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Revision: 1.7
Committed: Sun Dec 22 15:05:32 2019 UTC (4 years, 6 months ago) by root
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Branch: MAIN
Changes since 1.6: +5 -1 lines
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# Content
1 /*
2 * libev linux io_uring fd activity backend
3 *
4 * Copyright (c) 2019 Marc Alexander Lehmann <libev@schmorp.de>
5 * All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without modifica-
8 * tion, are permitted provided that the following conditions are met:
9 *
10 * 1. Redistributions of source code must retain the above copyright notice,
11 * this list of conditions and the following disclaimer.
12 *
13 * 2. Redistributions in binary form must reproduce the above copyright
14 * notice, this list of conditions and the following disclaimer in the
15 * documentation and/or other materials provided with the distribution.
16 *
17 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
18 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MER-
19 * CHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO
20 * EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPE-
21 * CIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
22 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
23 * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
24 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTH-
25 * ERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
26 * OF THE POSSIBILITY OF SUCH DAMAGE.
27 *
28 * Alternatively, the contents of this file may be used under the terms of
29 * the GNU General Public License ("GPL") version 2 or any later version,
30 * in which case the provisions of the GPL are applicable instead of
31 * the above. If you wish to allow the use of your version of this file
32 * only under the terms of the GPL and not to allow others to use your
33 * version of this file under the BSD license, indicate your decision
34 * by deleting the provisions above and replace them with the notice
35 * and other provisions required by the GPL. If you do not delete the
36 * provisions above, a recipient may use your version of this file under
37 * either the BSD or the GPL.
38 */
39
40 /*
41 * general notes about linux io_uring:
42 *
43 * a) it's the best interface I have seen so far. on linux.
44 * b) best is not necessarily very good.
45 * c) it's better than the aio mess, doesn't suffer from the fork problems
46 * of linux aio or epoll and so on and so on. and you could do event stuff
47 * without any syscalls. what's not to like?
48 * d) ok, it's vastly more complex, but that's ok, really.
49 * e) why 3 mmaps instead of one? one would be more space-efficient,
50 * and I can't see what benefit three would have (other than being
51 * somehow resizable/relocatable, but that's apparently not possible).
52 * (FIXME: newer kernels can use 2 mmaps only, need to look into this).
53 * f) hmm, it's practiclaly undebuggable (gdb can't access the memory, and
54 * the bizarre way structure offsets are communicated makes it hard to
55 * just print the ring buffer heads, even *iff* the memory were visible
56 * in gdb. but then, that's also ok, really.
57 * g) well, you cannot specify a timeout when waiting for events. no,
58 * seriously, the interface doesn't support a timeout. never seen _that_
59 * before. sure, you can use a timerfd, but that's another syscall
60 * you could have avoided. overall, this bizarre omission smells
61 * like a ยต-optimisation by the io_uring author for his personal
62 * applications, to the detriment of everybody else who just wants
63 * an event loop. but, umm, ok, if that's all, it could be worse.
64 * (FIXME: jens mentioned timeout commands, need to investigate)
65 * h) there is a hardcoded limit of 4096 outstanding events. okay,
66 * at least there is no arbitrary low system-wide limit...
67 * (FIXME: apparently, this was increased to 32768 in later kernels(
68 * i) unlike linux aio, you *can* register more then the limit
69 * of fd events, and the kernel will "gracefully" signal an
70 * overflow, after which you could destroy and recreate the kernel
71 * state, a bit bigger, or fall back to e.g. poll. thats not
72 * totally insane, but kind of questions the point a high
73 * performance I/O framework when it doesn't really work
74 * under stress.
75 * (FIXME: iouring should no longer drop events, need to investigate)
76 * j) but, oh my! is has exactly the same bugs as the linux aio backend,
77 * where some undocumented poll combinations just fail.
78 * so we need epoll AGAIN as a fallback. AGAIN! epoll!! and of course,
79 * this is completely undocumented, have I mantioned this already?
80 * k) overall, the *API* itself is, I dare to say, not a total trainwreck.
81 * the big isuess with it are the bugs requiring epoll, which might
82 * or might not get fixed (do I hold my breath?).
83 */
84
85 #include <sys/timerfd.h>
86 #include <sys/mman.h>
87 #include <poll.h>
88
89 #define IOURING_INIT_ENTRIES 32
90
91 /*****************************************************************************/
92 /* syscall wrapdadoop - this section has the raw api/abi definitions */
93
94 #include <linux/fs.h>
95 #include <linux/types.h>
96
97 /* mostly directly taken from the kernel or documentation */
98
99 struct io_uring_sqe
100 {
101 __u8 opcode;
102 __u8 flags;
103 __u16 ioprio;
104 __s32 fd;
105 __u64 off;
106 __u64 addr;
107 __u32 len;
108 union {
109 __kernel_rwf_t rw_flags;
110 __u32 fsync_flags;
111 __u16 poll_events;
112 __u32 sync_range_flags;
113 __u32 msg_flags;
114 };
115 __u64 user_data;
116 union {
117 __u16 buf_index;
118 __u64 __pad2[3];
119 };
120 };
121
122 struct io_uring_cqe
123 {
124 __u64 user_data;
125 __s32 res;
126 __u32 flags;
127 };
128
129 struct io_sqring_offsets
130 {
131 __u32 head;
132 __u32 tail;
133 __u32 ring_mask;
134 __u32 ring_entries;
135 __u32 flags;
136 __u32 dropped;
137 __u32 array;
138 __u32 resv1;
139 __u64 resv2;
140 };
141
142 struct io_cqring_offsets
143 {
144 __u32 head;
145 __u32 tail;
146 __u32 ring_mask;
147 __u32 ring_entries;
148 __u32 overflow;
149 __u32 cqes;
150 __u64 resv[2];
151 };
152
153 struct io_uring_params
154 {
155 __u32 sq_entries;
156 __u32 cq_entries;
157 __u32 flags;
158 __u32 sq_thread_cpu;
159 __u32 sq_thread_idle;
160 __u32 resv[5];
161 struct io_sqring_offsets sq_off;
162 struct io_cqring_offsets cq_off;
163 };
164
165 #define IORING_OP_POLL_ADD 6
166 #define IORING_OP_POLL_REMOVE 7
167
168 #define IORING_ENTER_GETEVENTS 0x01
169
170 #define IORING_OFF_SQ_RING 0x00000000ULL
171 #define IORING_OFF_CQ_RING 0x08000000ULL
172 #define IORING_OFF_SQES 0x10000000ULL
173
174 inline_size
175 int
176 evsys_io_uring_setup (unsigned entries, struct io_uring_params *params)
177 {
178 return ev_syscall2 (SYS_io_uring_setup, entries, params);
179 }
180
181 inline_size
182 int
183 evsys_io_uring_enter (int fd, unsigned to_submit, unsigned min_complete, unsigned flags, const sigset_t *sig, size_t sigsz)
184 {
185 return ev_syscall6 (SYS_io_uring_enter, fd, to_submit, min_complete, flags, sig, sigsz);
186 }
187
188 /*****************************************************************************/
189 /* actual backed implementation */
190
191 /* we hope that volatile will make the compiler access this variables only once */
192 #define EV_SQ_VAR(name) *(volatile unsigned *)((char *)iouring_sq_ring + iouring_sq_ ## name)
193 #define EV_CQ_VAR(name) *(volatile unsigned *)((char *)iouring_cq_ring + iouring_cq_ ## name)
194
195 /* the index array */
196 #define EV_SQ_ARRAY ((unsigned *)((char *)iouring_sq_ring + iouring_sq_array))
197
198 /* the submit/completion queue entries */
199 #define EV_SQES ((struct io_uring_sqe *) iouring_sqes)
200 #define EV_CQES ((struct io_uring_cqe *)((char *)iouring_cq_ring + iouring_cq_cqes))
201
202 static
203 struct io_uring_sqe *
204 iouring_sqe_get (EV_P)
205 {
206 unsigned tail = EV_SQ_VAR (tail);
207
208 if (tail + 1 - EV_SQ_VAR (head) > EV_SQ_VAR (ring_entries))
209 {
210 /* queue full, flush */
211 evsys_io_uring_enter (iouring_fd, iouring_to_submit, 0, 0, 0, 0);
212 iouring_to_submit = 0;
213 }
214
215 assert (("libev: io_uring queue full after flush", tail + 1 - EV_SQ_VAR (head) <= EV_SQ_VAR (ring_entries)));
216
217 return EV_SQES + (tail & EV_SQ_VAR (ring_mask));
218 }
219
220 inline_size
221 struct io_uring_sqe *
222 iouring_sqe_submit (EV_P_ struct io_uring_sqe *sqe)
223 {
224 unsigned idx = sqe - EV_SQES;
225
226 EV_SQ_ARRAY [idx] = idx;
227 ECB_MEMORY_FENCE_RELEASE;
228 ++EV_SQ_VAR (tail);
229 /*ECB_MEMORY_FENCE_RELEASE; /* for the time being we assume this is not needed */
230 ++iouring_to_submit;
231 }
232
233 /*****************************************************************************/
234
235 /* when the timerfd expires we simply note the fact,
236 * as the purpose of the timerfd is to wake us up, nothing else.
237 * the next iteration should re-set it.
238 */
239 static void
240 iouring_tfd_cb (EV_P_ struct ev_io *w, int revents)
241 {
242 iouring_tfd_to = EV_TSTAMP_HUGE;
243 }
244
245 static void
246 iouring_epoll_cb (EV_P_ struct ev_io *w, int revents)
247 {
248 epoll_poll (EV_A_ 0);
249 }
250
251 /* called for full and partial cleanup */
252 ecb_cold
253 static int
254 iouring_internal_destroy (EV_P)
255 {
256 close (iouring_tfd);
257 close (iouring_fd);
258
259 if (iouring_sq_ring != MAP_FAILED) munmap (iouring_sq_ring, iouring_sq_ring_size);
260 if (iouring_cq_ring != MAP_FAILED) munmap (iouring_cq_ring, iouring_cq_ring_size);
261 if (iouring_sqes != MAP_FAILED) munmap (iouring_sqes , iouring_sqes_size );
262
263 if (ev_is_active (&iouring_epoll_w)) ev_ref (EV_A); ev_io_stop (EV_A_ &iouring_epoll_w);
264 if (ev_is_active (&iouring_tfd_w )) ev_ref (EV_A); ev_io_stop (EV_A_ &iouring_tfd_w );
265 }
266
267 ecb_cold
268 static int
269 iouring_internal_init (EV_P)
270 {
271 struct io_uring_params params = { 0 };
272
273 iouring_to_submit = 0;
274
275 iouring_tfd = -1;
276 iouring_sq_ring = MAP_FAILED;
277 iouring_cq_ring = MAP_FAILED;
278 iouring_sqes = MAP_FAILED;
279
280 for (;;)
281 {
282 iouring_fd = evsys_io_uring_setup (iouring_entries, &params);
283
284 if (iouring_fd >= 0)
285 break; /* yippie */
286
287 if (errno != EINVAL)
288 return -1; /* we failed */
289
290 /* EINVAL: lots of possible reasons, but maybe
291 * it is because we hit the unqueryable hardcoded size limit
292 */
293
294 /* we hit the limit already, give up */
295 if (iouring_max_entries)
296 return -1;
297
298 /* first time we hit EINVAL? assume we hit the limit, so go back and retry */
299 iouring_entries >>= 1;
300 iouring_max_entries = iouring_entries;
301 }
302
303 iouring_sq_ring_size = params.sq_off.array + params.sq_entries * sizeof (unsigned);
304 iouring_cq_ring_size = params.cq_off.cqes + params.cq_entries * sizeof (struct io_uring_cqe);
305 iouring_sqes_size = params.sq_entries * sizeof (struct io_uring_sqe);
306
307 iouring_sq_ring = mmap (0, iouring_sq_ring_size, PROT_READ | PROT_WRITE,
308 MAP_SHARED | MAP_POPULATE, iouring_fd, IORING_OFF_SQ_RING);
309 iouring_cq_ring = mmap (0, iouring_cq_ring_size, PROT_READ | PROT_WRITE,
310 MAP_SHARED | MAP_POPULATE, iouring_fd, IORING_OFF_CQ_RING);
311 iouring_sqes = mmap (0, iouring_sqes_size, PROT_READ | PROT_WRITE,
312 MAP_SHARED | MAP_POPULATE, iouring_fd, IORING_OFF_SQES);
313
314 if (iouring_sq_ring == MAP_FAILED || iouring_cq_ring == MAP_FAILED || iouring_sqes == MAP_FAILED)
315 return -1;
316
317 iouring_sq_head = params.sq_off.head;
318 iouring_sq_tail = params.sq_off.tail;
319 iouring_sq_ring_mask = params.sq_off.ring_mask;
320 iouring_sq_ring_entries = params.sq_off.ring_entries;
321 iouring_sq_flags = params.sq_off.flags;
322 iouring_sq_dropped = params.sq_off.dropped;
323 iouring_sq_array = params.sq_off.array;
324
325 iouring_cq_head = params.cq_off.head;
326 iouring_cq_tail = params.cq_off.tail;
327 iouring_cq_ring_mask = params.cq_off.ring_mask;
328 iouring_cq_ring_entries = params.cq_off.ring_entries;
329 iouring_cq_overflow = params.cq_off.overflow;
330 iouring_cq_cqes = params.cq_off.cqes;
331
332 iouring_tfd = timerfd_create (CLOCK_MONOTONIC, TFD_CLOEXEC);
333
334 if (iouring_tfd < 0)
335 return iouring_tfd;
336
337 iouring_tfd_to = EV_TSTAMP_HUGE;
338
339 return 0;
340 }
341
342 ecb_cold
343 static void
344 iouring_fork (EV_P)
345 {
346 iouring_internal_destroy (EV_A);
347
348 while (iouring_internal_init (EV_A) < 0)
349 ev_syserr ("(libev) io_uring_setup");
350
351 /* forking epoll should also effectively unregister all fds from the backend */
352 epoll_fork (EV_A);
353 /* epoll_fork already did this. hopefully */
354 /*fd_rearm_all (EV_A);*/
355
356 ev_io_stop (EV_A_ &iouring_epoll_w);
357 ev_io_set (EV_A_ &iouring_epoll_w, backend_fd, EV_READ);
358 ev_io_start (EV_A_ &iouring_epoll_w);
359
360 ev_io_stop (EV_A_ &iouring_tfd_w);
361 ev_io_set (EV_A_ &iouring_tfd_w, iouring_tfd, EV_READ);
362 ev_io_start (EV_A_ &iouring_tfd_w);
363 }
364
365 /*****************************************************************************/
366
367 static void
368 iouring_modify (EV_P_ int fd, int oev, int nev)
369 {
370 if (ecb_expect_false (anfds [fd].eflags))
371 {
372 /* we handed this fd over to epoll, so undo this first */
373 /* we do it manually because the optimisations on epoll_modify won't do us any good */
374 epoll_ctl (iouring_fd, EPOLL_CTL_DEL, fd, 0);
375 anfds [fd].eflags = 0;
376 oev = 0;
377 }
378
379 if (oev)
380 {
381 /* we assume the sqe's are all "properly" initialised */
382 struct io_uring_sqe *sqe = iouring_sqe_get (EV_A);
383 sqe->opcode = IORING_OP_POLL_REMOVE;
384 sqe->fd = fd;
385 sqe->user_data = -1;
386 iouring_sqe_submit (EV_A_ sqe);
387
388 /* increment generation counter to avoid handling old events */
389 ++anfds [fd].egen;
390 }
391
392 if (nev)
393 {
394 struct io_uring_sqe *sqe = iouring_sqe_get (EV_A);
395 sqe->opcode = IORING_OP_POLL_ADD;
396 sqe->fd = fd;
397 sqe->user_data = (uint32_t)fd | ((__u64)(uint32_t)anfds [fd].egen << 32);
398 sqe->poll_events =
399 (nev & EV_READ ? POLLIN : 0)
400 | (nev & EV_WRITE ? POLLOUT : 0);
401 iouring_sqe_submit (EV_A_ sqe);
402 }
403 }
404
405 inline_size
406 void
407 iouring_tfd_update (EV_P_ ev_tstamp timeout)
408 {
409 ev_tstamp tfd_to = mn_now + timeout;
410
411 /* we assume there will be many iterations per timer change, so
412 * we only re-set the timerfd when we have to because its expiry
413 * is too late.
414 */
415 if (ecb_expect_false (tfd_to < iouring_tfd_to))
416 {
417 struct itimerspec its;
418
419 iouring_tfd_to = tfd_to;
420 EV_TS_SET (its.it_interval, 0.);
421 EV_TS_SET (its.it_value, tfd_to);
422
423 if (timerfd_settime (iouring_tfd, TFD_TIMER_ABSTIME, &its, 0) < 0)
424 assert (("libev: iouring timerfd_settime failed", 0));
425 }
426 }
427
428 inline_size
429 void
430 iouring_process_cqe (EV_P_ struct io_uring_cqe *cqe)
431 {
432 int fd = cqe->user_data & 0xffffffffU;
433 uint32_t gen = cqe->user_data >> 32;
434 int res = cqe->res;
435
436 /* ignore fd removal events, if there are any. TODO: verify */
437 if (cqe->user_data == (__u64)-1)
438 abort ();//D
439
440 assert (("libev: io_uring fd must be in-bounds", fd >= 0 && fd < anfdmax));
441
442 /* documentation lies, of course. the result value is NOT like
443 * normal syscalls, but like linux raw syscalls, i.e. negative
444 * error numbers. fortunate, as otherwise there would be no way
445 * to get error codes at all. still, why not document this?
446 */
447
448 /* ignore event if generation doesn't match */
449 /* this should actually be very rare */
450 if (ecb_expect_false (gen != (uint32_t)anfds [fd].egen))
451 return;
452
453 if (ecb_expect_false (res < 0))
454 {
455 if (res == -EINVAL)
456 {
457 /* we assume this error code means the fd/poll combination is buggy
458 * and fall back to epoll.
459 * this error code might also indicate a bug, but the kernel doesn't
460 * distinguish between those two conditions, so... sigh...
461 */
462
463 epoll_modify (EV_A_ fd, 0, anfds [fd].events);
464 }
465 else if (res == -EBADF)
466 {
467 assert (("libev: event loop rejected bad fd", res != -EBADF));
468 fd_kill (EV_A_ fd);
469 }
470 else
471 {
472 errno = -res;
473 ev_syserr ("(libev) IORING_OP_POLL_ADD");
474 }
475
476 return;
477 }
478
479 /* feed events, we do not expect or handle POLLNVAL */
480 fd_event (
481 EV_A_
482 fd,
483 (res & (POLLOUT | POLLERR | POLLHUP) ? EV_WRITE : 0)
484 | (res & (POLLIN | POLLERR | POLLHUP) ? EV_READ : 0)
485 );
486
487 /* io_uring is oneshot, so we need to re-arm the fd next iteration */
488 /* this also means we usually have to do at least one syscall per iteration */
489 anfds [fd].events = 0;
490 fd_change (EV_A_ fd, EV_ANFD_REIFY);
491 }
492
493 /* called when the event queue overflows */
494 ecb_cold
495 static void
496 iouring_overflow (EV_P)
497 {
498 /* we have two options, resize the queue (by tearing down
499 * everything and recreating it, or living with it
500 * and polling.
501 * we implement this by resizing tghe queue, and, if that fails,
502 * we just recreate the state on every failure, which
503 * kind of is a very inefficient poll.
504 * one danger is, due to the bios toward lower fds,
505 * we will only really get events for those, so
506 * maybe we need a poll() fallback, after all.
507 */
508 /*EV_CQ_VAR (overflow) = 0;*/ /* need to do this if we keep the state and poll manually */
509
510 fd_rearm_all (EV_A);
511
512 /* we double the size until we hit the hard-to-probe maximum */
513 if (!iouring_max_entries)
514 {
515 iouring_entries <<= 1;
516 iouring_fork (EV_A);
517 }
518 else
519 {
520 /* we hit the kernel limit, we should fall back to something else.
521 * we can either poll() a few times and hope for the best,
522 * poll always, or switch to epoll.
523 * since we use epoll anyways, go epoll.
524 */
525
526 iouring_internal_destroy (EV_A);
527
528 /* this should make it so that on return, we don'T call any uring functions */
529 iouring_to_submit = 0;
530
531 for (;;)
532 {
533 backend = epoll_init (EV_A_ 0);
534
535 if (backend)
536 break;
537
538 ev_syserr ("(libev) iouring switch to epoll");
539 }
540 }
541 }
542
543 /* handle any events in the completion queue, return true if there were any */
544 static int
545 iouring_handle_cq (EV_P)
546 {
547 unsigned head, tail, mask;
548
549 head = EV_CQ_VAR (head);
550 ECB_MEMORY_FENCE_ACQUIRE;
551 tail = EV_CQ_VAR (tail);
552
553 if (head == tail)
554 return 0;
555
556 /* it can only overflow if we have events, yes, yes? */
557 if (ecb_expect_false (EV_CQ_VAR (overflow)))
558 {
559 iouring_overflow (EV_A);
560 return 1;
561 }
562
563 mask = EV_CQ_VAR (ring_mask);
564
565 do
566 iouring_process_cqe (EV_A_ &EV_CQES [head++ & mask]);
567 while (head != tail);
568
569 EV_CQ_VAR (head) = head;
570 ECB_MEMORY_FENCE_RELEASE;
571
572 return 1;
573 }
574
575 static void
576 iouring_poll (EV_P_ ev_tstamp timeout)
577 {
578 /* if we have events, no need for extra syscalls, but we might have to queue events */
579 if (iouring_handle_cq (EV_A))
580 timeout = EV_TS_CONST (0.);
581 else
582 /* no events, so maybe wait for some */
583 iouring_tfd_update (EV_A_ timeout);
584
585 /* only enter the kernel if we have something to submit, or we need to wait */
586 if (timeout || iouring_to_submit)
587 {
588 int res;
589
590 EV_RELEASE_CB;
591
592 res = evsys_io_uring_enter (iouring_fd, iouring_to_submit, 1,
593 timeout > EV_TS_CONST (0.) ? IORING_ENTER_GETEVENTS : 0, 0, 0);
594 iouring_to_submit = 0;
595
596 EV_ACQUIRE_CB;
597
598 if (ecb_expect_false (res < 0))
599 if (errno == EINTR)
600 /* ignore */;
601 else
602 ev_syserr ("(libev) iouring setup");
603 else
604 iouring_handle_cq (EV_A);
605 }
606 }
607
608 inline_size
609 int
610 iouring_init (EV_P_ int flags)
611 {
612 if (!epoll_init (EV_A_ 0))
613 return 0;
614
615 iouring_entries = IOURING_INIT_ENTRIES;
616 iouring_max_entries = 0;
617
618 if (iouring_internal_init (EV_A) < 0)
619 {
620 iouring_internal_destroy (EV_A);
621 return 0;
622 }
623
624 ev_io_init (&iouring_epoll_w, iouring_epoll_cb, backend_fd, EV_READ);
625 ev_set_priority (&iouring_epoll_w, EV_MAXPRI);
626
627 ev_io_init (&iouring_tfd_w, iouring_tfd_cb, iouring_tfd, EV_READ);
628 ev_set_priority (&iouring_tfd_w, EV_MAXPRI);
629
630 ev_io_start (EV_A_ &iouring_epoll_w);
631 ev_unref (EV_A); /* watcher should not keep loop alive */
632
633 ev_io_start (EV_A_ &iouring_tfd_w);
634 ev_unref (EV_A); /* watcher should not keep loop alive */
635
636 backend_modify = iouring_modify;
637 backend_poll = iouring_poll;
638
639 return EVBACKEND_IOURING;
640 }
641
642 inline_size
643 void
644 iouring_destroy (EV_P)
645 {
646 iouring_internal_destroy (EV_A);
647 epoll_destroy (EV_A);
648 }
649