ViewVC Help
View File | Revision Log | Show Annotations | Download File
/cvs/libev/ev_iouring.c
Revision: 1.14
Committed: Sat Dec 28 05:20:17 2019 UTC (4 years, 6 months ago) by root
Content type: text/plain
Branch: MAIN
Changes since 1.13: +41 -14 lines
Log Message:
*** empty log message ***

File Contents

# 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 /* TODO: use internal TIMEOUT */
86 /* TODO: take advantage of single mmap, NODROP etc. */
87 /* TODO: resize cq/sq size independently */
88
89 #include <sys/timerfd.h>
90 #include <sys/mman.h>
91 #include <poll.h>
92 #include <stdint.h>
93
94 #define IOURING_INIT_ENTRIES 32
95
96 /*****************************************************************************/
97 /* syscall wrapdadoop - this section has the raw api/abi definitions */
98
99 #include <linux/fs.h>
100 #include <linux/types.h>
101
102 /* mostly directly taken from the kernel or documentation */
103
104 struct io_uring_sqe
105 {
106 __u8 opcode;
107 __u8 flags;
108 __u16 ioprio;
109 __s32 fd;
110 union {
111 __u64 off;
112 __u64 addr2;
113 };
114 __u64 addr;
115 __u32 len;
116 union {
117 __kernel_rwf_t rw_flags;
118 __u32 fsync_flags;
119 __u16 poll_events;
120 __u32 sync_range_flags;
121 __u32 msg_flags;
122 __u32 timeout_flags;
123 __u32 accept_flags;
124 __u32 cancel_flags;
125 __u32 open_flags;
126 __u32 statx_flags;
127 };
128 __u64 user_data;
129 union {
130 __u16 buf_index;
131 __u64 __pad2[3];
132 };
133 };
134
135 struct io_uring_cqe
136 {
137 __u64 user_data;
138 __s32 res;
139 __u32 flags;
140 };
141
142 struct io_sqring_offsets
143 {
144 __u32 head;
145 __u32 tail;
146 __u32 ring_mask;
147 __u32 ring_entries;
148 __u32 flags;
149 __u32 dropped;
150 __u32 array;
151 __u32 resv1;
152 __u64 resv2;
153 };
154
155 struct io_cqring_offsets
156 {
157 __u32 head;
158 __u32 tail;
159 __u32 ring_mask;
160 __u32 ring_entries;
161 __u32 overflow;
162 __u32 cqes;
163 __u64 resv[2];
164 };
165
166 struct io_uring_params
167 {
168 __u32 sq_entries;
169 __u32 cq_entries;
170 __u32 flags;
171 __u32 sq_thread_cpu;
172 __u32 sq_thread_idle;
173 __u32 features;
174 __u32 resv[4];
175 struct io_sqring_offsets sq_off;
176 struct io_cqring_offsets cq_off;
177 };
178
179 #define IORING_SETUP_CQSIZE 0x00000008
180
181 #define IORING_OP_POLL_ADD 6
182 #define IORING_OP_POLL_REMOVE 7
183 #define IORING_OP_TIMEOUT 11
184 #define IORING_OP_TIMEOUT_REMOVE 12
185
186 /* relative or absolute, reference clock is CLOCK_MONOTONIC */
187 struct iouring_kernel_timespec
188 {
189 int64_t tv_sec;
190 long long tv_nsec;
191 };
192
193 #define IORING_TIMEOUT_ABS 0x00000001
194
195 #define IORING_ENTER_GETEVENTS 0x01
196
197 #define IORING_OFF_SQ_RING 0x00000000ULL
198 #define IORING_OFF_CQ_RING 0x08000000ULL
199 #define IORING_OFF_SQES 0x10000000ULL
200
201 #define IORING_FEAT_SINGLE_MMAP 0x00000001
202 #define IORING_FEAT_NODROP 0x00000002
203 #define IORING_FEAT_SUBMIT_STABLE 0x00000004
204
205 inline_size
206 int
207 evsys_io_uring_setup (unsigned entries, struct io_uring_params *params)
208 {
209 return ev_syscall2 (SYS_io_uring_setup, entries, params);
210 }
211
212 inline_size
213 int
214 evsys_io_uring_enter (int fd, unsigned to_submit, unsigned min_complete, unsigned flags, const sigset_t *sig, size_t sigsz)
215 {
216 return ev_syscall6 (SYS_io_uring_enter, fd, to_submit, min_complete, flags, sig, sigsz);
217 }
218
219 /*****************************************************************************/
220 /* actual backed implementation */
221
222 /* we hope that volatile will make the compiler access this variables only once */
223 #define EV_SQ_VAR(name) *(volatile unsigned *)((char *)iouring_sq_ring + iouring_sq_ ## name)
224 #define EV_CQ_VAR(name) *(volatile unsigned *)((char *)iouring_cq_ring + iouring_cq_ ## name)
225
226 /* the index array */
227 #define EV_SQ_ARRAY ((unsigned *)((char *)iouring_sq_ring + iouring_sq_array))
228
229 /* the submit/completion queue entries */
230 #define EV_SQES ((struct io_uring_sqe *) iouring_sqes)
231 #define EV_CQES ((struct io_uring_cqe *)((char *)iouring_cq_ring + iouring_cq_cqes))
232
233 /* TODO: this is not enough, we might have to reap events */
234 /* TODO: but we can't, as that will re-arm events, causing */
235 /* TODO: an endless loop in fd_reify */
236 static int
237 iouring_enter (EV_P_ ev_tstamp timeout)
238 {
239 int res;
240
241 EV_RELEASE_CB;
242
243 res = evsys_io_uring_enter (iouring_fd, iouring_to_submit, 1,
244 timeout > EV_TS_CONST (0.) ? IORING_ENTER_GETEVENTS : 0, 0, 0);
245
246 assert (("libev: io_uring_enter did not consume all sqes", (res < 0 || res == iouring_to_submit)));
247
248 iouring_to_submit = 0;
249
250 EV_ACQUIRE_CB;
251
252 return res;
253 }
254
255 static
256 struct io_uring_sqe *
257 iouring_sqe_get (EV_P)
258 {
259 unsigned tail = EV_SQ_VAR (tail);
260
261 while (ecb_expect_false (tail + 1 - EV_SQ_VAR (head) > EV_SQ_VAR (ring_entries)))
262 {
263 /* queue full, need to flush */
264
265 int res = iouring_enter (EV_A_ EV_TS_CONST (0.));
266
267 /* io_uring_enter might fail with EBUSY and won't submit anything */
268 /* unfortunately, we can't handle this at the moment */
269
270 if (res < 0 && errno == EBUSY)
271 //TODO
272 ev_syserr ("(libev) io_uring_enter could not clear sq");
273 else
274 break;
275
276 /* iouring_poll should have done ECB_MEMORY_FENCE_ACQUIRE */
277 }
278
279 /*assert (("libev: io_uring queue full after flush", tail + 1 - EV_SQ_VAR (head) <= EV_SQ_VAR (ring_entries)));*/
280
281 return EV_SQES + (tail & EV_SQ_VAR (ring_mask));
282 }
283
284 inline_size
285 struct io_uring_sqe *
286 iouring_sqe_submit (EV_P_ struct io_uring_sqe *sqe)
287 {
288 unsigned idx = sqe - EV_SQES;
289
290 EV_SQ_ARRAY [idx] = idx;
291 ECB_MEMORY_FENCE_RELEASE;
292 ++EV_SQ_VAR (tail);
293 /*ECB_MEMORY_FENCE_RELEASE; /* for the time being we assume this is not needed */
294 ++iouring_to_submit;
295 }
296
297 /*****************************************************************************/
298
299 /* when the timerfd expires we simply note the fact,
300 * as the purpose of the timerfd is to wake us up, nothing else.
301 * the next iteration should re-set it.
302 */
303 static void
304 iouring_tfd_cb (EV_P_ struct ev_io *w, int revents)
305 {
306 iouring_tfd_to = EV_TSTAMP_HUGE;
307 }
308
309 /* called for full and partial cleanup */
310 ecb_cold
311 static int
312 iouring_internal_destroy (EV_P)
313 {
314 close (iouring_tfd);
315 close (iouring_fd);
316
317 if (iouring_sq_ring != MAP_FAILED) munmap (iouring_sq_ring, iouring_sq_ring_size);
318 if (iouring_cq_ring != MAP_FAILED) munmap (iouring_cq_ring, iouring_cq_ring_size);
319 if (iouring_sqes != MAP_FAILED) munmap (iouring_sqes , iouring_sqes_size );
320
321 if (ev_is_active (&iouring_tfd_w))
322 {
323 ev_ref (EV_A);
324 ev_io_stop (EV_A_ &iouring_tfd_w);
325 }
326 }
327
328 ecb_cold
329 static int
330 iouring_internal_init (EV_P)
331 {
332 struct io_uring_params params = { 0 };
333
334 iouring_to_submit = 0;
335
336 iouring_tfd = -1;
337 iouring_sq_ring = MAP_FAILED;
338 iouring_cq_ring = MAP_FAILED;
339 iouring_sqes = MAP_FAILED;
340
341 if (!have_monotonic) /* cannot really happen, but what if11 */
342 return -1;
343
344 for (;;)
345 {
346 iouring_fd = evsys_io_uring_setup (iouring_entries, &params);
347
348 if (iouring_fd >= 0)
349 break; /* yippie */
350
351 if (errno != EINVAL)
352 return -1; /* we failed */
353
354 #if TODO
355 if ((~params.features) & (IORING_FEAT_NODROP | IORING_FEATURE_SINGLE_MMAP))
356 return -1; /* we require the above features */
357 #endif
358
359 /* EINVAL: lots of possible reasons, but maybe
360 * it is because we hit the unqueryable hardcoded size limit
361 */
362
363 /* we hit the limit already, give up */
364 if (iouring_max_entries)
365 return -1;
366
367 /* first time we hit EINVAL? assume we hit the limit, so go back and retry */
368 iouring_entries >>= 1;
369 iouring_max_entries = iouring_entries;
370 }
371
372 iouring_sq_ring_size = params.sq_off.array + params.sq_entries * sizeof (unsigned);
373 iouring_cq_ring_size = params.cq_off.cqes + params.cq_entries * sizeof (struct io_uring_cqe);
374 iouring_sqes_size = params.sq_entries * sizeof (struct io_uring_sqe);
375
376 iouring_sq_ring = mmap (0, iouring_sq_ring_size, PROT_READ | PROT_WRITE,
377 MAP_SHARED | MAP_POPULATE, iouring_fd, IORING_OFF_SQ_RING);
378 iouring_cq_ring = mmap (0, iouring_cq_ring_size, PROT_READ | PROT_WRITE,
379 MAP_SHARED | MAP_POPULATE, iouring_fd, IORING_OFF_CQ_RING);
380 iouring_sqes = mmap (0, iouring_sqes_size, PROT_READ | PROT_WRITE,
381 MAP_SHARED | MAP_POPULATE, iouring_fd, IORING_OFF_SQES);
382
383 if (iouring_sq_ring == MAP_FAILED || iouring_cq_ring == MAP_FAILED || iouring_sqes == MAP_FAILED)
384 return -1;
385
386 iouring_sq_head = params.sq_off.head;
387 iouring_sq_tail = params.sq_off.tail;
388 iouring_sq_ring_mask = params.sq_off.ring_mask;
389 iouring_sq_ring_entries = params.sq_off.ring_entries;
390 iouring_sq_flags = params.sq_off.flags;
391 iouring_sq_dropped = params.sq_off.dropped;
392 iouring_sq_array = params.sq_off.array;
393
394 iouring_cq_head = params.cq_off.head;
395 iouring_cq_tail = params.cq_off.tail;
396 iouring_cq_ring_mask = params.cq_off.ring_mask;
397 iouring_cq_ring_entries = params.cq_off.ring_entries;
398 iouring_cq_overflow = params.cq_off.overflow;
399 iouring_cq_cqes = params.cq_off.cqes;
400
401 iouring_tfd = timerfd_create (CLOCK_MONOTONIC, TFD_CLOEXEC);
402
403 if (iouring_tfd < 0)
404 return iouring_tfd;
405
406 iouring_tfd_to = EV_TSTAMP_HUGE;
407
408 return 0;
409 }
410
411 ecb_cold
412 static void
413 iouring_fork (EV_P)
414 {
415 iouring_internal_destroy (EV_A);
416
417 while (iouring_internal_init (EV_A) < 0)
418 ev_syserr ("(libev) io_uring_setup");
419
420 fd_rearm_all (EV_A);
421
422 ev_io_stop (EV_A_ &iouring_tfd_w);
423 ev_io_set (EV_A_ &iouring_tfd_w, iouring_tfd, EV_READ);
424 ev_io_start (EV_A_ &iouring_tfd_w);
425 }
426
427 /*****************************************************************************/
428
429 static void
430 iouring_modify (EV_P_ int fd, int oev, int nev)
431 {
432 if (oev)
433 {
434 /* we assume the sqe's are all "properly" initialised */
435 struct io_uring_sqe *sqe = iouring_sqe_get (EV_A);
436 sqe->opcode = IORING_OP_POLL_REMOVE;
437 sqe->fd = fd;
438 /* Jens Axboe notified me that user_data is not what is documented, but is
439 * some kind of unique ID that has to match, otherwise the request cannot
440 * be removed. Since we don't *really* have that, we pass in the old
441 * generation counter - if that fails, too bad, it will hopefully be removed
442 * at close time and then be ignored. */
443 sqe->user_data = (uint32_t)fd | ((__u64)(uint32_t)anfds [fd].egen << 32);
444 iouring_sqe_submit (EV_A_ sqe);
445
446 /* increment generation counter to avoid handling old events */
447 ++anfds [fd].egen;
448 }
449
450 if (nev)
451 {
452 struct io_uring_sqe *sqe = iouring_sqe_get (EV_A);
453 sqe->opcode = IORING_OP_POLL_ADD;
454 sqe->fd = fd;
455 sqe->user_data = (uint32_t)fd | ((__u64)(uint32_t)anfds [fd].egen << 32);
456 sqe->poll_events =
457 (nev & EV_READ ? POLLIN : 0)
458 | (nev & EV_WRITE ? POLLOUT : 0);
459 iouring_sqe_submit (EV_A_ sqe);
460 }
461 }
462
463 inline_size
464 void
465 iouring_tfd_update (EV_P_ ev_tstamp timeout)
466 {
467 ev_tstamp tfd_to = mn_now + timeout;
468
469 /* we assume there will be many iterations per timer change, so
470 * we only re-set the timerfd when we have to because its expiry
471 * is too late.
472 */
473 if (ecb_expect_false (tfd_to < iouring_tfd_to))
474 {
475 struct itimerspec its;
476
477 iouring_tfd_to = tfd_to;
478 EV_TS_SET (its.it_interval, 0.);
479 EV_TS_SET (its.it_value, tfd_to);
480
481 if (timerfd_settime (iouring_tfd, TFD_TIMER_ABSTIME, &its, 0) < 0)
482 assert (("libev: iouring timerfd_settime failed", 0));
483 }
484 }
485
486 inline_size
487 void
488 iouring_process_cqe (EV_P_ struct io_uring_cqe *cqe)
489 {
490 int fd = cqe->user_data & 0xffffffffU;
491 uint32_t gen = cqe->user_data >> 32;
492 int res = cqe->res;
493
494 assert (("libev: io_uring fd must be in-bounds", fd >= 0 && fd < anfdmax));
495
496 /* documentation lies, of course. the result value is NOT like
497 * normal syscalls, but like linux raw syscalls, i.e. negative
498 * error numbers. fortunate, as otherwise there would be no way
499 * to get error codes at all. still, why not document this?
500 */
501
502 /* ignore event if generation doesn't match */
503 /* other than skipping removal events, */
504 /* this should actually be very rare */
505 if (ecb_expect_false (gen != (uint32_t)anfds [fd].egen))
506 return;
507
508 if (ecb_expect_false (res < 0))
509 {
510 /*TODO: EINVAL handling (was something failed with this fd)*/
511 /*TODO: EBUSY happens when?*/
512
513 if (res == -EBADF)
514 {
515 assert (("libev: event loop rejected bad fd", res != -EBADF));
516 fd_kill (EV_A_ fd);
517 }
518 else
519 {
520 errno = -res;
521 ev_syserr ("(libev) IORING_OP_POLL_ADD");
522 }
523
524 return;
525 }
526
527 /* feed events, we do not expect or handle POLLNVAL */
528 fd_event (
529 EV_A_
530 fd,
531 (res & (POLLOUT | POLLERR | POLLHUP) ? EV_WRITE : 0)
532 | (res & (POLLIN | POLLERR | POLLHUP) ? EV_READ : 0)
533 );
534
535 /* io_uring is oneshot, so we need to re-arm the fd next iteration */
536 /* this also means we usually have to do at least one syscall per iteration */
537 anfds [fd].events = 0;
538 fd_change (EV_A_ fd, EV_ANFD_REIFY);
539 }
540
541 /* called when the event queue overflows */
542 ecb_cold
543 static void
544 iouring_overflow (EV_P)
545 {
546 /* we have two options, resize the queue (by tearing down
547 * everything and recreating it, or living with it
548 * and polling.
549 * we implement this by resizing the queue, and, if that fails,
550 * we just recreate the state on every failure, which
551 * kind of is a very inefficient poll.
552 * one danger is, due to the bios toward lower fds,
553 * we will only really get events for those, so
554 * maybe we need a poll() fallback, after all.
555 */
556 /*EV_CQ_VAR (overflow) = 0;*/ /* need to do this if we keep the state and poll manually */
557
558 fd_rearm_all (EV_A);
559
560 /* we double the size until we hit the hard-to-probe maximum */
561 if (!iouring_max_entries)
562 {
563 iouring_entries <<= 1;
564 iouring_fork (EV_A);
565 }
566 else
567 {
568 /* we hit the kernel limit, we should fall back to something else.
569 * we can either poll() a few times and hope for the best,
570 * poll always, or switch to epoll.
571 * TODO: is this necessary with newer kernels?
572 */
573
574 iouring_internal_destroy (EV_A);
575
576 /* this should make it so that on return, we don't call any uring functions */
577 iouring_to_submit = 0;
578
579 for (;;)
580 {
581 backend = epoll_init (EV_A_ 0);
582
583 if (backend)
584 break;
585
586 ev_syserr ("(libev) iouring switch to epoll");
587 }
588 }
589 }
590
591 /* handle any events in the completion queue, return true if there were any */
592 static int
593 iouring_handle_cq (EV_P)
594 {
595 unsigned head, tail, mask;
596
597 head = EV_CQ_VAR (head);
598 ECB_MEMORY_FENCE_ACQUIRE;
599 tail = EV_CQ_VAR (tail);
600
601 if (head == tail)
602 return 0;
603
604 /* it can only overflow if we have events, yes, yes? */
605 if (ecb_expect_false (EV_CQ_VAR (overflow)))
606 {
607 iouring_overflow (EV_A);
608 return 1;
609 }
610
611 mask = EV_CQ_VAR (ring_mask);
612
613 do
614 iouring_process_cqe (EV_A_ &EV_CQES [head++ & mask]);
615 while (head != tail);
616
617 EV_CQ_VAR (head) = head;
618 ECB_MEMORY_FENCE_RELEASE;
619
620 return 1;
621 }
622
623 static void
624 iouring_poll (EV_P_ ev_tstamp timeout)
625 {
626 /* if we have events, no need for extra syscalls, but we might have to queue events */
627 if (iouring_handle_cq (EV_A))
628 timeout = EV_TS_CONST (0.);
629 else
630 /* no events, so maybe wait for some */
631 iouring_tfd_update (EV_A_ timeout);
632
633 /* only enter the kernel if we have something to submit, or we need to wait */
634 if (timeout || iouring_to_submit)
635 {
636 int res = iouring_enter (EV_A_ timeout);
637
638 if (ecb_expect_false (res < 0))
639 if (errno == EINTR)
640 /* ignore */;
641 else if (errno == EBUSY)
642 /* cq full, cannot submit - should be rare because we flush the cq first, so simply ignore */;
643 else
644 ev_syserr ("(libev) iouring setup");
645 else
646 iouring_handle_cq (EV_A);
647 }
648 }
649
650 inline_size
651 int
652 iouring_init (EV_P_ int flags)
653 {
654 iouring_entries = IOURING_INIT_ENTRIES;
655 iouring_max_entries = 0;
656
657 if (iouring_internal_init (EV_A) < 0)
658 {
659 iouring_internal_destroy (EV_A);
660 return 0;
661 }
662
663 ev_io_init (&iouring_tfd_w, iouring_tfd_cb, iouring_tfd, EV_READ);
664 ev_set_priority (&iouring_tfd_w, EV_MINPRI);
665 ev_io_start (EV_A_ &iouring_tfd_w);
666 ev_unref (EV_A); /* watcher should not keep loop alive */
667
668 backend_modify = iouring_modify;
669 backend_poll = iouring_poll;
670
671 return EVBACKEND_IOURING;
672 }
673
674 inline_size
675 void
676 iouring_destroy (EV_P)
677 {
678 iouring_internal_destroy (EV_A);
679 }
680