 | BUILD_BUG_ON(__closure_type(*cl) > MAX_CLOSURE_TYPE); \ |
| 399 | (struct closure *) cl; \ |
| 400 | }) |
| 401 | |
| 402 | #define closure_init_type(cl, parent, running) \ |
| 403 | do { \ |
| 404 | struct closure *_cl = __to_internal_closure(cl); \ |
| 405 | _cl->type = __closure_type(*(cl)); \ |
| 406 | do_closure_init(_cl, parent, running); \ |
| 407 | } while (0) |
| 408 | |
| 409 | /** |
| 410 | * __closure_init() - Initialize a closure, skipping the memset() |
| 411 | * |
| 412 | * May be used instead of closure_init() when memory has already been zeroed. |
| 413 | */ |
| 414 | #define __closure_init(cl, parent) \ |
| 415 | closure_init_type(cl, parent, true) |
| 416 | |
| 417 | /** |
| 418 | * closure_init() - Initialize a closure, setting the refcount to 1 |
| 419 | * @cl: closure to initialize |
| 420 | * @parent: parent of the new closure. cl will take a refcount on it for its |
| 421 | * lifetime; may be NULL. |
| 422 | */ |
| 423 | #define closure_init(cl, parent) \ |
| 424 | do { \ |
| 425 | memset((cl), 0, sizeof(*(cl))); \ |
| 426 | __closure_init(cl, parent); \ |
| 427 | } while (0) |
| 428 | |
| 429 | static inline void closure_init_stack(struct closure *cl) |
| 430 | { |
| 431 | memset(cl, 0, sizeof(struct closure)); |
| 432 | atomic_set(&cl->remaining, CLOSURE_REMAINING_INITIALIZER| |
| 433 | CLOSURE_BLOCKING|CLOSURE_STACK); |
| 434 | } |
| 435 | |
| 436 | /** |
| 437 | * closure_init_unlocked() - Initialize a closure but leave it unlocked. |
| 438 | * @cl: closure to initialize |
| 439 | * |
| 440 | * For when the closure will be used as a lock. The closure may not be used |
| 441 | * until after a closure_lock() or closure_trylock(). |
| 442 | */ |
| 443 | #define closure_init_unlocked(cl) \ |
| 444 | do { \ |
| 445 | memset((cl), 0, sizeof(*(cl))); \ |
| 446 | closure_init_type(cl, NULL, false); \ |
| 447 | } while (0) |
| 448 | |
| 449 | /** |
| 450 | * closure_lock() - lock and initialize a closure. |
| 451 | * @cl: the closure to lock |
| 452 | * @parent: the new parent for this closure |
| 453 | * |
| 454 | * The closure must be of one of the types that has a waitlist (otherwise we |
| 455 | * wouldn't be able to sleep on contention). |
| 456 | * |
| 457 | * @parent has exactly the same meaning as in closure_init(); if non null, the |
| 458 | * closure will take a reference on @parent which will be released when it is |
| 459 | * unlocked. |
| 460 | */ |
| 461 | #define closure_lock(cl, parent) \ |
| 462 | __closure_lock(__to_internal_closure(cl), parent, &(cl)->wait) |
| 463 | |
| 464 | /** |
| 465 | * closure_delay() - delay some number of jiffies |
| 466 | * @cl: the closure that will sleep |
| 467 | * @delay: the delay in jiffies |
| 468 | * |
| 469 | * Takes a refcount on @cl which will be released after @delay jiffies; this may |
| 470 | * be used to have a function run after a delay with continue_at(), or |
| 471 | * closure_sync() may be used for a convoluted version of msleep(). |
| 472 | */ |
| 473 | #define closure_delay(cl, delay) \ |
| 474 | __closure_delay(__to_internal_closure(cl), delay, &(cl)->timer) |
| 475 | |
| 476 | #define closure_flush(cl) \ |
| 477 | __closure_flush(__to_internal_closure(cl), &(cl)->timer) |
| 478 | |
| 479 | #define closure_flush_sync(cl) \ |
| 480 | __closure_flush_sync(__to_internal_closure(cl), &(cl)->timer) |
| 481 | |
| 482 | static inline void __closure_end_sleep(struct closure *cl) |
| 483 | { |
| 484 | __set_current_state(TASK_RUNNING); |
| 485 | |
| 486 | if (atomic_read(&cl->remaining) & CLOSURE_SLEEPING) |
| 487 | atomic_sub(CLOSURE_SLEEPING, &cl->remaining); |
| 488 | } |
| 489 | |
| 490 | static inline void __closure_start_sleep(struct closure *cl) |
| 491 | { |
| 492 | closure_set_ip(cl); |
| 493 | cl->task = current; |
| 494 | set_current_state(TASK_UNINTERRUPTIBLE); |
| 495 | |
| 496 | if (!(atomic_read(&cl->remaining) & CLOSURE_SLEEPING)) |
| 497 | atomic_add(CLOSURE_SLEEPING, &cl->remaining); |
| 498 | } |
| 499 | |
| 500 | /** |
| 501 | * closure_blocking() - returns true if the closure is in blocking mode. |
| 502 | * |
| 503 | * If a closure is in blocking mode, closure_wait_event() will sleep until the |
| 504 | * condition is true instead of waiting asynchronously. |
| 505 | */ |
| 506 | static inline bool closure_blocking(struct closure *cl) |
| 507 | { |
| 508 | return atomic_read(&cl->remaining) & CLOSURE_BLOCKING; |
| 509 | } |
| 510 | |
| 511 | /** |
| 512 | * set_closure_blocking() - put a closure in blocking mode. |
| 513 | * |
| 514 | * If a closure is in blocking mode, closure_wait_event() will sleep until the |
| 515 | * condition is true instead of waiting asynchronously. |
| 516 | * |
| 517 | * Not thread safe - can only be called by the thread running the closure. |
| 518 | */ |
| 519 | static inline void set_closure_blocking(struct closure *cl) |
| 520 | { |
| 521 | if (!closure_blocking(cl)) |
| 522 | atomic_add(CLOSURE_BLOCKING, &cl->remaining); |
| 523 | } |
| 524 | |
| 525 | /* |
| 526 | * Not thread safe - can only be called by the thread running the closure. |
| 527 | */ |
| 528 | static inline void clear_closure_blocking(struct closure *cl) |
| 529 | { |
| 530 | if (closure_blocking(cl)) |
| 531 | atomic_sub(CLOSURE_BLOCKING, &cl->remaining); |
| 532 | } |
| 533 | |
| 534 | /** |
| 535 | * closure_wake_up() - wake up all closures on a wait list. |
| 536 | */ |
| 537 | static inline void closure_wake_up(struct closure_waitlist *list) |
| 538 | { |
| 539 | smp_mb(); |
| 540 | __closure_wake_up(list); |
| 541 | } |
| 542 | |
| 543 | /* |
| 544 | * Wait on an event, synchronously or asynchronously - analogous to wait_event() |
| 545 | * but for closures. |
| 546 | * |
| 547 | * The loop is oddly structured so as to avoid a race; we must check the |
| 548 | * condition again after we've added ourself to the waitlist. We know if we were |
| 549 | * already on the waitlist because closure_wait() returns false; thus, we only |
| 550 | * schedule or break if closure_wait() returns false. If it returns true, we |
| 551 | * just loop again - rechecking the condition. |
| 552 | * |
| 553 | * The __closure_wake_up() is necessary because we may race with the event |
| 554 | * becoming true; i.e. we see event false -> wait -> recheck condition, but the |
| 555 | * thread that made the event true may have called closure_wake_up() before we |
| 556 | * added ourself to the wait list. |
| 557 | * |
| 558 | * We have to call closure_sync() at the end instead of just |
| 559 | * __closure_end_sleep() because a different thread might've called |
| 560 | * closure_wake_up() before us and gotten preempted before they dropped the |
| 561 | * refcount on our closure. If this was a stack allocated closure, that would be |
| 562 | * bad. |
| 563 | */ |
| 564 | #define __closure_wait_event(list, cl, condition, _block) \ |
| 565 | ({ \ |
| 566 | bool block = _block; \ |
| 567 | typeof(condition) ret; \ |
| 568 | \ |
| 569 | while (1) { \ |
| 570 | ret = (condition); \ |
| 571 | if (ret) { \ |
| 572 | __closure_wake_up(list); \ |
| 573 | if (block) \ |
| 574 | closure_sync(cl); \ |
| 575 | \ |
| 576 | break; \ |
| 577 | } \ |
| 578 | \ |
| 579 | if (block) \ |
| 580 | __closure_start_sleep(cl); \ |
| 581 | \ |
| 582 | if (!closure_wait(list, cl)) { \ |
| 583 | if (!block) \ |
| 584 | break; \ |
| 585 | \ |
| 586 | schedule(); \ |
| 587 | } \ |
| 588 | } \ |
| 589 | \ |
| 590 | ret; \ |
| 591 | }) |
| 592 | |
| 593 | /** |
| 594 | * closure_wait_event() - wait on a condition, synchronously or asynchronously. |
| 595 | * @list: the wait list to wait on |
| 596 | * @cl: the closure that is doing the waiting |
| 597 | * @condition: a C expression for the event to wait for |
| 598 | * |
| 599 | * If the closure is in blocking mode, sleeps until the @condition evaluates to |
| 600 | * true - exactly like wait_event(). |
| 601 | * |
| 602 | * If the closure is not in blocking mode, waits asynchronously; if the |
| 603 | * condition is currently false the @cl is put onto @list and returns. @list |
| 604 | * owns a refcount on @cl; closure_sync() or continue_at() may be used later to |
| 605 | * wait for another thread to wake up @list, which drops the refcount on @cl. |
| 606 | * |
| 607 | * Returns the value of @condition; @cl will be on @list iff @condition was |
| 608 | * false. |
| 609 | * |
| 610 | * closure_wake_up(@list) must be called after changing any variable that could |
| 611 | * cause @condition to become true. |
| 612 | */ |
| 613 | #define closure_wait_event(list, cl, condition) \ |
| 614 | __closure_wait_event(list, cl, condition, closure_blocking(cl)) |
| 615 | |
| 616 | #define closure_wait_event_async(list, cl, condition) \ |
| 617 | __closure_wait_event(list, cl, condition, false) |
| 618 | |
| 619 | #define closure_wait_event_sync(list, cl, condition) \ |
| 620 | __closure_wait_event(list, cl, condition, true) |
| 621 | |
| 622 | static inline void set_closure_fn(struct closure *cl, closure_fn *fn, |
| 623 | struct workqueue_struct *wq) |
| 624 | { |
| 625 | BUG_ON(object_is_on_stack(cl)); |
| 626 | closure_set_ip(cl); |
| 627 | cl->fn = fn; |
| 628 | cl->wq = wq; |
| 629 | /* between atomic_dec() in closure_put() */ |
| 630 | smp_mb__before_atomic_dec(); |
| 631 | } |
| 632 | |
| 633 | #define continue_at(_cl, _fn, _wq) \ |
| 634 | do { \ |
| 635 | set_closure_fn(_cl, _fn, _wq); \ |
| 636 | closure_sub(_cl, CLOSURE_RUNNING + 1); \ |
| 637 | return; \ |
| 638 | } while (0) |
| 639 | |
| 640 | #define closure_return(_cl) continue_at((_cl), NULL, NULL) |
| 641 | |
| 642 | #define continue_at_nobarrier(_cl, _fn, _wq) \ |
| 643 | do { \ |
| 644 | set_closure_fn(_cl, _fn, _wq); \ |
| 645 | closure_queue(cl); \ |
| 646 | return; \ |
| 647 | } while (0) |
| 648 | |
| 649 | #define closure_return_with_destructor(_cl, _destructor) \ |
| 650 | do { \ |
| 651 | set_closure_fn(_cl, _destructor, NULL); \ |
| 652 | closure_sub(_cl, CLOSURE_RUNNING - CLOSURE_DESTRUCTOR + 1); \ |
| 653 | return; \ |
| 654 | } while (0) |
| 655 | |
| 656 | static inline void closure_call(struct closure *cl, closure_fn fn, |
| 657 | struct workqueue_struct *wq, |
| 658 | struct closure *parent) |
| 659 | { |
| 660 | closure_init(cl, parent); |
| 661 | continue_at_nobarrier(cl, fn, wq); |
| 662 | } |
| 663 | |
| 664 | static inline void closure_trylock_call(struct closure *cl, closure_fn fn, |
| 665 | struct workqueue_struct *wq, |
| 666 | struct closure *parent) |
| 667 | { |
| 668 | if (closure_trylock(cl, parent)) |
| 669 | continue_at_nobarrier(cl, fn, wq); |
| 670 | } |
| 671 | |
| 672 | #endif /* _LINUX_CLOSURE_H */ |