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Comparing libev/ev_linuxaio.c (file contents):
Revision 1.1 by root, Thu Jun 20 22:44:59 2019 UTC vs.
Revision 1.21 by root, Mon Jun 24 20:44:15 2019 UTC

… …
35 * and other provisions required by the GPL. If you do not delete the 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 36 * provisions above, a recipient may use your version of this file under
37 * either the BSD or the GPL. 37 * either the BSD or the GPL.
38 */ 38 */
39 39
40#define EPOLL_FALLBACK 1
41
40#include <sys/time.h> /* actually linux/time.h, but we must assume they are compatible */ 42#include <sys/time.h> /* actually linux/time.h, but we must assume they are compatible */
43#include <poll.h>
41#include <linux/aio_abi.h> 44#include <linux/aio_abi.h>
42 45
46#if EPOLL_FALLBACK
47# include <sys/epoll.h>
48#endif
49
43/* we try to fill 4kn pages exactly. 50/* we try to fill 4kB pages exactly.
44 * the ring buffer header is 32 bytes, every io event is 32 bytes. 51 * the ring buffer header is 32 bytes, every io event is 32 bytes.
45 * the kernel takes the io event number, doubles it, adds 2, adds the ring buffer 52 * the kernel takes the io event number, doubles it, adds 2, adds the ring buffer.
46 * so the calculation below will use "exactly" 8kB for the ring buffer 53 * therefore the calculation below will use "exactly" 4kB for the ring buffer
47 */ 54 */
48#define EV_LINUXAIO_DEPTH (256 / 2 - 2 - 1) /* max. number of io events per batch */ 55#define EV_LINUXAIO_DEPTH (128 / 2 - 2 - 1) /* max. number of io events per batch */
49 56
50/*****************************************************************************/ 57/*****************************************************************************/
51/* syscall wrapdadoop */ 58/* syscall wrapdadoop - this section has the raw syscall definitions */
52 59
53#include <sys/syscall.h> /* no glibc wrappers */ 60#include <sys/syscall.h> /* no glibc wrappers */
54 61
55/* aio_abi.h is not verioned in any way, so we cannot test for its existance */ 62/* aio_abi.h is not versioned in any way, so we cannot test for its existance */
56#define IOCB_CMD_POLL 5 63#define IOCB_CMD_POLL 5
57 64
58/* taken from linux/fs/aio.c */ 65/* taken from linux/fs/aio.c */
59#define AIO_RING_MAGIC 0xa10a10a1 66#define AIO_RING_MAGIC 0xa10a10a1
60#define AIO_RING_INCOMPAT_FEATURES 0 67#define AIO_RING_INCOMPAT_FEATURES 0
… …
71 unsigned header_length; /* size of aio_ring */ 78 unsigned header_length; /* size of aio_ring */
72 79
73 struct io_event io_events[0]; 80 struct io_event io_events[0];
74}; 81};
75 82
76static int 83inline_size
84int
77ev_io_setup (unsigned nr_events, aio_context_t *ctx_idp) 85evsys_io_setup (unsigned nr_events, aio_context_t *ctx_idp)
78{ 86{
79 return syscall (SYS_io_setup, nr_events, ctx_idp); 87 return syscall (SYS_io_setup, nr_events, ctx_idp);
80} 88}
81 89
82static int 90inline_size
91int
83ev_io_destroy (aio_context_t ctx_id) 92evsys_io_destroy (aio_context_t ctx_id)
84{ 93{
85 return syscall (SYS_io_destroy, ctx_id); 94 return syscall (SYS_io_destroy, ctx_id);
86} 95}
87 96
88static int 97inline_size
98int
89ev_io_submit (aio_context_t ctx_id, long nr, struct iocb *cbp[]) 99evsys_io_submit (aio_context_t ctx_id, long nr, struct iocb *cbp[])
90{ 100{
91 return syscall (SYS_io_submit, ctx_id, nr, cbp); 101 return syscall (SYS_io_submit, ctx_id, nr, cbp);
92} 102}
93 103
94static int 104inline_size
105int
95ev_io_cancel (aio_context_t ctx_id, struct iocb *cbp, struct io_event *result) 106evsys_io_cancel (aio_context_t ctx_id, struct iocb *cbp, struct io_event *result)
96{ 107{
97 return syscall (SYS_io_cancel, ctx_id, cbp, result); 108 return syscall (SYS_io_cancel, ctx_id, cbp, result);
98} 109}
99 110
100static int 111inline_size
112int
101ev_io_getevents (aio_context_t ctx_id, long min_nr, long nr, struct io_event *events, struct timespec *timeout) 113evsys_io_getevents (aio_context_t ctx_id, long min_nr, long nr, struct io_event *events, struct timespec *timeout)
102{ 114{
103 return syscall (SYS_io_getevents, ctx_id, min_nr, nr, events, timeout); 115 return syscall (SYS_io_getevents, ctx_id, min_nr, nr, events, timeout);
104} 116}
105
106typedef void (*ev_io_cb) (long nr, struct io_event *events);
107 117
108/*****************************************************************************/ 118/*****************************************************************************/
109/* actual backed implementation */ 119/* actual backed implementation */
110 120
111/* two iocbs for every fd, one for read, one for write */ 121/* we use out own wrapper structure in acse we ever want to do something "clever" */
112typedef struct aniocb 122typedef struct aniocb
113{ 123{
114 struct iocb io; 124 struct iocb io;
115 /*int inuse;*/ 125 /*int inuse;*/
116} *ANIOCBP; 126} *ANIOCBP;
117 127
118inline_size 128inline_size
119void 129void
120linuxaio_array_needsize_iocbp (ANIOCBP *base, int count) 130linuxaio_array_needsize_iocbp (ANIOCBP *base, int count)
121{ 131{
122 /* TODO: quite the overhead to allocate every iocb separately */ 132 /* TODO: quite the overhead to allocate every iocb separately, maybe use our own alocator? */
123 while (count--) 133 while (count--)
124 { 134 {
125 *base = (ANIOCBP)ev_malloc (sizeof (**base)); 135 *base = (ANIOCBP)ev_malloc (sizeof (**base));
136 /* TODO: full zero initialize required? */
126 memset (*base, 0, sizeof (**base)); 137 memset (*base, 0, sizeof (**base));
127 /* would be nice to initialize fd/data as well */ 138 /* would be nice to initialize fd/data as well, but array_needsize API doesn't support that */
128 (*base)->io.aio_lio_opcode = IOCB_CMD_POLL; 139 (*base)->io.aio_lio_opcode = IOCB_CMD_POLL;
129 ++base; 140 ++base;
130 } 141 }
131} 142}
132 143
144ecb_cold
133static void 145static void
134linuxaio_free_iocbp (EV_P) 146linuxaio_free_iocbp (EV_P)
135{ 147{
136 while (linuxaio_iocbpmax--) 148 while (linuxaio_iocbpmax--)
137 ev_free (linuxaio_iocbps [linuxaio_iocbpmax]); 149 ev_free (linuxaio_iocbps [linuxaio_iocbpmax]);
138 150
139 linuxaio_iocbpmax = 0; 151 linuxaio_iocbpmax = 0; /* next resize will completely reallocate the array, at some overhead */
140} 152}
141 153
142static void 154static void
143linuxaio_modify (EV_P_ int fd, int oev, int nev) 155linuxaio_modify (EV_P_ int fd, int oev, int nev)
144{ 156{
145 /* TODO: full zero initialize required? */
146 array_needsize (ANIOCBP, linuxaio_iocbps, linuxaio_iocbpmax, fd + 1, linuxaio_array_needsize_iocbp); 157 array_needsize (ANIOCBP, linuxaio_iocbps, linuxaio_iocbpmax, fd + 1, linuxaio_array_needsize_iocbp);
147 struct aniocb *iocb = linuxaio_iocbps [fd]; 158 struct aniocb *iocb = linuxaio_iocbps [fd];
148 159
160#if EPOLL_FALLBACK
161 if (iocb->io.aio_reqprio < 0)
162 {
163 epoll_ctl (backend_fd, EPOLL_CTL_DEL, fd, 0);
164 iocb->io.aio_reqprio = 0;
165 }
166#endif
167
149 if (iocb->io.aio_buf) 168 if (iocb->io.aio_buf)
150 ev_io_cancel (linuxaio_ctx, &iocb->io, (void *)0); 169 evsys_io_cancel (linuxaio_ctx, &iocb->io, (struct io_event *)0); /* always returns an error relevant kernels */
151 170
152 if (nev) 171 if (nev)
153 { 172 {
154 iocb->io.aio_data = fd; 173 iocb->io.aio_data = fd;
155 iocb->io.aio_fildes = fd; 174 iocb->io.aio_fildes = fd;
… …
163 array_needsize (struct iocb *, linuxaio_submits, linuxaio_submitmax, linuxaio_submitcnt, array_needsize_noinit); 182 array_needsize (struct iocb *, linuxaio_submits, linuxaio_submitmax, linuxaio_submitcnt, array_needsize_noinit);
164 linuxaio_submits [linuxaio_submitcnt - 1] = &iocb->io; 183 linuxaio_submits [linuxaio_submitcnt - 1] = &iocb->io;
165 } 184 }
166} 185}
167 186
187#if EPOLL_FALLBACK
188
189static void
190linuxaio_rearm_epoll (EV_P_ struct iocb *iocb, int op)
191{
192 struct epoll_event eev;
193
194 eev.events = EPOLLONESHOT;
195 if (iocb->aio_buf & POLLIN ) eev.events |= EPOLLIN ;
196 if (iocb->aio_buf & POLLOUT) eev.events |= EPOLLOUT;
197 eev.data.fd = iocb->aio_fildes;
198
199 if (epoll_ctl (backend_fd, op, iocb->aio_fildes, &eev) < 0)
200 ev_syserr ("(libeio) linuxaio epoll_ctl");
201}
202
203static void
204linuxaio_epoll_cb (EV_P_ struct ev_io *w, int revents)
205{
206 struct epoll_event events[16];
207
208 for (;;)
209 {
210 int idx;
211 int res = epoll_wait (backend_fd, events, sizeof (events) / sizeof (events [0]), 0);
212
213 if (expect_false (res < 0))
214 ev_syserr ("(libev) linuxaio epoll_wait");
215 else if (!res)
216 break;
217
218 for (idx = res; idx--; )
219 {
220 int fd = events [idx].data.fd;
221 uint32_t ev = events [idx].events;
222
223 assert (("libev: iocb fd must be in-bounds", fd >= 0 && fd < anfdmax));
224
225 linuxaio_rearm_epoll (EV_A_ &linuxaio_iocbps [fd]->io, EPOLL_CTL_MOD);
226
227 fd_event (EV_A_ fd,
228 (ev & (EPOLLOUT | EPOLLERR | EPOLLHUP) ? EV_WRITE : 0)
229 | (ev & (EPOLLIN | EPOLLERR | EPOLLHUP) ? EV_READ : 0));
230 }
231
232 if (res < sizeof (events) / sizeof (events [0]))
233 break;
234 }
235}
236
237#endif
238
168static void 239static void
169linuxaio_parse_events (EV_P_ struct io_event *ev, int nr) 240linuxaio_parse_events (EV_P_ struct io_event *ev, int nr)
170{ 241{
171 while (nr) 242 while (nr)
172 { 243 {
173 int fd = ev->data; 244 int fd = ev->data;
174 int res = ev->res; 245 int res = ev->res;
175 246
176 assert (("libev: iocb fd must be in-bounds", fd >= 0 && fd < anfdxmax)); 247 assert (("libev: iocb fd must be in-bounds", fd >= 0 && fd < anfdmax));
177 248
178 /* linux aio is oneshot: rearm fd */ 249 /* linux aio is oneshot: rearm fd. TODO: this does more work than needed */
179 linuxaio_iocbps [fd]->io.aio_buf = 0; 250 linuxaio_iocbps [fd]->io.aio_buf = 0;
180 anfds [fd].events = 0; 251 anfds [fd].events = 0;
181 fd_change (EV_A_ fd, 0); 252 fd_change (EV_A_ fd, 0);
182 253
183 /* feed events, we do not expect or handle POLLNVAL */ 254 /* feed events, we do not expect or handle POLLNVAL */
184 if (ecb_expect_false (res & POLLNVAL))
185 fd_kill (EV_A_ fd);
186 else
187 fd_event ( 255 fd_event (
188 EV_A_ 256 EV_A_
189 fd, 257 fd,
190 (res & (POLLOUT | POLLERR | POLLHUP) ? EV_WRITE : 0) 258 (res & (POLLOUT | POLLERR | POLLHUP) ? EV_WRITE : 0)
191 | (res & (POLLIN | POLLERR | POLLHUP) ? EV_READ : 0) 259 | (res & (POLLIN | POLLERR | POLLHUP) ? EV_READ : 0)
192 ); 260 );
193 261
194 --nr; 262 --nr;
195 ++ev; 263 ++ev;
196 } 264 }
197} 265}
… …
200static int 268static int
201linuxaio_get_events_from_ring (EV_P) 269linuxaio_get_events_from_ring (EV_P)
202{ 270{
203 struct aio_ring *ring = (struct aio_ring *)linuxaio_ctx; 271 struct aio_ring *ring = (struct aio_ring *)linuxaio_ctx;
204 272
273 /* the kernel reads and writes both of these variables, */
274 /* as a C extension, we assume that volatile use here */
275 /* both makes reads atomic and once-only */
276 unsigned head = *(volatile unsigned *)&ring->head;
277 unsigned tail = *(volatile unsigned *)&ring->tail;
278
279 if (head == tail)
280 return 0;
281
282 /* bail out if the ring buffer doesn't match the expected layout */
283 if (expect_false (ring->magic != AIO_RING_MAGIC)
284 || ring->incompat_features != AIO_RING_INCOMPAT_FEATURES
285 || ring->header_length != sizeof (struct aio_ring)) /* TODO: or use it to find io_event[0]? */
286 return 0;
287
288 /* make sure the events up to tail are visible */
205 ECB_MEMORY_FENCE_ACQUIRE; 289 ECB_MEMORY_FENCE_ACQUIRE;
206
207 unsigned head = ring->head;
208 unsigned tail = *(volatile unsigned *)&ring->tail;
209
210 if (ring->magic != AIO_RING_MAGIC
211 || ring->incompat_features != AIO_RING_INCOMPAT_FEATURES
212 || ring->header_length != sizeof (struct aio_ring) /* TODO: or use it to find io_event[0]? */
213 || head == tail)
214 return 0;
215 290
216 /* parse all available events, but only once, to avoid starvation */ 291 /* parse all available events, but only once, to avoid starvation */
217 if (tail > head) /* normal case around */ 292 if (tail > head) /* normal case around */
218 linuxaio_parse_events (EV_A_ ring->io_events + head, tail - head); 293 linuxaio_parse_events (EV_A_ ring->io_events + head, tail - head);
219 else
220 {
221 /* wrapped around */ 294 else /* wrapped around */
295 {
222 linuxaio_parse_events (EV_A_ ring->io_events + head, ring->nr - head); 296 linuxaio_parse_events (EV_A_ ring->io_events + head, ring->nr - head);
223 linuxaio_parse_events (EV_A_ ring->io_events, tail); 297 linuxaio_parse_events (EV_A_ ring->io_events, tail);
224 } 298 }
225 299
226 ring->head = tail; 300 /* TODO: we only need a compiler barrier here, not a read fence */
301 ECB_MEMORY_FENCE_RELEASE;
302 /* as an extension to C, we hope that the volatile will make this atomic and once-only */
303 *(volatile unsigned *)&ring->head = tail;
304 /* make sure kernel can see our new head value - probably not required */
305 ECB_MEMORY_FENCE_RELEASE;
227 306
228 return 1; 307 return 1;
229} 308}
230 309
231/* read at least one event from kernel, or timeout */ 310/* read at least one event from kernel, or timeout */
232inline_size 311inline_size
233void 312void
234linuxaio_get_events (EV_P_ ev_tstamp timeout) 313linuxaio_get_events (EV_P_ ev_tstamp timeout)
235{ 314{
236 struct timespec ts; 315 struct timespec ts;
237 struct io_event ioev; 316 struct io_event ioev[1];
238 int res; 317 int res;
239 318
240 if (linuxaio_get_events_from_ring (EV_A)) 319 if (linuxaio_get_events_from_ring (EV_A))
241 return; 320 return;
242 321
243 /* no events, so wait for at least one, then poll ring buffer again */ 322 /* no events, so wait for at least one, then poll ring buffer again */
244 /* this degraded to one event per loop iteration */ 323 /* this degrades to one event per loop iteration */
245 /* if the ring buffer changes layout, but so be it */ 324 /* if the ring buffer changes layout, but so be it */
325
326 EV_RELEASE_CB;
246 327
247 ts.tv_sec = (long)timeout; 328 ts.tv_sec = (long)timeout;
248 ts.tv_nsec = (long)((timeout - ts.tv_sec) * 1e9); 329 ts.tv_nsec = (long)((timeout - ts.tv_sec) * 1e9);
249 330
250 res = ev_io_getevents (linuxaio_ctx, 1, 1, &ioev, &ts); 331 res = evsys_io_getevents (linuxaio_ctx, 1, sizeof (ioev) / sizeof (ioev [0]), ioev, &ts);
332
333 EV_ACQUIRE_CB;
251 334
252 if (res < 0) 335 if (res < 0)
336 if (errno == EINTR)
337 /* ignored */;
338 else
253 ev_syserr ("(libev) io_getevents"); 339 ev_syserr ("(libev) linuxaio io_getevents");
254 else if (res) 340 else if (res)
255 { 341 {
256 /* at least one event received, handle it and any remaining ones in the ring buffer */ 342 /* at least one event received, handle it and any remaining ones in the ring buffer */
257 linuxaio_parse_events (EV_A_ &ioev, 1); 343 linuxaio_parse_events (EV_A_ ioev, res);
258 linuxaio_get_events_from_ring (EV_A); 344 linuxaio_get_events_from_ring (EV_A);
259 } 345 }
260} 346}
261 347
262static void 348static void
… …
269 /* io_submit might return less than the requested number of iocbs */ 355 /* io_submit might return less than the requested number of iocbs */
270 /* this is, afaics, only because of errors, but we go by the book and use a loop, */ 356 /* this is, afaics, only because of errors, but we go by the book and use a loop, */
271 /* which allows us to pinpoint the errornous iocb */ 357 /* which allows us to pinpoint the errornous iocb */
272 for (submitted = 0; submitted < linuxaio_submitcnt; ) 358 for (submitted = 0; submitted < linuxaio_submitcnt; )
273 { 359 {
360#if 0
361 int res;
362 if (linuxaio_submits[submitted]->aio_fildes == backend_fd)
363 res = evsys_io_submit (linuxaio_ctx, 1, linuxaio_submits + submitted);
364 else
365 { res = -1; errno = EINVAL; };
366#else
274 int res = ev_io_submit (linuxaio_ctx, linuxaio_submitcnt - submitted, linuxaio_submits + submitted); 367 int res = evsys_io_submit (linuxaio_ctx, linuxaio_submitcnt - submitted, linuxaio_submits + submitted);
368#endif
275 369
276 if (res < 0) 370 if (expect_false (res < 0))
277 if (errno == EAGAIN) 371 if (errno == EAGAIN)
278 { 372 {
279 /* This happens when the ring buffer is full, at least. I assume this means 373 /* This happens when the ring buffer is full, at least. I assume this means
280 * that the event was queued synchronously during io_submit, and thus 374 * that the event was queued synchronously during io_submit, and thus
281 * the buffer overflowd. 375 * the buffer overflowed.
282 * In this case, we just try next loop iteration. 376 * In this case, we just try in next loop iteration.
377 * This should not result in a few fds taking priority, as the interface
378 * is one-shot, and we submit iocb's in a round-robin fashion.
379 * TODO: maybe make "submitted" persistent, so we don't have to memmove?
283 */ 380 */
381 if (ecb_expect_false (submitted))
382 {
284 memcpy (linuxaio_submits, linuxaio_submits + submitted, (linuxaio_submitcnt - submitted) * sizeof (*linuxaio_submits)); 383 memmove (linuxaio_submits, linuxaio_submits + submitted, (linuxaio_submitcnt - submitted) * sizeof (*linuxaio_submits));
285 linuxaio_submitcnt -= submitted; 384 linuxaio_submitcnt -= submitted;
385 }
386
286 timeout = 0; 387 timeout = 0;
287 break; 388 break;
288 } 389 }
390#if EPOLL_FALLBACK
391 else if (errno == EINVAL)
392 {
393 /* This happens for unsupported fds, officially, but in my testing,
394 * also randomly happens for supported fds. We fall back to good old
395 * poll() here, under the assumption that this is a very rare case.
396 * See https://lore.kernel.org/patchwork/patch/1047453/ to see
397 * discussion about such a case (ttys) where polling for POLLIN
398 * fails but POLLIN|POLLOUT works.
399 */
400 struct iocb *iocb = linuxaio_submits [submitted];
401
402 linuxaio_rearm_epoll (EV_A_ linuxaio_submits [submitted], EPOLL_CTL_ADD);
403 iocb->aio_reqprio = -1; /* mark iocb as epoll */
404
405 res = 1; /* skip this iocb */
406 }
407#endif
408 else if (errno == EBADF)
409 {
410 fd_kill (EV_A_ linuxaio_submits [submitted]->aio_fildes);
411
412 res = 1; /* skip this iocb */
413 }
289 else 414 else
290 /* TODO: we get EAGAIN when the ring buffer is full for some reason */
291 /* TODO: should we always just try next time? */
292 ev_syserr ("(libev) io_submit"); 415 ev_syserr ("(libev) linuxaio io_submit");
293 416
294 submitted += res; 417 submitted += res;
295 } 418 }
296 419
297 linuxaio_submitcnt = 0; 420 linuxaio_submitcnt = 0;
… …
304inline_size 427inline_size
305int 428int
306linuxaio_init (EV_P_ int flags) 429linuxaio_init (EV_P_ int flags)
307{ 430{
308 /* would be great to have a nice test for IOCB_CMD_POLL instead */ 431 /* would be great to have a nice test for IOCB_CMD_POLL instead */
309 if (ev_linux_version () < 0x041200) /* 4.18 introduced IOCB_CMD_POLL */ 432 /* also: test some semi-common fd types, such as files and ttys in recommended_backends */
433#if EPOLL_FALLBACK
434 /* 4.19 made epoll work */
435 if (ev_linux_version () < 0x041300)
310 return 0; 436 return 0;
311 437#else
312 if (ev_io_setup (EV_LINUXAIO_DEPTH, &linuxaio_ctx) < 0) 438 /* 4.18 introduced IOCB_CMD_POLL */
439 if (ev_linux_version () < 0x041200)
313 return 0; 440 return 0;
441#endif
442
443 linuxaio_ctx = 0;
444 if (evsys_io_setup (EV_LINUXAIO_DEPTH, &linuxaio_ctx) < 0)
445 return 0;
446
447#if EPOLL_FALLBACK
448 backend_fd = ev_epoll_create ();
449 if (backend_fd < 0)
450 {
451 evsys_io_destroy (linuxaio_ctx);
452 return 0;
453 }
454
455 ev_io_init (EV_A_ &linuxaio_epoll_w, linuxaio_epoll_cb, backend_fd, EV_READ);
456 ev_set_priority (&linuxaio_epoll_w, EV_MAXPRI);
457 ev_io_start (EV_A_ &linuxaio_epoll_w);
458 ev_unref (EV_A); /* watcher should not keep loop alive */
459#endif
314 460
315 backend_modify = linuxaio_modify; 461 backend_modify = linuxaio_modify;
316 backend_poll = linuxaio_poll; 462 backend_poll = linuxaio_poll;
317 463
318 linuxaio_iocbpmax = 0; 464 linuxaio_iocbpmax = 0;
… …
327 473
328inline_size 474inline_size
329void 475void
330linuxaio_destroy (EV_P) 476linuxaio_destroy (EV_P)
331{ 477{
478#if EPOLL_FALLBACK
479 close (backend_fd);
480#endif
332 linuxaio_free_iocbp (EV_A); 481 linuxaio_free_iocbp (EV_A);
333 ev_io_destroy (linuxaio_ctx); 482 evsys_io_destroy (linuxaio_ctx);
334} 483}
335 484
336inline_size 485inline_size
337void 486void
338linuxaio_fork (EV_P) 487linuxaio_fork (EV_P)
339{ 488{
340 abort ();//D 489 /* this frees all iocbs, which is very heavy-handed */
341} 490 linuxaio_destroy (EV_A);
491 linuxaio_submitcnt = 0; /* all pointers were invalidated */
342 492
493 linuxaio_ctx = 0;
494 while (evsys_io_setup (EV_LINUXAIO_DEPTH, &linuxaio_ctx) < 0)
495 ev_syserr ("(libev) linuxaio io_setup");
496
497#if EPOLL_FALLBACK
498 while ((backend_fd = ev_epoll_create ()) < 0)
499 ev_syserr ("(libev) linuxaio epoll_create");
500
501 ev_io_stop (EV_A_ &linuxaio_epoll_w);
502 ev_io_init (EV_A_ &linuxaio_epoll_w, linuxaio_epoll_cb, backend_fd, EV_READ);
503 ev_io_start (EV_A_ &linuxaio_epoll_w);
504#endif
505
506 fd_rearm_all (EV_A);
507}
508

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