include/block/aio.h

   1 /*
   2  * QEMU aio implementation
   3  *
   4  * Copyright IBM, Corp. 2008
   5  *
   6  * Authors:
   7  *  Anthony Liguori   <aliguori@us.ibm.com>
   8  *
   9  * This work is licensed under the terms of the GNU GPL, version 2.  See
  10  * the COPYING file in the top-level directory.
  11  *
  12  */
  13
  14 #ifndef QEMU_AIO_H
  15 #define QEMU_AIO_H
  16
  17 #ifdef CONFIG_LINUX_IO_URING
  18 #include <liburing.h>
  19 #endif
  20 #include "qemu/coroutine.h"
  21 #include "qemu/queue.h"
  22 #include "qemu/event_notifier.h"
  23 #include "qemu/thread.h"
  24 #include "qemu/timer.h"
  25
  26 typedef struct BlockAIOCB BlockAIOCB;
  27 typedef void BlockCompletionFunc(void *opaque, int ret);
  28
  29 typedef struct AIOCBInfo {
  30     void (*cancel_async)(BlockAIOCB *acb);
  31     AioContext *(*get_aio_context)(BlockAIOCB *acb);
  32     size_t aiocb_size;
  33 } AIOCBInfo;
  34
  35 struct BlockAIOCB {
  36     const AIOCBInfo *aiocb_info;
  37     BlockDriverState *bs;
  38     BlockCompletionFunc *cb;
  39     void *opaque;
  40     int refcnt;
  41 };
  42
  43 void *qemu_aio_get(const AIOCBInfo *aiocb_info, BlockDriverState *bs,
  44                    BlockCompletionFunc *cb, void *opaque);
  45 void qemu_aio_unref(void *p);
  46 void qemu_aio_ref(void *p);
  47
  48 typedef struct AioHandler AioHandler;
  49 typedef QLIST_HEAD(, AioHandler) AioHandlerList;
  50 typedef void QEMUBHFunc(void *opaque);
  51 typedef bool AioPollFn(void *opaque);
  52 typedef void IOHandler(void *opaque);
  53
  54 struct Coroutine;
  55 struct ThreadPool;
  56 struct LinuxAioState;
  57 struct LuringState;
  58
  59 /* Is polling disabled? */
  60 bool aio_poll_disabled(AioContext *ctx);
  61
  62 /* Callbacks for file descriptor monitoring implementations */
  63 typedef struct {
  64     /*
  65      * update:
  66      * @ctx: the AioContext
  67      * @old_node: the existing handler or NULL if this file descriptor is being
  68      *            monitored for the first time
  69      * @new_node: the new handler or NULL if this file descriptor is being
  70      *            removed
  71      *
  72      * Add/remove/modify a monitored file descriptor.
  73      *
  74      * Called with ctx->list_lock acquired.
  75      */
  76     void (*update)(AioContext *ctx, AioHandler *old_node, AioHandler *new_node);
  77
  78     /*
  79      * wait:
  80      * @ctx: the AioContext
  81      * @ready_list: list for handlers that become ready
  82      * @timeout: maximum duration to wait, in nanoseconds
  83      *
  84      * Wait for file descriptors to become ready and place them on ready_list.
  85      *
  86      * Called with ctx->list_lock incremented but not locked.
  87      *
  88      * Returns: number of ready file descriptors.
  89      */
  90     int (*wait)(AioContext *ctx, AioHandlerList *ready_list, int64_t timeout);
  91
  92     /*
  93      * need_wait:
  94      * @ctx: the AioContext
  95      *
  96      * Tell aio_poll() when to stop userspace polling early because ->wait()
  97      * has fds ready.
  98      *
  99      * File descriptor monitoring implementations that cannot poll fd readiness
 100      * from userspace should use aio_poll_disabled() here.  This ensures that
 101      * file descriptors are not starved by handlers that frequently make
 102      * progress via userspace polling.
 103      *
 104      * Returns: true if ->wait() should be called, false otherwise.
 105      */
 106     bool (*need_wait)(AioContext *ctx);
 107 } FDMonOps;
 108
 109 /*
 110  * Each aio_bh_poll() call carves off a slice of the BH list, so that newly
 111  * scheduled BHs are not processed until the next aio_bh_poll() call.  All
 112  * active aio_bh_poll() calls chain their slices together in a list, so that
 113  * nested aio_bh_poll() calls process all scheduled bottom halves.
 114  */
 115 typedef QSLIST_HEAD(, QEMUBH) BHList;
 116 typedef struct BHListSlice BHListSlice;
 117 struct BHListSlice {
 118     BHList bh_list;
 119     QSIMPLEQ_ENTRY(BHListSlice) next;
 120 };
 121
 122 typedef QSLIST_HEAD(, AioHandler) AioHandlerSList;
 123
 124 struct AioContext {
 125     GSource source;
 126
 127     /* Used by AioContext users to protect from multi-threaded access.  */
 128     QemuRecMutex lock;
 129
 130     /* The list of registered AIO handlers.  Protected by ctx->list_lock. */
 131     AioHandlerList aio_handlers;
 132
 133     /* The list of AIO handlers to be deleted.  Protected by ctx->list_lock. */
 134     AioHandlerList deleted_aio_handlers;
 135
 136     /* Used to avoid unnecessary event_notifier_set calls in aio_notify;
 137      * only written from the AioContext home thread, or under the BQL in
 138      * the case of the main AioContext.  However, it is read from any
 139      * thread so it is still accessed with atomic primitives.
 140      *
 141      * If this field is 0, everything (file descriptors, bottom halves,
 142      * timers) will be re-evaluated before the next blocking poll() or
 143      * io_uring wait; therefore, the event_notifier_set call can be
 144      * skipped.  If it is non-zero, you may need to wake up a concurrent
 145      * aio_poll or the glib main event loop, making event_notifier_set
 146      * necessary.
 147      *
 148      * Bit 0 is reserved for GSource usage of the AioContext, and is 1
 149      * between a call to aio_ctx_prepare and the next call to aio_ctx_check.
 150      * Bits 1-31 simply count the number of active calls to aio_poll
 151      * that are in the prepare or poll phase.
 152      *
 153      * The GSource and aio_poll must use a different mechanism because
 154      * there is no certainty that a call to GSource's prepare callback
 155      * (via g_main_context_prepare) is indeed followed by check and
 156      * dispatch.  It's not clear whether this would be a bug, but let's
 157      * play safe and allow it---it will just cause extra calls to
 158      * event_notifier_set until the next call to dispatch.
 159      *
 160      * Instead, the aio_poll calls include both the prepare and the
 161      * dispatch phase, hence a simple counter is enough for them.
 162      */
 163     uint32_t notify_me;
 164
 165     /* A lock to protect between QEMUBH and AioHandler adders and deleter,
 166      * and to ensure that no callbacks are removed while we're walking and
 167      * dispatching them.
 168      */
 169     QemuLockCnt list_lock;
 170
 171     /* Bottom Halves pending aio_bh_poll() processing */
 172     BHList bh_list;
 173
 174     /* Chained BH list slices for each nested aio_bh_poll() call */
 175     QSIMPLEQ_HEAD(, BHListSlice) bh_slice_list;
 176
 177     /* Used by aio_notify.
 178      *
 179      * "notified" is used to avoid expensive event_notifier_test_and_clear
 180      * calls.  When it is clear, the EventNotifier is clear, or one thread
 181      * is going to clear "notified" before processing more events.  False
 182      * positives are possible, i.e. "notified" could be set even though the
 183      * EventNotifier is clear.
 184      *
 185      * Note that event_notifier_set *cannot* be optimized the same way.  For
 186      * more information on the problem that would result, see "#ifdef BUG2"
 187      * in the docs/aio_notify_accept.promela formal model.
 188      */
 189     bool notified;
 190     EventNotifier notifier;
 191
 192     QSLIST_HEAD(, Coroutine) scheduled_coroutines;
 193     QEMUBH *co_schedule_bh;
 194
 195     /* Thread pool for performing work and receiving completion callbacks.
 196      * Has its own locking.
 197      */
 198     struct ThreadPool *thread_pool;
 199
 200 #ifdef CONFIG_LINUX_AIO
 201     /*
 202      * State for native Linux AIO.  Uses aio_context_acquire/release for
 203      * locking.
 204      */
 205     struct LinuxAioState *linux_aio;
 206 #endif
 207 #ifdef CONFIG_LINUX_IO_URING
 208     /*
 209      * State for Linux io_uring.  Uses aio_context_acquire/release for
 210      * locking.
 211      */
 212     struct LuringState *linux_io_uring;
 213
 214     /* State for file descriptor monitoring using Linux io_uring */
 215     struct io_uring fdmon_io_uring;
 216     AioHandlerSList submit_list;
 217 #endif
 218
 219     /* TimerLists for calling timers - one per clock type.  Has its own
 220      * locking.
 221      */
 222     QEMUTimerListGroup tlg;
 223
 224     int external_disable_cnt;
 225
 226     /* Number of AioHandlers without .io_poll() */
 227     int poll_disable_cnt;
 228
 229     /* Polling mode parameters */
 230     int64_t poll_ns;        /* current polling time in nanoseconds */
 231     int64_t poll_max_ns;    /* maximum polling time in nanoseconds */
 232     int64_t poll_grow;      /* polling time growth factor */
 233     int64_t poll_shrink;    /* polling time shrink factor */
 234
 235     /* AIO engine parameters */
 236     int64_t aio_max_batch;  /* maximum number of requests in a batch */
 237
 238     /*
 239      * List of handlers participating in userspace polling.  Protected by
 240      * ctx->list_lock.  Iterated and modified mostly by the event loop thread
 241      * from aio_poll() with ctx->list_lock incremented.  aio_set_fd_handler()
 242      * only touches the list to delete nodes if ctx->list_lock's count is zero.
 243      */
 244     AioHandlerList poll_aio_handlers;
 245
 246     /* Are we in polling mode or monitoring file descriptors? */
 247     bool poll_started;
 248
 249     /* epoll(7) state used when built with CONFIG_EPOLL */
 250     int epollfd;
 251
 252     const FDMonOps *fdmon_ops;
 253 };
 254
 255 /**
 256  * aio_context_new: Allocate a new AioContext.
 257  *
 258  * AioContext provide a mini event-loop that can be waited on synchronously.
 259  * They also provide bottom halves, a service to execute a piece of code
 260  * as soon as possible.
 261  */
 262 AioContext *aio_context_new(Error **errp);
 263
 264 /**
 265  * aio_context_ref:
 266  * @ctx: The AioContext to operate on.
 267  *
 268  * Add a reference to an AioContext.
 269  */
 270 void aio_context_ref(AioContext *ctx);
 271
 272 /**
 273  * aio_context_unref:
 274  * @ctx: The AioContext to operate on.
 275  *
 276  * Drop a reference to an AioContext.
 277  */
 278 void aio_context_unref(AioContext *ctx);
 279
 280 /* Take ownership of the AioContext.  If the AioContext will be shared between
 281  * threads, and a thread does not want to be interrupted, it will have to
 282  * take ownership around calls to aio_poll().  Otherwise, aio_poll()
 283  * automatically takes care of calling aio_context_acquire and
 284  * aio_context_release.
 285  *
 286  * Note that this is separate from bdrv_drained_begin/bdrv_drained_end.  A
 287  * thread still has to call those to avoid being interrupted by the guest.
 288  *
 289  * Bottom halves, timers and callbacks can be created or removed without
 290  * acquiring the AioContext.
 291  */
 292 void aio_context_acquire(AioContext *ctx);
 293
 294 /* Relinquish ownership of the AioContext. */
 295 void aio_context_release(AioContext *ctx);
 296
 297 /**
 298  * aio_bh_schedule_oneshot_full: Allocate a new bottom half structure that will
 299  * run only once and as soon as possible.
 300  *
 301  * @name: A human-readable identifier for debugging purposes.
 302  */
 303 void aio_bh_schedule_oneshot_full(AioContext *ctx, QEMUBHFunc *cb, void *opaque,
 304                                   const char *name);
 305
 306 /**
 307  * aio_bh_schedule_oneshot: Allocate a new bottom half structure that will run
 308  * only once and as soon as possible.
 309  *
 310  * A convenience wrapper for aio_bh_schedule_oneshot_full() that uses cb as the
 311  * name string.
 312  */
 313 #define aio_bh_schedule_oneshot(ctx, cb, opaque) \
 314     aio_bh_schedule_oneshot_full((ctx), (cb), (opaque), (stringify(cb)))
 315
 316 /**
 317  * aio_bh_new_full: Allocate a new bottom half structure.
 318  *
 319  * Bottom halves are lightweight callbacks whose invocation is guaranteed
 320  * to be wait-free, thread-safe and signal-safe.  The #QEMUBH structure
 321  * is opaque and must be allocated prior to its use.
 322  *
 323  * @name: A human-readable identifier for debugging purposes.
 324  */
 325 QEMUBH *aio_bh_new_full(AioContext *ctx, QEMUBHFunc *cb, void *opaque,
 326                         const char *name);
 327
 328 /**
 329  * aio_bh_new: Allocate a new bottom half structure
 330  *
 331  * A convenience wrapper for aio_bh_new_full() that uses the cb as the name
 332  * string.
 333  */
 334 #define aio_bh_new(ctx, cb, opaque) \
 335     aio_bh_new_full((ctx), (cb), (opaque), (stringify(cb)))
 336
 337 /**
 338  * aio_notify: Force processing of pending events.
 339  *
 340  * Similar to signaling a condition variable, aio_notify forces
 341  * aio_poll to exit, so that the next call will re-examine pending events.
 342  * The caller of aio_notify will usually call aio_poll again very soon,
 343  * or go through another iteration of the GLib main loop.  Hence, aio_notify
 344  * also has the side effect of recalculating the sets of file descriptors
 345  * that the main loop waits for.
 346  *
 347  * Calling aio_notify is rarely necessary, because for example scheduling
 348  * a bottom half calls it already.
 349  */
 350 void aio_notify(AioContext *ctx);
 351
 352 /**
 353  * aio_notify_accept: Acknowledge receiving an aio_notify.
 354  *
 355  * aio_notify() uses an EventNotifier in order to wake up a sleeping
 356  * aio_poll() or g_main_context_iteration().  Calls to aio_notify() are
 357  * usually rare, but the AioContext has to clear the EventNotifier on
 358  * every aio_poll() or g_main_context_iteration() in order to avoid
 359  * busy waiting.  This event_notifier_test_and_clear() cannot be done
 360  * using the usual aio_context_set_event_notifier(), because it must
 361  * be done before processing all events (file descriptors, bottom halves,
 362  * timers).
 363  *
 364  * aio_notify_accept() is an optimized event_notifier_test_and_clear()
 365  * that is specific to an AioContext's notifier; it is used internally
 366  * to clear the EventNotifier only if aio_notify() had been called.
 367  */
 368 void aio_notify_accept(AioContext *ctx);
 369
 370 /**
 371  * aio_bh_call: Executes callback function of the specified BH.
 372  */
 373 void aio_bh_call(QEMUBH *bh);
 374
 375 /**
 376  * aio_bh_poll: Poll bottom halves for an AioContext.
 377  *
 378  * These are internal functions used by the QEMU main loop.
 379  * And notice that multiple occurrences of aio_bh_poll cannot
 380  * be called concurrently
 381  */
 382 int aio_bh_poll(AioContext *ctx);
 383
 384 /**
 385  * qemu_bh_schedule: Schedule a bottom half.
 386  *
 387  * Scheduling a bottom half interrupts the main loop and causes the
 388  * execution of the callback that was passed to qemu_bh_new.
 389  *
 390  * Bottom halves that are scheduled from a bottom half handler are instantly
 391  * invoked.  This can create an infinite loop if a bottom half handler
 392  * schedules itself.
 393  *
 394  * @bh: The bottom half to be scheduled.
 395  */
 396 void qemu_bh_schedule(QEMUBH *bh);
 397
 398 /**
 399  * qemu_bh_cancel: Cancel execution of a bottom half.
 400  *
 401  * Canceling execution of a bottom half undoes the effect of calls to
 402  * qemu_bh_schedule without freeing its resources yet.  While cancellation
 403  * itself is also wait-free and thread-safe, it can of course race with the
 404  * loop that executes bottom halves unless you are holding the iothread
 405  * mutex.  This makes it mostly useless if you are not holding the mutex.
 406  *
 407  * @bh: The bottom half to be canceled.
 408  */
 409 void qemu_bh_cancel(QEMUBH *bh);
 410
 411 /**
 412  *qemu_bh_delete: Cancel execution of a bottom half and free its resources.
 413  *
 414  * Deleting a bottom half frees the memory that was allocated for it by
 415  * qemu_bh_new.  It also implies canceling the bottom half if it was
 416  * scheduled.
 417  * This func is async. The bottom half will do the delete action at the finial
 418  * end.
 419  *
 420  * @bh: The bottom half to be deleted.
 421  */
 422 void qemu_bh_delete(QEMUBH *bh);
 423
 424 /* Return whether there are any pending callbacks from the GSource
 425  * attached to the AioContext, before g_poll is invoked.
 426  *
 427  * This is used internally in the implementation of the GSource.
 428  */
 429 bool aio_prepare(AioContext *ctx);
 430
 431 /* Return whether there are any pending callbacks from the GSource
 432  * attached to the AioContext, after g_poll is invoked.
 433  *
 434  * This is used internally in the implementation of the GSource.
 435  */
 436 bool aio_pending(AioContext *ctx);
 437
 438 /* Dispatch any pending callbacks from the GSource attached to the AioContext.
 439  *
 440  * This is used internally in the implementation of the GSource.
 441  */
 442 void aio_dispatch(AioContext *ctx);
 443
 444 /* Progress in completing AIO work to occur.  This can issue new pending
 445  * aio as a result of executing I/O completion or bh callbacks.
 446  *
 447  * Return whether any progress was made by executing AIO or bottom half
 448  * handlers.  If @blocking == true, this should always be true except
 449  * if someone called aio_notify.
 450  *
 451  * If there are no pending bottom halves, but there are pending AIO
 452  * operations, it may not be possible to make any progress without
 453  * blocking.  If @blocking is true, this function will wait until one
 454  * or more AIO events have completed, to ensure something has moved
 455  * before returning.
 456  */
 457 bool aio_poll(AioContext *ctx, bool blocking);
 458
 459 /* Register a file descriptor and associated callbacks.  Behaves very similarly
 460  * to qemu_set_fd_handler.  Unlike qemu_set_fd_handler, these callbacks will
 461  * be invoked when using aio_poll().
 462  *
 463  * Code that invokes AIO completion functions should rely on this function
 464  * instead of qemu_set_fd_handler[2].
 465  */
 466 void aio_set_fd_handler(AioContext *ctx,
 467                         int fd,
 468                         bool is_external,
 469                         IOHandler *io_read,
 470                         IOHandler *io_write,
 471                         AioPollFn *io_poll,
 472                         IOHandler *io_poll_ready,
 473                         void *opaque);
 474
 475 /* Set polling begin/end callbacks for a file descriptor that has already been
 476  * registered with aio_set_fd_handler.  Do nothing if the file descriptor is
 477  * not registered.
 478  */
 479 void aio_set_fd_poll(AioContext *ctx, int fd,
 480                      IOHandler *io_poll_begin,
 481                      IOHandler *io_poll_end);
 482
 483 /* Register an event notifier and associated callbacks.  Behaves very similarly
 484  * to event_notifier_set_handler.  Unlike event_notifier_set_handler, these callbacks
 485  * will be invoked when using aio_poll().
 486  *
 487  * Code that invokes AIO completion functions should rely on this function
 488  * instead of event_notifier_set_handler.
 489  */
 490 void aio_set_event_notifier(AioContext *ctx,
 491                             EventNotifier *notifier,
 492                             bool is_external,
 493                             EventNotifierHandler *io_read,
 494                             AioPollFn *io_poll,
 495                             EventNotifierHandler *io_poll_ready);
 496
 497 /* Set polling begin/end callbacks for an event notifier that has already been
 498  * registered with aio_set_event_notifier.  Do nothing if the event notifier is
 499  * not registered.
 500  */
 501 void aio_set_event_notifier_poll(AioContext *ctx,
 502                                  EventNotifier *notifier,
 503                                  EventNotifierHandler *io_poll_begin,
 504                                  EventNotifierHandler *io_poll_end);
 505
 506 /* Return a GSource that lets the main loop poll the file descriptors attached
 507  * to this AioContext.
 508  */
 509 GSource *aio_get_g_source(AioContext *ctx);
 510
 511 /* Return the ThreadPool bound to this AioContext */
 512 struct ThreadPool *aio_get_thread_pool(AioContext *ctx);
 513
 514 /* Setup the LinuxAioState bound to this AioContext */
 515 struct LinuxAioState *aio_setup_linux_aio(AioContext *ctx, Error **errp);
 516
 517 /* Return the LinuxAioState bound to this AioContext */
 518 struct LinuxAioState *aio_get_linux_aio(AioContext *ctx);
 519
 520 /* Setup the LuringState bound to this AioContext */
 521 struct LuringState *aio_setup_linux_io_uring(AioContext *ctx, Error **errp);
 522
 523 /* Return the LuringState bound to this AioContext */
 524 struct LuringState *aio_get_linux_io_uring(AioContext *ctx);
 525 /**
 526  * aio_timer_new_with_attrs:
 527  * @ctx: the aio context
 528  * @type: the clock type
 529  * @scale: the scale
 530  * @attributes: 0, or one to multiple OR'ed QEMU_TIMER_ATTR_<id> values
 531  *              to assign
 532  * @cb: the callback to call on timer expiry
 533  * @opaque: the opaque pointer to pass to the callback
 534  *
 535  * Allocate a new timer (with attributes) attached to the context @ctx.
 536  * The function is responsible for memory allocation.
 537  *
 538  * The preferred interface is aio_timer_init or aio_timer_init_with_attrs.
 539  * Use that unless you really need dynamic memory allocation.
 540  *
 541  * Returns: a pointer to the new timer
 542  */
 543 static inline QEMUTimer *aio_timer_new_with_attrs(AioContext *ctx,
 544                                                   QEMUClockType type,
 545                                                   int scale, int attributes,
 546                                                   QEMUTimerCB *cb, void *opaque)
 547 {
 548     return timer_new_full(&ctx->tlg, type, scale, attributes, cb, opaque);
 549 }
 550
 551 /**
 552  * aio_timer_new:
 553  * @ctx: the aio context
 554  * @type: the clock type
 555  * @scale: the scale
 556  * @cb: the callback to call on timer expiry
 557  * @opaque: the opaque pointer to pass to the callback
 558  *
 559  * Allocate a new timer attached to the context @ctx.
 560  * See aio_timer_new_with_attrs for details.
 561  *
 562  * Returns: a pointer to the new timer
 563  */
 564 static inline QEMUTimer *aio_timer_new(AioContext *ctx, QEMUClockType type,
 565                                        int scale,
 566                                        QEMUTimerCB *cb, void *opaque)
 567 {
 568     return timer_new_full(&ctx->tlg, type, scale, 0, cb, opaque);
 569 }
 570
 571 /**
 572  * aio_timer_init_with_attrs:
 573  * @ctx: the aio context
 574  * @ts: the timer
 575  * @type: the clock type
 576  * @scale: the scale
 577  * @attributes: 0, or one to multiple OR'ed QEMU_TIMER_ATTR_<id> values
 578  *              to assign
 579  * @cb: the callback to call on timer expiry
 580  * @opaque: the opaque pointer to pass to the callback
 581  *
 582  * Initialise a new timer (with attributes) attached to the context @ctx.
 583  * The caller is responsible for memory allocation.
 584  */
 585 static inline void aio_timer_init_with_attrs(AioContext *ctx,
 586                                              QEMUTimer *ts, QEMUClockType type,
 587                                              int scale, int attributes,
 588                                              QEMUTimerCB *cb, void *opaque)
 589 {
 590     timer_init_full(ts, &ctx->tlg, type, scale, attributes, cb, opaque);
 591 }
 592
 593 /**
 594  * aio_timer_init:
 595  * @ctx: the aio context
 596  * @ts: the timer
 597  * @type: the clock type
 598  * @scale: the scale
 599  * @cb: the callback to call on timer expiry
 600  * @opaque: the opaque pointer to pass to the callback
 601  *
 602  * Initialise a new timer attached to the context @ctx.
 603  * See aio_timer_init_with_attrs for details.
 604  */
 605 static inline void aio_timer_init(AioContext *ctx,
 606                                   QEMUTimer *ts, QEMUClockType type,
 607                                   int scale,
 608                                   QEMUTimerCB *cb, void *opaque)
 609 {
 610     timer_init_full(ts, &ctx->tlg, type, scale, 0, cb, opaque);
 611 }
 612
 613 /**
 614  * aio_compute_timeout:
 615  * @ctx: the aio context
 616  *
 617  * Compute the timeout that a blocking aio_poll should use.
 618  */
 619 int64_t aio_compute_timeout(AioContext *ctx);
 620
 621 /**
 622  * aio_disable_external:
 623  * @ctx: the aio context
 624  *
 625  * Disable the further processing of external clients.
 626  */
 627 static inline void aio_disable_external(AioContext *ctx)
 628 {
 629     qatomic_inc(&ctx->external_disable_cnt);
 630 }
 631
 632 /**
 633  * aio_enable_external:
 634  * @ctx: the aio context
 635  *
 636  * Enable the processing of external clients.
 637  */
 638 static inline void aio_enable_external(AioContext *ctx)
 639 {
 640     int old;
 641
 642     old = qatomic_fetch_dec(&ctx->external_disable_cnt);
 643     assert(old > 0);
 644     if (old == 1) {
 645         /* Kick event loop so it re-arms file descriptors */
 646         aio_notify(ctx);
 647     }
 648 }
 649
 650 /**
 651  * aio_external_disabled:
 652  * @ctx: the aio context
 653  *
 654  * Return true if the external clients are disabled.
 655  */
 656 static inline bool aio_external_disabled(AioContext *ctx)
 657 {
 658     return qatomic_read(&ctx->external_disable_cnt);
 659 }
 660
 661 /**
 662  * aio_node_check:
 663  * @ctx: the aio context
 664  * @is_external: Whether or not the checked node is an external event source.
 665  *
 666  * Check if the node's is_external flag is okay to be polled by the ctx at this
 667  * moment. True means green light.
 668  */
 669 static inline bool aio_node_check(AioContext *ctx, bool is_external)
 670 {
 671     return !is_external || !qatomic_read(&ctx->external_disable_cnt);
 672 }
 673
 674 /**
 675  * aio_co_schedule:
 676  * @ctx: the aio context
 677  * @co: the coroutine
 678  *
 679  * Start a coroutine on a remote AioContext.
 680  *
 681  * The coroutine must not be entered by anyone else while aio_co_schedule()
 682  * is active.  In addition the coroutine must have yielded unless ctx
 683  * is the context in which the coroutine is running (i.e. the value of
 684  * qemu_get_current_aio_context() from the coroutine itself).
 685  */
 686 void aio_co_schedule(AioContext *ctx, struct Coroutine *co);
 687
 688 /**
 689  * aio_co_reschedule_self:
 690  * @new_ctx: the new context
 691  *
 692  * Move the currently running coroutine to new_ctx. If the coroutine is already
 693  * running in new_ctx, do nothing.
 694  */
 695 void coroutine_fn aio_co_reschedule_self(AioContext *new_ctx);
 696
 697 /**
 698  * aio_co_wake:
 699  * @co: the coroutine
 700  *
 701  * Restart a coroutine on the AioContext where it was running last, thus
 702  * preventing coroutines from jumping from one context to another when they
 703  * go to sleep.
 704  *
 705  * aio_co_wake may be executed either in coroutine or non-coroutine
 706  * context.  The coroutine must not be entered by anyone else while
 707  * aio_co_wake() is active.
 708  */
 709 void aio_co_wake(struct Coroutine *co);
 710
 711 /**
 712  * aio_co_enter:
 713  * @ctx: the context to run the coroutine
 714  * @co: the coroutine to run
 715  *
 716  * Enter a coroutine in the specified AioContext.
 717  */
 718 void aio_co_enter(AioContext *ctx, struct Coroutine *co);
 719
 720 /**
 721  * Return the AioContext whose event loop runs in the current thread.
 722  *
 723  * If called from an IOThread this will be the IOThread's AioContext.  If
 724  * called from the main thread or with the "big QEMU lock" taken it
 725  * will be the main loop AioContext.
 726  */
 727 AioContext *qemu_get_current_aio_context(void);
 728
 729 void qemu_set_current_aio_context(AioContext *ctx);
 730
 731 /**
 732  * aio_context_setup:
 733  * @ctx: the aio context
 734  *
 735  * Initialize the aio context.
 736  */
 737 void aio_context_setup(AioContext *ctx);
 738
 739 /**
 740  * aio_context_destroy:
 741  * @ctx: the aio context
 742  *
 743  * Destroy the aio context.
 744  */
 745 void aio_context_destroy(AioContext *ctx);
 746
 747 /* Used internally, do not call outside AioContext code */
 748 void aio_context_use_g_source(AioContext *ctx);
 749
 750 /**
 751  * aio_context_set_poll_params:
 752  * @ctx: the aio context
 753  * @max_ns: how long to busy poll for, in nanoseconds
 754  * @grow: polling time growth factor
 755  * @shrink: polling time shrink factor
 756  *
 757  * Poll mode can be disabled by setting poll_max_ns to 0.
 758  */
 759 void aio_context_set_poll_params(AioContext *ctx, int64_t max_ns,
 760                                  int64_t grow, int64_t shrink,
 761                                  Error **errp);
 762
 763 /**
 764  * aio_context_set_aio_params:
 765  * @ctx: the aio context
 766  * @max_batch: maximum number of requests in a batch, 0 means that the
 767  *             engine will use its default
 768  */
 769 void aio_context_set_aio_params(AioContext *ctx, int64_t max_batch,
 770                                 Error **errp);
 771
 772 #endif