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Revision: 1.18
Committed: Sat Dec 28 07:57:48 2019 UTC (4 years, 6 months ago) by root
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Branch: MAIN
Changes since 1.17: +17 -21 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 two mmaps instead of one? one would be more space-efficient,
50 * and I can't see what benefit two would have (other than being
51 * somehow resizable/relocatable, but that's apparently not possible).
52 * f) hmm, it's practically undebuggable (gdb can't access the memory, and
53 * the bizarre way structure offsets are communicated makes it hard to
54 * just print the ring buffer heads, even *iff* the memory were visible
55 * in gdb. but then, that's also ok, really.
56 * g) well, you cannot specify a timeout when waiting for events. no,
57 * seriously, the interface doesn't support a timeout. never seen _that_
58 * before. sure, you can use a timerfd, but that's another syscall
59 * you could have avoided. overall, this bizarre omission smells
60 * like a ยต-optimisation by the io_uring author for his personal
61 * applications, to the detriment of everybody else who just wants
62 * an event loop. but, umm, ok, if that's all, it could be worse.
63 * (from what I gather form Jens Axboe, it simply didn't occur to him,
64 * and he made good on it by adding an unlimited nuber of timeouts
65 * later :).
66 * h) initially there was a hardcoded limit of 4096 outstanding events.
67 * later versions not onlyx bump this to 32k, but also can handle
68 * an unlimited amount of events, so this only affects the batch size.
69 * i) unlike linux aio, you *can* register more then the limit
70 * of fd events. while early verisons of io_uring signalled an overflow
71 * and you ended up getting wet. 5.5+ does not do this anymore.
72 * j) but, oh my! it had exactly the same bugs as the linux aio backend,
73 * where some undocumented poll combinations just fail. fortunately,
74 * after finally reaching the author, he was more than willing to fix
75 * this probably in 5.6+.
76 * k) overall, the *API* itself is, I dare to say, not a total trainwreck.
77 * once the bugs ae fixed (probably in 5.6+), it will be without
78 * competition.
79 */
80
81 /* TODO: use internal TIMEOUT */
82 /* TODO: take advantage of single mmap, NODROP etc. */
83 /* TODO: resize cq/sq size independently */
84
85 #include <sys/timerfd.h>
86 #include <sys/mman.h>
87 #include <poll.h>
88 #include <stdint.h>
89
90 #define IOURING_INIT_ENTRIES 32
91
92 /*****************************************************************************/
93 /* syscall wrapdadoop - this section has the raw api/abi definitions */
94
95 #include <linux/fs.h>
96 #include <linux/types.h>
97
98 /* mostly directly taken from the kernel or documentation */
99
100 struct io_uring_sqe
101 {
102 __u8 opcode;
103 __u8 flags;
104 __u16 ioprio;
105 __s32 fd;
106 union {
107 __u64 off;
108 __u64 addr2;
109 };
110 __u64 addr;
111 __u32 len;
112 union {
113 __kernel_rwf_t rw_flags;
114 __u32 fsync_flags;
115 __u16 poll_events;
116 __u32 sync_range_flags;
117 __u32 msg_flags;
118 __u32 timeout_flags;
119 __u32 accept_flags;
120 __u32 cancel_flags;
121 __u32 open_flags;
122 __u32 statx_flags;
123 };
124 __u64 user_data;
125 union {
126 __u16 buf_index;
127 __u64 __pad2[3];
128 };
129 };
130
131 struct io_uring_cqe
132 {
133 __u64 user_data;
134 __s32 res;
135 __u32 flags;
136 };
137
138 struct io_sqring_offsets
139 {
140 __u32 head;
141 __u32 tail;
142 __u32 ring_mask;
143 __u32 ring_entries;
144 __u32 flags;
145 __u32 dropped;
146 __u32 array;
147 __u32 resv1;
148 __u64 resv2;
149 };
150
151 struct io_cqring_offsets
152 {
153 __u32 head;
154 __u32 tail;
155 __u32 ring_mask;
156 __u32 ring_entries;
157 __u32 overflow;
158 __u32 cqes;
159 __u64 resv[2];
160 };
161
162 struct io_uring_params
163 {
164 __u32 sq_entries;
165 __u32 cq_entries;
166 __u32 flags;
167 __u32 sq_thread_cpu;
168 __u32 sq_thread_idle;
169 __u32 features;
170 __u32 resv[4];
171 struct io_sqring_offsets sq_off;
172 struct io_cqring_offsets cq_off;
173 };
174
175 #define IORING_SETUP_CQSIZE 0x00000008
176
177 #define IORING_OP_POLL_ADD 6
178 #define IORING_OP_POLL_REMOVE 7
179 #define IORING_OP_TIMEOUT 11
180 #define IORING_OP_TIMEOUT_REMOVE 12
181
182 /* relative or absolute, reference clock is CLOCK_MONOTONIC */
183 struct iouring_kernel_timespec
184 {
185 int64_t tv_sec;
186 long long tv_nsec;
187 };
188
189 #define IORING_TIMEOUT_ABS 0x00000001
190
191 #define IORING_ENTER_GETEVENTS 0x01
192
193 #define IORING_OFF_SQ_RING 0x00000000ULL
194 #define IORING_OFF_CQ_RING 0x08000000ULL
195 #define IORING_OFF_SQES 0x10000000ULL
196
197 #define IORING_FEAT_SINGLE_MMAP 0x00000001
198 #define IORING_FEAT_NODROP 0x00000002
199 #define IORING_FEAT_SUBMIT_STABLE 0x00000004
200
201 inline_size
202 int
203 evsys_io_uring_setup (unsigned entries, struct io_uring_params *params)
204 {
205 return ev_syscall2 (SYS_io_uring_setup, entries, params);
206 }
207
208 inline_size
209 int
210 evsys_io_uring_enter (int fd, unsigned to_submit, unsigned min_complete, unsigned flags, const sigset_t *sig, size_t sigsz)
211 {
212 return ev_syscall6 (SYS_io_uring_enter, fd, to_submit, min_complete, flags, sig, sigsz);
213 }
214
215 /*****************************************************************************/
216 /* actual backed implementation */
217
218 /* we hope that volatile will make the compiler access this variables only once */
219 #define EV_SQ_VAR(name) *(volatile unsigned *)((char *)iouring_sq_ring + iouring_sq_ ## name)
220 #define EV_CQ_VAR(name) *(volatile unsigned *)((char *)iouring_cq_ring + iouring_cq_ ## name)
221
222 /* the index array */
223 #define EV_SQ_ARRAY ((unsigned *)((char *)iouring_sq_ring + iouring_sq_array))
224
225 /* the submit/completion queue entries */
226 #define EV_SQES ((struct io_uring_sqe *) iouring_sqes)
227 #define EV_CQES ((struct io_uring_cqe *)((char *)iouring_cq_ring + iouring_cq_cqes))
228
229 inline_speed
230 int
231 iouring_enter (EV_P_ ev_tstamp timeout)
232 {
233 int res;
234
235 EV_RELEASE_CB;
236
237 res = evsys_io_uring_enter (iouring_fd, iouring_to_submit, 1,
238 timeout > EV_TS_CONST (0.) ? IORING_ENTER_GETEVENTS : 0, 0, 0);
239
240 assert (("libev: io_uring_enter did not consume all sqes", (res < 0 || res == iouring_to_submit)));
241
242 iouring_to_submit = 0;
243
244 EV_ACQUIRE_CB;
245
246 return res;
247 }
248
249 /* TODO: can we move things around so we don't need this forward-reference? */
250 static void
251 iouring_poll (EV_P_ ev_tstamp timeout);
252
253 static
254 struct io_uring_sqe *
255 iouring_sqe_get (EV_P)
256 {
257 unsigned tail;
258
259 for (;;)
260 {
261 tail = EV_SQ_VAR (tail);
262
263 if (ecb_expect_true (tail + 1 - EV_SQ_VAR (head) <= EV_SQ_VAR (ring_entries)))
264 break; /* whats the problem, we have free sqes */
265
266 /* queue full, need to flush and possibly handle some events */
267
268 #if EV_FEATURE_CODE
269 /* first we ask the kernel nicely, most often this frees up some sqes */
270 int res = iouring_enter (EV_A_ EV_TS_CONST (0.));
271
272 ECB_MEMORY_FENCE_ACQUIRE; /* better safe than sorry */
273
274 if (res >= 0)
275 continue; /* yes, it worked, try again */
276 #endif
277
278 /* some problem, possibly EBUSY - do the full poll and let it handle any issues */
279
280 iouring_poll (EV_A_ EV_TS_CONST (0.));
281 /* iouring_poll should have done ECB_MEMORY_FENCE_ACQUIRE for us */
282 }
283
284 /*assert (("libev: io_uring queue full after flush", tail + 1 - EV_SQ_VAR (head) <= EV_SQ_VAR (ring_entries)));*/
285
286 return EV_SQES + (tail & EV_SQ_VAR (ring_mask));
287 }
288
289 inline_size
290 struct io_uring_sqe *
291 iouring_sqe_submit (EV_P_ struct io_uring_sqe *sqe)
292 {
293 unsigned idx = sqe - EV_SQES;
294
295 EV_SQ_ARRAY [idx] = idx;
296 ECB_MEMORY_FENCE_RELEASE;
297 ++EV_SQ_VAR (tail);
298 /*ECB_MEMORY_FENCE_RELEASE; /* for the time being we assume this is not needed */
299 ++iouring_to_submit;
300 }
301
302 /*****************************************************************************/
303
304 /* when the timerfd expires we simply note the fact,
305 * as the purpose of the timerfd is to wake us up, nothing else.
306 * the next iteration should re-set it.
307 */
308 static void
309 iouring_tfd_cb (EV_P_ struct ev_io *w, int revents)
310 {
311 iouring_tfd_to = EV_TSTAMP_HUGE;
312 }
313
314 /* called for full and partial cleanup */
315 ecb_cold
316 static int
317 iouring_internal_destroy (EV_P)
318 {
319 close (iouring_tfd);
320 close (iouring_fd);
321
322 if (iouring_sq_ring != MAP_FAILED) munmap (iouring_sq_ring, iouring_sq_ring_size);
323 if (iouring_cq_ring != MAP_FAILED) munmap (iouring_cq_ring, iouring_cq_ring_size);
324 if (iouring_sqes != MAP_FAILED) munmap (iouring_sqes , iouring_sqes_size );
325
326 if (ev_is_active (&iouring_tfd_w))
327 {
328 ev_ref (EV_A);
329 ev_io_stop (EV_A_ &iouring_tfd_w);
330 }
331 }
332
333 ecb_cold
334 static int
335 iouring_internal_init (EV_P)
336 {
337 struct io_uring_params params = { 0 };
338
339 iouring_to_submit = 0;
340
341 iouring_tfd = -1;
342 iouring_sq_ring = MAP_FAILED;
343 iouring_cq_ring = MAP_FAILED;
344 iouring_sqes = MAP_FAILED;
345
346 if (!have_monotonic) /* cannot really happen, but what if11 */
347 return -1;
348
349 for (;;)
350 {
351 iouring_fd = evsys_io_uring_setup (iouring_entries, &params);
352
353 if (iouring_fd >= 0)
354 break; /* yippie */
355
356 if (errno != EINVAL)
357 return -1; /* we failed */
358
359 #if TODO
360 if ((~params.features) & (IORING_FEAT_NODROP | IORING_FEATURE_SINGLE_MMAP | IORING_FEAT_SUBMIT_STABLE))
361 return -1; /* we require the above features */
362 #endif
363
364 /* EINVAL: lots of possible reasons, but maybe
365 * it is because we hit the unqueryable hardcoded size limit
366 */
367
368 /* we hit the limit already, give up */
369 if (iouring_max_entries)
370 return -1;
371
372 /* first time we hit EINVAL? assume we hit the limit, so go back and retry */
373 iouring_entries >>= 1;
374 iouring_max_entries = iouring_entries;
375 }
376
377 iouring_sq_ring_size = params.sq_off.array + params.sq_entries * sizeof (unsigned);
378 iouring_cq_ring_size = params.cq_off.cqes + params.cq_entries * sizeof (struct io_uring_cqe);
379 iouring_sqes_size = params.sq_entries * sizeof (struct io_uring_sqe);
380
381 iouring_sq_ring = mmap (0, iouring_sq_ring_size, PROT_READ | PROT_WRITE,
382 MAP_SHARED | MAP_POPULATE, iouring_fd, IORING_OFF_SQ_RING);
383 iouring_cq_ring = mmap (0, iouring_cq_ring_size, PROT_READ | PROT_WRITE,
384 MAP_SHARED | MAP_POPULATE, iouring_fd, IORING_OFF_CQ_RING);
385 iouring_sqes = mmap (0, iouring_sqes_size, PROT_READ | PROT_WRITE,
386 MAP_SHARED | MAP_POPULATE, iouring_fd, IORING_OFF_SQES);
387
388 if (iouring_sq_ring == MAP_FAILED || iouring_cq_ring == MAP_FAILED || iouring_sqes == MAP_FAILED)
389 return -1;
390
391 iouring_sq_head = params.sq_off.head;
392 iouring_sq_tail = params.sq_off.tail;
393 iouring_sq_ring_mask = params.sq_off.ring_mask;
394 iouring_sq_ring_entries = params.sq_off.ring_entries;
395 iouring_sq_flags = params.sq_off.flags;
396 iouring_sq_dropped = params.sq_off.dropped;
397 iouring_sq_array = params.sq_off.array;
398
399 iouring_cq_head = params.cq_off.head;
400 iouring_cq_tail = params.cq_off.tail;
401 iouring_cq_ring_mask = params.cq_off.ring_mask;
402 iouring_cq_ring_entries = params.cq_off.ring_entries;
403 iouring_cq_overflow = params.cq_off.overflow;
404 iouring_cq_cqes = params.cq_off.cqes;
405
406 iouring_tfd = timerfd_create (CLOCK_MONOTONIC, TFD_CLOEXEC);
407
408 if (iouring_tfd < 0)
409 return iouring_tfd;
410
411 iouring_tfd_to = EV_TSTAMP_HUGE;
412
413 return 0;
414 }
415
416 ecb_cold
417 static void
418 iouring_fork (EV_P)
419 {
420 iouring_internal_destroy (EV_A);
421
422 while (iouring_internal_init (EV_A) < 0)
423 ev_syserr ("(libev) io_uring_setup");
424
425 fd_rearm_all (EV_A);
426
427 ev_io_stop (EV_A_ &iouring_tfd_w);
428 ev_io_set (EV_A_ &iouring_tfd_w, iouring_tfd, EV_READ);
429 ev_io_start (EV_A_ &iouring_tfd_w);
430 }
431
432 /*****************************************************************************/
433
434 static void
435 iouring_modify (EV_P_ int fd, int oev, int nev)
436 {
437 if (oev)
438 {
439 /* we assume the sqe's are all "properly" initialised */
440 struct io_uring_sqe *sqe = iouring_sqe_get (EV_A);
441 sqe->opcode = IORING_OP_POLL_REMOVE;
442 sqe->fd = fd;
443 /* Jens Axboe notified me that user_data is not what is documented, but is
444 * some kind of unique ID that has to match, otherwise the request cannot
445 * be removed. Since we don't *really* have that, we pass in the old
446 * generation counter - if that fails, too bad, it will hopefully be removed
447 * at close time and then be ignored. */
448 sqe->addr = (uint32_t)fd | ((__u64)(uint32_t)anfds [fd].egen << 32);
449 sqe->user_data = (uint64_t)-1;
450 iouring_sqe_submit (EV_A_ sqe);
451
452 /* increment generation counter to avoid handling old events */
453 ++anfds [fd].egen;
454 }
455
456 if (nev)
457 {
458 struct io_uring_sqe *sqe = iouring_sqe_get (EV_A);
459 sqe->opcode = IORING_OP_POLL_ADD;
460 sqe->fd = fd;
461 sqe->user_data = (uint32_t)fd | ((__u64)(uint32_t)anfds [fd].egen << 32);
462 sqe->poll_events =
463 (nev & EV_READ ? POLLIN : 0)
464 | (nev & EV_WRITE ? POLLOUT : 0);
465 iouring_sqe_submit (EV_A_ sqe);
466 }
467 }
468
469 inline_size
470 void
471 iouring_tfd_update (EV_P_ ev_tstamp timeout)
472 {
473 ev_tstamp tfd_to = mn_now + timeout;
474
475 /* we assume there will be many iterations per timer change, so
476 * we only re-set the timerfd when we have to because its expiry
477 * is too late.
478 */
479 if (ecb_expect_false (tfd_to < iouring_tfd_to))
480 {
481 struct itimerspec its;
482
483 iouring_tfd_to = tfd_to;
484 EV_TS_SET (its.it_interval, 0.);
485 EV_TS_SET (its.it_value, tfd_to);
486
487 if (timerfd_settime (iouring_tfd, TFD_TIMER_ABSTIME, &its, 0) < 0)
488 assert (("libev: iouring timerfd_settime failed", 0));
489 }
490 }
491
492 inline_size
493 void
494 iouring_process_cqe (EV_P_ struct io_uring_cqe *cqe)
495 {
496 int fd = cqe->user_data & 0xffffffffU;
497 uint32_t gen = cqe->user_data >> 32;
498 int res = cqe->res;
499
500 /* user_data -1 is a remove that we are not atm. interested in */
501 if (cqe->user_data == (uint64_t)-1)
502 return;
503
504 assert (("libev: io_uring fd must be in-bounds", fd >= 0 && fd < anfdmax));
505
506 /* documentation lies, of course. the result value is NOT like
507 * normal syscalls, but like linux raw syscalls, i.e. negative
508 * error numbers. fortunate, as otherwise there would be no way
509 * to get error codes at all. still, why not document this?
510 */
511
512 /* ignore event if generation doesn't match */
513 /* other than skipping removal events, */
514 /* this should actually be very rare */
515 if (ecb_expect_false (gen != (uint32_t)anfds [fd].egen))
516 return;
517
518 if (ecb_expect_false (res < 0))
519 {
520 /*TODO: EINVAL handling (was something failed with this fd)*/
521 /*TODO: EBUSY happens when?*/
522
523 if (res == -EBADF)
524 {
525 assert (("libev: event loop rejected bad fd", res != -EBADF));
526 fd_kill (EV_A_ fd);
527 }
528 else
529 {
530 errno = -res;
531 ev_syserr ("(libev) IORING_OP_POLL_ADD");
532 }
533
534 return;
535 }
536
537 /* feed events, we do not expect or handle POLLNVAL */
538 fd_event (
539 EV_A_
540 fd,
541 (res & (POLLOUT | POLLERR | POLLHUP) ? EV_WRITE : 0)
542 | (res & (POLLIN | POLLERR | POLLHUP) ? EV_READ : 0)
543 );
544
545 /* io_uring is oneshot, so we need to re-arm the fd next iteration */
546 /* this also means we usually have to do at least one syscall per iteration */
547 anfds [fd].events = 0;
548 fd_change (EV_A_ fd, EV_ANFD_REIFY);
549 }
550
551 /* called when the event queue overflows */
552 ecb_cold
553 static void
554 iouring_overflow (EV_P)
555 {
556 /* we have two options, resize the queue (by tearing down
557 * everything and recreating it, or living with it
558 * and polling.
559 * we implement this by resizing the queue, and, if that fails,
560 * we just recreate the state on every failure, which
561 * kind of is a very inefficient poll.
562 * one danger is, due to the bios toward lower fds,
563 * we will only really get events for those, so
564 * maybe we need a poll() fallback, after all.
565 */
566 /*EV_CQ_VAR (overflow) = 0;*/ /* need to do this if we keep the state and poll manually */
567
568 fd_rearm_all (EV_A);
569
570 /* we double the size until we hit the hard-to-probe maximum */
571 if (!iouring_max_entries)
572 {
573 iouring_entries <<= 1;
574 iouring_fork (EV_A);
575 }
576 else
577 {
578 /* we hit the kernel limit, we should fall back to something else.
579 * we can either poll() a few times and hope for the best,
580 * poll always, or switch to epoll.
581 * TODO: is this necessary with newer kernels?
582 */
583
584 iouring_internal_destroy (EV_A);
585
586 /* this should make it so that on return, we don't call any uring functions */
587 iouring_to_submit = 0;
588
589 for (;;)
590 {
591 backend = epoll_init (EV_A_ 0);
592
593 if (backend)
594 break;
595
596 ev_syserr ("(libev) iouring switch to epoll");
597 }
598 }
599 }
600
601 /* handle any events in the completion queue, return true if there were any */
602 static int
603 iouring_handle_cq (EV_P)
604 {
605 unsigned head, tail, mask;
606
607 head = EV_CQ_VAR (head);
608 ECB_MEMORY_FENCE_ACQUIRE;
609 tail = EV_CQ_VAR (tail);
610
611 if (head == tail)
612 return 0;
613
614 /* it can only overflow if we have events, yes, yes? */
615 if (ecb_expect_false (EV_CQ_VAR (overflow)))
616 {
617 iouring_overflow (EV_A);
618 return 1;
619 }
620
621 mask = EV_CQ_VAR (ring_mask);
622
623 do
624 iouring_process_cqe (EV_A_ &EV_CQES [head++ & mask]);
625 while (head != tail);
626
627 EV_CQ_VAR (head) = head;
628 ECB_MEMORY_FENCE_RELEASE;
629
630 return 1;
631 }
632
633 static void
634 iouring_poll (EV_P_ ev_tstamp timeout)
635 {
636 /* if we have events, no need for extra syscalls, but we might have to queue events */
637 /* we also clar the timeout if there are outstanding fdchanges */
638 /* the latter should only happen if both the sq and cq are full, most likely */
639 /* because we have a lot of event sources that immediately complete */
640 /* TODO: fdchacngecnt is always 0 because fd_reify does not have two buffers yet */
641 if (iouring_handle_cq (EV_A) || fdchangecnt)
642 timeout = EV_TS_CONST (0.);
643 else
644 /* no events, so maybe wait for some */
645 iouring_tfd_update (EV_A_ timeout);
646
647 /* only enter the kernel if we have something to submit, or we need to wait */
648 if (timeout || iouring_to_submit)
649 {
650 int res = iouring_enter (EV_A_ timeout);
651
652 if (ecb_expect_false (res < 0))
653 if (errno == EINTR)
654 /* ignore */;
655 else if (errno == EBUSY)
656 /* cq full, cannot submit - should be rare because we flush the cq first, so simply ignore */;
657 else
658 ev_syserr ("(libev) iouring setup");
659 else
660 iouring_handle_cq (EV_A);
661 }
662 }
663
664 inline_size
665 int
666 iouring_init (EV_P_ int flags)
667 {
668 iouring_entries = IOURING_INIT_ENTRIES;
669 iouring_max_entries = 0;
670
671 if (iouring_internal_init (EV_A) < 0)
672 {
673 iouring_internal_destroy (EV_A);
674 return 0;
675 }
676
677 ev_io_init (&iouring_tfd_w, iouring_tfd_cb, iouring_tfd, EV_READ);
678 ev_set_priority (&iouring_tfd_w, EV_MINPRI);
679 ev_io_start (EV_A_ &iouring_tfd_w);
680 ev_unref (EV_A); /* watcher should not keep loop alive */
681
682 backend_modify = iouring_modify;
683 backend_poll = iouring_poll;
684
685 return EVBACKEND_IOURING;
686 }
687
688 inline_size
689 void
690 iouring_destroy (EV_P)
691 {
692 iouring_internal_destroy (EV_A);
693 }
694