drivers/md/bcache/closure.h

   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
 316 void closure_debug_create(struct closure *cl);
 317 void closure_debug_destroy(struct closure *cl);
 318
 319 #else
 320
 321 static inline void closure_debug_create(struct closure *cl) {}
 322 static inline void closure_debug_destroy(struct closure *cl) {}
 323
 324 #endif
 325
 326 static inline void closure_set_ip(struct closure *cl)
 327 {
 328 #ifdef CONFIG_BCACHE_CLOSURES_DEBUG
 329         cl->ip = _THIS_IP_;
 330 #endif
 331 }
 332
 333 static inline void closure_set_ret_ip(struct closure *cl)
 334 {
 335 #ifdef CONFIG_BCACHE_CLOSURES_DEBUG
 336         cl->ip = _RET_IP_;
 337 #endif
 338 }
 339
 340 static inline void closure_get(struct closure *cl)
 341 {
 342 #ifdef CONFIG_BCACHE_CLOSURES_DEBUG
 343         BUG_ON((atomic_inc_return(&cl->remaining) &
 344                 CLOSURE_REMAINING_MASK) <= 1);
 345 #else
 346         atomic_inc(&cl->remaining);
 347 #endif
 348 }
 349
 350 static inline void closure_set_stopped(struct closure *cl)
 351 {
 352         atomic_sub(CLOSURE_RUNNING, &cl->remaining);
 353 }
 354
 355 static inline bool closure_is_stopped(struct closure *cl)
 356 {
 357         return !(atomic_read(&cl->remaining) & CLOSURE_RUNNING);
 358 }
 359
 360 static inline bool closure_is_unlocked(struct closure *cl)
 361 {
 362         return atomic_read(&cl->remaining) == -1;
 363 }
 364
 365 static inline void do_closure_init(struct closure *cl, struct closure *parent,
 366                                    bool running)
 367 {
 368         switch (cl->type) {
 369         case TYPE_closure_with_timer:
 370         case TYPE_closure_with_waitlist_and_timer:
 371                 do_closure_timer_init(cl);
 372         default:
 373                 break;
 374         }
 375
 376         cl->parent = parent;
 377         if (parent)
 378                 closure_get(parent);
 379
 380         if (running) {
 381                 closure_debug_create(cl);
 382                 atomic_set(&cl->remaining, CLOSURE_REMAINING_INITIALIZER);
 383         } else
 384                 atomic_set(&cl->remaining, -1);
 385
 386         closure_set_ip(cl);
 387 }
 388
 389 /*
 390  * Hack to get at the embedded closure if there is one, by doing an unsafe cast:
 391  * the result of __closure_type() is thrown away, it's used merely for type
 392  * checking.
 393  */
 394 #define __to_internal_closure(cl)                               \
 395 ({                                                              \
 396         BUILD_BUG_ON(__closure_type(*cl) > MAX_CLOSURE_TYPE);   \
 397         (struct closure *) cl;                                  \
 398 })
 399
 400 #define closure_init_type(cl, parent, running)                  \
 401 do {                                                            \
 402         struct closure *_cl = __to_internal_closure(cl);        \
 403         _cl->type = __closure_type(*(cl));                      \
 404         do_closure_init(_cl, parent, running);                  \
 405 } while (0)
 406
 407 /**
 408  * __closure_init() - Initialize a closure, skipping the memset()
 409  *
 410  * May be used instead of closure_init() when memory has already been zeroed.
 411  */
 412 #define __closure_init(cl, parent)                              \
 413         closure_init_type(cl, parent, true)
 414
 415 /**
 416  * closure_init() - Initialize a closure, setting the refcount to 1
 417  * @cl:         closure to initialize
 418  * @parent:     parent of the new closure. cl will take a refcount on it for its
 419  *              lifetime; may be NULL.
 420  */
 421 #define closure_init(cl, parent)                                \
 422 do {                                                            \
 423         memset((cl), 0, sizeof(*(cl)));                         \
 424         __closure_init(cl, parent);                             \
 425 } while (0)
 426
 427 static inline void closure_init_stack(struct closure *cl)
 428 {
 429         memset(cl, 0, sizeof(struct closure));
 430         atomic_set(&cl->remaining, CLOSURE_REMAINING_INITIALIZER|
 431                    CLOSURE_BLOCKING|CLOSURE_STACK);
 432 }
 433
 434 /**
 435  * closure_init_unlocked() - Initialize a closure but leave it unlocked.
 436  * @cl:         closure to initialize
 437  *
 438  * For when the closure will be used as a lock. The closure may not be used
 439  * until after a closure_lock() or closure_trylock().
 440  */
 441 #define closure_init_unlocked(cl)                               \
 442 do {                                                            \
 443         memset((cl), 0, sizeof(*(cl)));                         \
 444         closure_init_type(cl, NULL, false);                     \
 445 } while (0)
 446
 447 /**
 448  * closure_lock() - lock and initialize a closure.
 449  * @cl:         the closure to lock
 450  * @parent:     the new parent for this closure
 451  *
 452  * The closure must be of one of the types that has a waitlist (otherwise we
 453  * wouldn't be able to sleep on contention).
 454  *
 455  * @parent has exactly the same meaning as in closure_init(); if non null, the
 456  * closure will take a reference on @parent which will be released when it is
 457  * unlocked.
 458  */
 459 #define closure_lock(cl, parent)                                \
 460         __closure_lock(__to_internal_closure(cl), parent, &(cl)->wait)
 461
 462 /**
 463  * closure_delay() - delay some number of jiffies
 464  * @cl:         the closure that will sleep
 465  * @delay:      the delay in jiffies
 466  *
 467  * Takes a refcount on @cl which will be released after @delay jiffies; this may
 468  * be used to have a function run after a delay with continue_at(), or
 469  * closure_sync() may be used for a convoluted version of msleep().
 470  */
 471 #define closure_delay(cl, delay)                        \
 472         __closure_delay(__to_internal_closure(cl), delay, &(cl)->timer)
 473
 474 #define closure_flush(cl)                               \
 475         __closure_flush(__to_internal_closure(cl), &(cl)->timer)
 476
 477 #define closure_flush_sync(cl)                          \
 478         __closure_flush_sync(__to_internal_closure(cl), &(cl)->timer)
 479
 480 static inline void __closure_end_sleep(struct closure *cl)
 481 {
 482         __set_current_state(TASK_RUNNING);
 483
 484         if (atomic_read(&cl->remaining) & CLOSURE_SLEEPING)
 485                 atomic_sub(CLOSURE_SLEEPING, &cl->remaining);
 486 }
 487
 488 static inline void __closure_start_sleep(struct closure *cl)
 489 {
 490         closure_set_ip(cl);
 491         cl->task = current;
 492         set_current_state(TASK_UNINTERRUPTIBLE);
 493
 494         if (!(atomic_read(&cl->remaining) & CLOSURE_SLEEPING))
 495                 atomic_add(CLOSURE_SLEEPING, &cl->remaining);
 496 }
 497
 498 /**
 499  * closure_blocking() - returns true if the closure is in blocking mode.
 500  *
 501  * If a closure is in blocking mode, closure_wait_event() will sleep until the
 502  * condition is true instead of waiting asynchronously.
 503  */
 504 static inline bool closure_blocking(struct closure *cl)
 505 {
 506         return atomic_read(&cl->remaining) & CLOSURE_BLOCKING;
 507 }
 508
 509 /**
 510  * set_closure_blocking() - put a closure in blocking mode.
 511  *
 512  * If a closure is in blocking mode, closure_wait_event() will sleep until the
 513  * condition is true instead of waiting asynchronously.
 514  *
 515  * Not thread safe - can only be called by the thread running the closure.
 516  */
 517 static inline void set_closure_blocking(struct closure *cl)
 518 {
 519         if (!closure_blocking(cl))
 520                 atomic_add(CLOSURE_BLOCKING, &cl->remaining);
 521 }
 522
 523 /*
 524  * Not thread safe - can only be called by the thread running the closure.
 525  */
 526 static inline void clear_closure_blocking(struct closure *cl)
 527 {
 528         if (closure_blocking(cl))
 529                 atomic_sub(CLOSURE_BLOCKING, &cl->remaining);
 530 }
 531
 532 /**
 533  * closure_wake_up() - wake up all closures on a wait list.
 534  */
 535 static inline void closure_wake_up(struct closure_waitlist *list)
 536 {
 537         smp_mb();
 538         __closure_wake_up(list);
 539 }
 540
 541 /*
 542  * Wait on an event, synchronously or asynchronously - analogous to wait_event()
 543  * but for closures.
 544  *
 545  * The loop is oddly structured so as to avoid a race; we must check the
 546  * condition again after we've added ourself to the waitlist. We know if we were
 547  * already on the waitlist because closure_wait() returns false; thus, we only
 548  * schedule or break if closure_wait() returns false. If it returns true, we
 549  * just loop again - rechecking the condition.
 550  *
 551  * The __closure_wake_up() is necessary because we may race with the event
 552  * becoming true; i.e. we see event false -> wait -> recheck condition, but the
 553  * thread that made the event true may have called closure_wake_up() before we
 554  * added ourself to the wait list.
 555  *
 556  * We have to call closure_sync() at the end instead of just
 557  * __closure_end_sleep() because a different thread might've called
 558  * closure_wake_up() before us and gotten preempted before they dropped the
 559  * refcount on our closure. If this was a stack allocated closure, that would be
 560  * bad.
 561  */
 562 #define __closure_wait_event(list, cl, condition, _block)               \
 563 ({                                                                      \
 564         bool block = _block;                                            \
 565         typeof(condition) ret;                                          \
 566                                                                         \
 567         while (1) {                                                     \
 568                 ret = (condition);                                      \
 569                 if (ret) {                                              \
 570                         __closure_wake_up(list);                        \
 571                         if (block)                                      \
 572                                 closure_sync(cl);                       \
 573                                                                         \
 574                         break;                                          \
 575                 }                                                       \
 576                                                                         \
 577                 if (block)                                              \
 578                         __closure_start_sleep(cl);                      \
 579                                                                         \
 580                 if (!closure_wait(list, cl)) {                          \
 581                         if (!block)                                     \
 582                                 break;                                  \
 583                                                                         \
 584                         schedule();                                     \
 585                 }                                                       \
 586         }                                                               \
 587                                                                         \
 588         ret;                                                            \
 589 })
 590
 591 /**
 592  * closure_wait_event() - wait on a condition, synchronously or asynchronously.
 593  * @list:       the wait list to wait on
 594  * @cl:         the closure that is doing the waiting
 595  * @condition:  a C expression for the event to wait for
 596  *
 597  * If the closure is in blocking mode, sleeps until the @condition evaluates to
 598  * true - exactly like wait_event().
 599  *
 600  * If the closure is not in blocking mode, waits asynchronously; if the
 601  * condition is currently false the @cl is put onto @list and returns. @list
 602  * owns a refcount on @cl; closure_sync() or continue_at() may be used later to
 603  * wait for another thread to wake up @list, which drops the refcount on @cl.
 604  *
 605  * Returns the value of @condition; @cl will be on @list iff @condition was
 606  * false.
 607  *
 608  * closure_wake_up(@list) must be called after changing any variable that could
 609  * cause @condition to become true.
 610  */
 611 #define closure_wait_event(list, cl, condition)                         \
 612         __closure_wait_event(list, cl, condition, closure_blocking(cl))
 613
 614 #define closure_wait_event_async(list, cl, condition)                   \
 615         __closure_wait_event(list, cl, condition, false)
 616
 617 #define closure_wait_event_sync(list, cl, condition)                    \
 618         __closure_wait_event(list, cl, condition, true)
 619
 620 static inline void set_closure_fn(struct closure *cl, closure_fn *fn,
 621                                   struct workqueue_struct *wq)
 622 {
 623         BUG_ON(object_is_on_stack(cl));
 624         closure_set_ip(cl);
 625         cl->fn = fn;
 626         cl->wq = wq;
 627         /* between atomic_dec() in closure_put() */
 628         smp_mb__before_atomic_dec();
 629 }
 630
 631 #define continue_at(_cl, _fn, _wq)                                      \
 632 do {                                                                    \
 633         set_closure_fn(_cl, _fn, _wq);                                  \
 634         closure_sub(_cl, CLOSURE_RUNNING + 1);                          \
 635         return;                                                         \
 636 } while (0)
 637
 638 #define closure_return(_cl)     continue_at((_cl), NULL, NULL)
 639
 640 #define continue_at_nobarrier(_cl, _fn, _wq)                            \
 641 do {                                                                    \
 642         set_closure_fn(_cl, _fn, _wq);                                  \
 643         closure_queue(cl);                                              \
 644         return;                                                         \
 645 } while (0)
 646
 647 #define closure_return_with_destructor(_cl, _destructor)                \
 648 do {                                                                    \
 649         set_closure_fn(_cl, _destructor, NULL);                         \
 650         closure_sub(_cl, CLOSURE_RUNNING - CLOSURE_DESTRUCTOR + 1);     \
 651         return;                                                         \
 652 } while (0)
 653
 654 static inline void closure_call(struct closure *cl, closure_fn fn,
 655                                 struct workqueue_struct *wq,
 656                                 struct closure *parent)
 657 {
 658         closure_init(cl, parent);
 659         continue_at_nobarrier(cl, fn, wq);
 660 }
 661
 662 static inline void closure_trylock_call(struct closure *cl, closure_fn fn,
 663                                         struct workqueue_struct *wq,
 664                                         struct closure *parent)
 665 {
 666         if (closure_trylock(cl, parent))
 667                 continue_at_nobarrier(cl, fn, wq);
 668 }
 669
 670 #endif /* _LINUX_CLOSURE_H */