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_init(void);
 317 void closure_debug_create(struct closure *cl);
 318 void closure_debug_destroy(struct closure *cl);
 319
 320 #else
 321
 322 static inline void closure_debug_init(void) {}
 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 */