xref: /openbmc/qemu/include/block/aio.h (revision e669e800)
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-core.h"
21 #include "qemu/queue.h"
22 #include "qemu/event_notifier.h"
23 #include "qemu/thread.h"
24 #include "qemu/timer.h"
25 #include "block/graph-lock.h"
26 #include "hw/qdev-core.h"
27 
28 
29 typedef struct BlockAIOCB BlockAIOCB;
30 typedef void BlockCompletionFunc(void *opaque, int ret);
31 
32 typedef struct AIOCBInfo {
33     void (*cancel_async)(BlockAIOCB *acb);
34     size_t aiocb_size;
35 } AIOCBInfo;
36 
37 struct BlockAIOCB {
38     const AIOCBInfo *aiocb_info;
39     BlockDriverState *bs;
40     BlockCompletionFunc *cb;
41     void *opaque;
42     int refcnt;
43 };
44 
45 void *qemu_aio_get(const AIOCBInfo *aiocb_info, BlockDriverState *bs,
46                    BlockCompletionFunc *cb, void *opaque);
47 void qemu_aio_unref(void *p);
48 void qemu_aio_ref(void *p);
49 
50 typedef struct AioHandler AioHandler;
51 typedef QLIST_HEAD(, AioHandler) AioHandlerList;
52 typedef void QEMUBHFunc(void *opaque);
53 typedef bool AioPollFn(void *opaque);
54 typedef void IOHandler(void *opaque);
55 
56 struct ThreadPool;
57 struct LinuxAioState;
58 typedef struct LuringState LuringState;
59 
60 /* Is polling disabled? */
61 bool aio_poll_disabled(AioContext *ctx);
62 
63 /* Callbacks for file descriptor monitoring implementations */
64 typedef struct {
65     /*
66      * update:
67      * @ctx: the AioContext
68      * @old_node: the existing handler or NULL if this file descriptor is being
69      *            monitored for the first time
70      * @new_node: the new handler or NULL if this file descriptor is being
71      *            removed
72      *
73      * Add/remove/modify a monitored file descriptor.
74      *
75      * Called with ctx->list_lock acquired.
76      */
77     void (*update)(AioContext *ctx, AioHandler *old_node, AioHandler *new_node);
78 
79     /*
80      * wait:
81      * @ctx: the AioContext
82      * @ready_list: list for handlers that become ready
83      * @timeout: maximum duration to wait, in nanoseconds
84      *
85      * Wait for file descriptors to become ready and place them on ready_list.
86      *
87      * Called with ctx->list_lock incremented but not locked.
88      *
89      * Returns: number of ready file descriptors.
90      */
91     int (*wait)(AioContext *ctx, AioHandlerList *ready_list, int64_t timeout);
92 
93     /*
94      * need_wait:
95      * @ctx: the AioContext
96      *
97      * Tell aio_poll() when to stop userspace polling early because ->wait()
98      * has fds ready.
99      *
100      * File descriptor monitoring implementations that cannot poll fd readiness
101      * from userspace should use aio_poll_disabled() here.  This ensures that
102      * file descriptors are not starved by handlers that frequently make
103      * progress via userspace polling.
104      *
105      * Returns: true if ->wait() should be called, false otherwise.
106      */
107     bool (*need_wait)(AioContext *ctx);
108 } FDMonOps;
109 
110 /*
111  * Each aio_bh_poll() call carves off a slice of the BH list, so that newly
112  * scheduled BHs are not processed until the next aio_bh_poll() call.  All
113  * active aio_bh_poll() calls chain their slices together in a list, so that
114  * nested aio_bh_poll() calls process all scheduled bottom halves.
115  */
116 typedef QSLIST_HEAD(, QEMUBH) BHList;
117 typedef struct BHListSlice BHListSlice;
118 struct BHListSlice {
119     BHList bh_list;
120     QSIMPLEQ_ENTRY(BHListSlice) next;
121 };
122 
123 typedef QSLIST_HEAD(, AioHandler) AioHandlerSList;
124 
125 struct AioContext {
126     GSource source;
127 
128     /* Used by AioContext users to protect from multi-threaded access.  */
129     QemuRecMutex lock;
130 
131     /*
132      * Keep track of readers and writers of the block layer graph.
133      * This is essential to avoid performing additions and removal
134      * of nodes and edges from block graph while some
135      * other thread is traversing it.
136      */
137     BdrvGraphRWlock *bdrv_graph;
138 
139     /* The list of registered AIO handlers.  Protected by ctx->list_lock. */
140     AioHandlerList aio_handlers;
141 
142     /* The list of AIO handlers to be deleted.  Protected by ctx->list_lock. */
143     AioHandlerList deleted_aio_handlers;
144 
145     /* Used to avoid unnecessary event_notifier_set calls in aio_notify;
146      * only written from the AioContext home thread, or under the BQL in
147      * the case of the main AioContext.  However, it is read from any
148      * thread so it is still accessed with atomic primitives.
149      *
150      * If this field is 0, everything (file descriptors, bottom halves,
151      * timers) will be re-evaluated before the next blocking poll() or
152      * io_uring wait; therefore, the event_notifier_set call can be
153      * skipped.  If it is non-zero, you may need to wake up a concurrent
154      * aio_poll or the glib main event loop, making event_notifier_set
155      * necessary.
156      *
157      * Bit 0 is reserved for GSource usage of the AioContext, and is 1
158      * between a call to aio_ctx_prepare and the next call to aio_ctx_check.
159      * Bits 1-31 simply count the number of active calls to aio_poll
160      * that are in the prepare or poll phase.
161      *
162      * The GSource and aio_poll must use a different mechanism because
163      * there is no certainty that a call to GSource's prepare callback
164      * (via g_main_context_prepare) is indeed followed by check and
165      * dispatch.  It's not clear whether this would be a bug, but let's
166      * play safe and allow it---it will just cause extra calls to
167      * event_notifier_set until the next call to dispatch.
168      *
169      * Instead, the aio_poll calls include both the prepare and the
170      * dispatch phase, hence a simple counter is enough for them.
171      */
172     uint32_t notify_me;
173 
174     /* A lock to protect between QEMUBH and AioHandler adders and deleter,
175      * and to ensure that no callbacks are removed while we're walking and
176      * dispatching them.
177      */
178     QemuLockCnt list_lock;
179 
180     /* Bottom Halves pending aio_bh_poll() processing */
181     BHList bh_list;
182 
183     /* Chained BH list slices for each nested aio_bh_poll() call */
184     QSIMPLEQ_HEAD(, BHListSlice) bh_slice_list;
185 
186     /* Used by aio_notify.
187      *
188      * "notified" is used to avoid expensive event_notifier_test_and_clear
189      * calls.  When it is clear, the EventNotifier is clear, or one thread
190      * is going to clear "notified" before processing more events.  False
191      * positives are possible, i.e. "notified" could be set even though the
192      * EventNotifier is clear.
193      *
194      * Note that event_notifier_set *cannot* be optimized the same way.  For
195      * more information on the problem that would result, see "#ifdef BUG2"
196      * in the docs/aio_notify_accept.promela formal model.
197      */
198     bool notified;
199     EventNotifier notifier;
200 
201     QSLIST_HEAD(, Coroutine) scheduled_coroutines;
202     QEMUBH *co_schedule_bh;
203 
204     int thread_pool_min;
205     int thread_pool_max;
206     /* Thread pool for performing work and receiving completion callbacks.
207      * Has its own locking.
208      */
209     struct ThreadPool *thread_pool;
210 
211 #ifdef CONFIG_LINUX_AIO
212     struct LinuxAioState *linux_aio;
213 #endif
214 #ifdef CONFIG_LINUX_IO_URING
215     LuringState *linux_io_uring;
216 
217     /* State for file descriptor monitoring using Linux io_uring */
218     struct io_uring fdmon_io_uring;
219     AioHandlerSList submit_list;
220 #endif
221 
222     /* TimerLists for calling timers - one per clock type.  Has its own
223      * locking.
224      */
225     QEMUTimerListGroup tlg;
226 
227     /* Number of AioHandlers without .io_poll() */
228     int poll_disable_cnt;
229 
230     /* Polling mode parameters */
231     int64_t poll_ns;        /* current polling time in nanoseconds */
232     int64_t poll_max_ns;    /* maximum polling time in nanoseconds */
233     int64_t poll_grow;      /* polling time growth factor */
234     int64_t poll_shrink;    /* polling time shrink factor */
235 
236     /* AIO engine parameters */
237     int64_t aio_max_batch;  /* maximum number of requests in a batch */
238 
239     /*
240      * List of handlers participating in userspace polling.  Protected by
241      * ctx->list_lock.  Iterated and modified mostly by the event loop thread
242      * from aio_poll() with ctx->list_lock incremented.  aio_set_fd_handler()
243      * only touches the list to delete nodes if ctx->list_lock's count is zero.
244      */
245     AioHandlerList poll_aio_handlers;
246 
247     /* Are we in polling mode or monitoring file descriptors? */
248     bool poll_started;
249 
250     /* epoll(7) state used when built with CONFIG_EPOLL */
251     int epollfd;
252 
253     const FDMonOps *fdmon_ops;
254 };
255 
256 /**
257  * aio_context_new: Allocate a new AioContext.
258  *
259  * AioContext provide a mini event-loop that can be waited on synchronously.
260  * They also provide bottom halves, a service to execute a piece of code
261  * as soon as possible.
262  */
263 AioContext *aio_context_new(Error **errp);
264 
265 /**
266  * aio_context_ref:
267  * @ctx: The AioContext to operate on.
268  *
269  * Add a reference to an AioContext.
270  */
271 void aio_context_ref(AioContext *ctx);
272 
273 /**
274  * aio_context_unref:
275  * @ctx: The AioContext to operate on.
276  *
277  * Drop a reference to an AioContext.
278  */
279 void aio_context_unref(AioContext *ctx);
280 
281 /**
282  * aio_bh_schedule_oneshot_full: Allocate a new bottom half structure that will
283  * run only once and as soon as possible.
284  *
285  * @name: A human-readable identifier for debugging purposes.
286  */
287 void aio_bh_schedule_oneshot_full(AioContext *ctx, QEMUBHFunc *cb, void *opaque,
288                                   const char *name);
289 
290 /**
291  * aio_bh_schedule_oneshot: Allocate a new bottom half structure that will run
292  * only once and as soon as possible.
293  *
294  * A convenience wrapper for aio_bh_schedule_oneshot_full() that uses cb as the
295  * name string.
296  */
297 #define aio_bh_schedule_oneshot(ctx, cb, opaque) \
298     aio_bh_schedule_oneshot_full((ctx), (cb), (opaque), (stringify(cb)))
299 
300 /**
301  * aio_bh_new_full: Allocate a new bottom half structure.
302  *
303  * Bottom halves are lightweight callbacks whose invocation is guaranteed
304  * to be wait-free, thread-safe and signal-safe.  The #QEMUBH structure
305  * is opaque and must be allocated prior to its use.
306  *
307  * @name: A human-readable identifier for debugging purposes.
308  * @reentrancy_guard: A guard set when entering a cb to prevent
309  * device-reentrancy issues
310  */
311 QEMUBH *aio_bh_new_full(AioContext *ctx, QEMUBHFunc *cb, void *opaque,
312                         const char *name, MemReentrancyGuard *reentrancy_guard);
313 
314 /**
315  * aio_bh_new: Allocate a new bottom half structure
316  *
317  * A convenience wrapper for aio_bh_new_full() that uses the cb as the name
318  * string.
319  */
320 #define aio_bh_new(ctx, cb, opaque) \
321     aio_bh_new_full((ctx), (cb), (opaque), (stringify(cb)), NULL)
322 
323 /**
324  * aio_bh_new_guarded: Allocate a new bottom half structure with a
325  * reentrancy_guard
326  *
327  * A convenience wrapper for aio_bh_new_full() that uses the cb as the name
328  * string.
329  */
330 #define aio_bh_new_guarded(ctx, cb, opaque, guard) \
331     aio_bh_new_full((ctx), (cb), (opaque), (stringify(cb)), guard)
332 
333 /**
334  * aio_notify: Force processing of pending events.
335  *
336  * Similar to signaling a condition variable, aio_notify forces
337  * aio_poll to exit, so that the next call will re-examine pending events.
338  * The caller of aio_notify will usually call aio_poll again very soon,
339  * or go through another iteration of the GLib main loop.  Hence, aio_notify
340  * also has the side effect of recalculating the sets of file descriptors
341  * that the main loop waits for.
342  *
343  * Calling aio_notify is rarely necessary, because for example scheduling
344  * a bottom half calls it already.
345  */
346 void aio_notify(AioContext *ctx);
347 
348 /**
349  * aio_notify_accept: Acknowledge receiving an aio_notify.
350  *
351  * aio_notify() uses an EventNotifier in order to wake up a sleeping
352  * aio_poll() or g_main_context_iteration().  Calls to aio_notify() are
353  * usually rare, but the AioContext has to clear the EventNotifier on
354  * every aio_poll() or g_main_context_iteration() in order to avoid
355  * busy waiting.  This event_notifier_test_and_clear() cannot be done
356  * using the usual aio_context_set_event_notifier(), because it must
357  * be done before processing all events (file descriptors, bottom halves,
358  * timers).
359  *
360  * aio_notify_accept() is an optimized event_notifier_test_and_clear()
361  * that is specific to an AioContext's notifier; it is used internally
362  * to clear the EventNotifier only if aio_notify() had been called.
363  */
364 void aio_notify_accept(AioContext *ctx);
365 
366 /**
367  * aio_bh_call: Executes callback function of the specified BH.
368  */
369 void aio_bh_call(QEMUBH *bh);
370 
371 /**
372  * aio_bh_poll: Poll bottom halves for an AioContext.
373  *
374  * These are internal functions used by the QEMU main loop.
375  * And notice that multiple occurrences of aio_bh_poll cannot
376  * be called concurrently
377  */
378 int aio_bh_poll(AioContext *ctx);
379 
380 /**
381  * qemu_bh_schedule: Schedule a bottom half.
382  *
383  * Scheduling a bottom half interrupts the main loop and causes the
384  * execution of the callback that was passed to qemu_bh_new.
385  *
386  * Bottom halves that are scheduled from a bottom half handler are instantly
387  * invoked.  This can create an infinite loop if a bottom half handler
388  * schedules itself.
389  *
390  * @bh: The bottom half to be scheduled.
391  */
392 void qemu_bh_schedule(QEMUBH *bh);
393 
394 /**
395  * qemu_bh_cancel: Cancel execution of a bottom half.
396  *
397  * Canceling execution of a bottom half undoes the effect of calls to
398  * qemu_bh_schedule without freeing its resources yet.  While cancellation
399  * itself is also wait-free and thread-safe, it can of course race with the
400  * loop that executes bottom halves unless you are holding the iothread
401  * mutex.  This makes it mostly useless if you are not holding the mutex.
402  *
403  * @bh: The bottom half to be canceled.
404  */
405 void qemu_bh_cancel(QEMUBH *bh);
406 
407 /**
408  *qemu_bh_delete: Cancel execution of a bottom half and free its resources.
409  *
410  * Deleting a bottom half frees the memory that was allocated for it by
411  * qemu_bh_new.  It also implies canceling the bottom half if it was
412  * scheduled.
413  * This func is async. The bottom half will do the delete action at the finial
414  * end.
415  *
416  * @bh: The bottom half to be deleted.
417  */
418 void qemu_bh_delete(QEMUBH *bh);
419 
420 /* Return whether there are any pending callbacks from the GSource
421  * attached to the AioContext, before g_poll is invoked.
422  *
423  * This is used internally in the implementation of the GSource.
424  */
425 bool aio_prepare(AioContext *ctx);
426 
427 /* Return whether there are any pending callbacks from the GSource
428  * attached to the AioContext, after g_poll is invoked.
429  *
430  * This is used internally in the implementation of the GSource.
431  */
432 bool aio_pending(AioContext *ctx);
433 
434 /* Dispatch any pending callbacks from the GSource attached to the AioContext.
435  *
436  * This is used internally in the implementation of the GSource.
437  */
438 void aio_dispatch(AioContext *ctx);
439 
440 /* Progress in completing AIO work to occur.  This can issue new pending
441  * aio as a result of executing I/O completion or bh callbacks.
442  *
443  * Return whether any progress was made by executing AIO or bottom half
444  * handlers.  If @blocking == true, this should always be true except
445  * if someone called aio_notify.
446  *
447  * If there are no pending bottom halves, but there are pending AIO
448  * operations, it may not be possible to make any progress without
449  * blocking.  If @blocking is true, this function will wait until one
450  * or more AIO events have completed, to ensure something has moved
451  * before returning.
452  */
453 bool no_coroutine_fn aio_poll(AioContext *ctx, bool blocking);
454 
455 /* Register a file descriptor and associated callbacks.  Behaves very similarly
456  * to qemu_set_fd_handler.  Unlike qemu_set_fd_handler, these callbacks will
457  * be invoked when using aio_poll().
458  *
459  * Code that invokes AIO completion functions should rely on this function
460  * instead of qemu_set_fd_handler[2].
461  */
462 void aio_set_fd_handler(AioContext *ctx,
463                         int fd,
464                         IOHandler *io_read,
465                         IOHandler *io_write,
466                         AioPollFn *io_poll,
467                         IOHandler *io_poll_ready,
468                         void *opaque);
469 
470 /* Register an event notifier and associated callbacks.  Behaves very similarly
471  * to event_notifier_set_handler.  Unlike event_notifier_set_handler, these callbacks
472  * will be invoked when using aio_poll().
473  *
474  * Code that invokes AIO completion functions should rely on this function
475  * instead of event_notifier_set_handler.
476  */
477 void aio_set_event_notifier(AioContext *ctx,
478                             EventNotifier *notifier,
479                             EventNotifierHandler *io_read,
480                             AioPollFn *io_poll,
481                             EventNotifierHandler *io_poll_ready);
482 
483 /*
484  * Set polling begin/end callbacks for an event notifier that has already been
485  * registered with aio_set_event_notifier.  Do nothing if the event notifier is
486  * not registered.
487  *
488  * Note that if the io_poll_end() callback (or the entire notifier) is removed
489  * during polling, it will not be called, so an io_poll_begin() is not
490  * necessarily always followed by an io_poll_end().
491  */
492 void aio_set_event_notifier_poll(AioContext *ctx,
493                                  EventNotifier *notifier,
494                                  EventNotifierHandler *io_poll_begin,
495                                  EventNotifierHandler *io_poll_end);
496 
497 /* Return a GSource that lets the main loop poll the file descriptors attached
498  * to this AioContext.
499  */
500 GSource *aio_get_g_source(AioContext *ctx);
501 
502 /* Return the ThreadPool bound to this AioContext */
503 struct ThreadPool *aio_get_thread_pool(AioContext *ctx);
504 
505 /* Setup the LinuxAioState bound to this AioContext */
506 struct LinuxAioState *aio_setup_linux_aio(AioContext *ctx, Error **errp);
507 
508 /* Return the LinuxAioState bound to this AioContext */
509 struct LinuxAioState *aio_get_linux_aio(AioContext *ctx);
510 
511 /* Setup the LuringState bound to this AioContext */
512 LuringState *aio_setup_linux_io_uring(AioContext *ctx, Error **errp);
513 
514 /* Return the LuringState bound to this AioContext */
515 LuringState *aio_get_linux_io_uring(AioContext *ctx);
516 /**
517  * aio_timer_new_with_attrs:
518  * @ctx: the aio context
519  * @type: the clock type
520  * @scale: the scale
521  * @attributes: 0, or one to multiple OR'ed QEMU_TIMER_ATTR_<id> values
522  *              to assign
523  * @cb: the callback to call on timer expiry
524  * @opaque: the opaque pointer to pass to the callback
525  *
526  * Allocate a new timer (with attributes) attached to the context @ctx.
527  * The function is responsible for memory allocation.
528  *
529  * The preferred interface is aio_timer_init or aio_timer_init_with_attrs.
530  * Use that unless you really need dynamic memory allocation.
531  *
532  * Returns: a pointer to the new timer
533  */
aio_timer_new_with_attrs(AioContext * ctx,QEMUClockType type,int scale,int attributes,QEMUTimerCB * cb,void * opaque)534 static inline QEMUTimer *aio_timer_new_with_attrs(AioContext *ctx,
535                                                   QEMUClockType type,
536                                                   int scale, int attributes,
537                                                   QEMUTimerCB *cb, void *opaque)
538 {
539     return timer_new_full(&ctx->tlg, type, scale, attributes, cb, opaque);
540 }
541 
542 /**
543  * aio_timer_new:
544  * @ctx: the aio context
545  * @type: the clock type
546  * @scale: the scale
547  * @cb: the callback to call on timer expiry
548  * @opaque: the opaque pointer to pass to the callback
549  *
550  * Allocate a new timer attached to the context @ctx.
551  * See aio_timer_new_with_attrs for details.
552  *
553  * Returns: a pointer to the new timer
554  */
aio_timer_new(AioContext * ctx,QEMUClockType type,int scale,QEMUTimerCB * cb,void * opaque)555 static inline QEMUTimer *aio_timer_new(AioContext *ctx, QEMUClockType type,
556                                        int scale,
557                                        QEMUTimerCB *cb, void *opaque)
558 {
559     return timer_new_full(&ctx->tlg, type, scale, 0, cb, opaque);
560 }
561 
562 /**
563  * aio_timer_init_with_attrs:
564  * @ctx: the aio context
565  * @ts: the timer
566  * @type: the clock type
567  * @scale: the scale
568  * @attributes: 0, or one to multiple OR'ed QEMU_TIMER_ATTR_<id> values
569  *              to assign
570  * @cb: the callback to call on timer expiry
571  * @opaque: the opaque pointer to pass to the callback
572  *
573  * Initialise a new timer (with attributes) attached to the context @ctx.
574  * The caller is responsible for memory allocation.
575  */
aio_timer_init_with_attrs(AioContext * ctx,QEMUTimer * ts,QEMUClockType type,int scale,int attributes,QEMUTimerCB * cb,void * opaque)576 static inline void aio_timer_init_with_attrs(AioContext *ctx,
577                                              QEMUTimer *ts, QEMUClockType type,
578                                              int scale, int attributes,
579                                              QEMUTimerCB *cb, void *opaque)
580 {
581     timer_init_full(ts, &ctx->tlg, type, scale, attributes, cb, opaque);
582 }
583 
584 /**
585  * aio_timer_init:
586  * @ctx: the aio context
587  * @ts: the timer
588  * @type: the clock type
589  * @scale: the scale
590  * @cb: the callback to call on timer expiry
591  * @opaque: the opaque pointer to pass to the callback
592  *
593  * Initialise a new timer attached to the context @ctx.
594  * See aio_timer_init_with_attrs for details.
595  */
aio_timer_init(AioContext * ctx,QEMUTimer * ts,QEMUClockType type,int scale,QEMUTimerCB * cb,void * opaque)596 static inline void aio_timer_init(AioContext *ctx,
597                                   QEMUTimer *ts, QEMUClockType type,
598                                   int scale,
599                                   QEMUTimerCB *cb, void *opaque)
600 {
601     timer_init_full(ts, &ctx->tlg, type, scale, 0, cb, opaque);
602 }
603 
604 /**
605  * aio_compute_timeout:
606  * @ctx: the aio context
607  *
608  * Compute the timeout that a blocking aio_poll should use.
609  */
610 int64_t aio_compute_timeout(AioContext *ctx);
611 
612 /**
613  * aio_co_schedule:
614  * @ctx: the aio context
615  * @co: the coroutine
616  *
617  * Start a coroutine on a remote AioContext.
618  *
619  * The coroutine must not be entered by anyone else while aio_co_schedule()
620  * is active.  In addition the coroutine must have yielded unless ctx
621  * is the context in which the coroutine is running (i.e. the value of
622  * qemu_get_current_aio_context() from the coroutine itself).
623  */
624 void aio_co_schedule(AioContext *ctx, Coroutine *co);
625 
626 /**
627  * aio_co_reschedule_self:
628  * @new_ctx: the new context
629  *
630  * Move the currently running coroutine to new_ctx. If the coroutine is already
631  * running in new_ctx, do nothing.
632  *
633  * Note that this function cannot reschedule from iohandler_ctx to
634  * qemu_aio_context.
635  */
636 void coroutine_fn aio_co_reschedule_self(AioContext *new_ctx);
637 
638 /**
639  * aio_co_wake:
640  * @co: the coroutine
641  *
642  * Restart a coroutine on the AioContext where it was running last, thus
643  * preventing coroutines from jumping from one context to another when they
644  * go to sleep.
645  *
646  * aio_co_wake may be executed either in coroutine or non-coroutine
647  * context.  The coroutine must not be entered by anyone else while
648  * aio_co_wake() is active.
649  */
650 void aio_co_wake(Coroutine *co);
651 
652 /**
653  * aio_co_enter:
654  * @ctx: the context to run the coroutine
655  * @co: the coroutine to run
656  *
657  * Enter a coroutine in the specified AioContext.
658  */
659 void aio_co_enter(AioContext *ctx, Coroutine *co);
660 
661 /**
662  * Return the AioContext whose event loop runs in the current thread.
663  *
664  * If called from an IOThread this will be the IOThread's AioContext.  If
665  * called from the main thread or with the "big QEMU lock" taken it
666  * will be the main loop AioContext.
667  *
668  * Note that the return value is never the main loop's iohandler_ctx and the
669  * return value is the main loop AioContext instead.
670  */
671 AioContext *qemu_get_current_aio_context(void);
672 
673 void qemu_set_current_aio_context(AioContext *ctx);
674 
675 /**
676  * aio_context_setup:
677  * @ctx: the aio context
678  *
679  * Initialize the aio context.
680  */
681 void aio_context_setup(AioContext *ctx);
682 
683 /**
684  * aio_context_destroy:
685  * @ctx: the aio context
686  *
687  * Destroy the aio context.
688  */
689 void aio_context_destroy(AioContext *ctx);
690 
691 /* Used internally, do not call outside AioContext code */
692 void aio_context_use_g_source(AioContext *ctx);
693 
694 /**
695  * aio_context_set_poll_params:
696  * @ctx: the aio context
697  * @max_ns: how long to busy poll for, in nanoseconds
698  * @grow: polling time growth factor
699  * @shrink: polling time shrink factor
700  *
701  * Poll mode can be disabled by setting poll_max_ns to 0.
702  */
703 void aio_context_set_poll_params(AioContext *ctx, int64_t max_ns,
704                                  int64_t grow, int64_t shrink,
705                                  Error **errp);
706 
707 /**
708  * aio_context_set_aio_params:
709  * @ctx: the aio context
710  * @max_batch: maximum number of requests in a batch, 0 means that the
711  *             engine will use its default
712  */
713 void aio_context_set_aio_params(AioContext *ctx, int64_t max_batch);
714 
715 /**
716  * aio_context_set_thread_pool_params:
717  * @ctx: the aio context
718  * @min: min number of threads to have readily available in the thread pool
719  * @min: max number of threads the thread pool can contain
720  */
721 void aio_context_set_thread_pool_params(AioContext *ctx, int64_t min,
722                                         int64_t max, Error **errp);
723 #endif
724