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219 | static int |
219 | static int |
220 | linuxaio_get_events_from_ring (EV_P) |
220 | linuxaio_get_events_from_ring (EV_P) |
221 | { |
221 | { |
222 | struct aio_ring *ring = (struct aio_ring *)linuxaio_ctx; |
222 | struct aio_ring *ring = (struct aio_ring *)linuxaio_ctx; |
223 | |
223 | |
224 | unsigned head = ring->head; |
224 | /* the kernel reads and writes both of these variables, */ |
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225 | /* as a C extension, we assume that volatile use here */ |
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226 | /* both makes reads atomic and once-only */ |
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227 | unsigned head = *(volatile unsigned *)&ring->head; |
225 | unsigned tail = *(volatile unsigned *)&ring->tail; |
228 | unsigned tail = *(volatile unsigned *)&ring->tail; |
226 | |
229 | |
227 | if (head == tail) |
230 | if (head == tail) |
228 | return 0; |
231 | return 0; |
229 | |
232 | |
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243 | { |
246 | { |
244 | linuxaio_parse_events (EV_A_ ring->io_events + head, ring->nr - head); |
247 | linuxaio_parse_events (EV_A_ ring->io_events + head, ring->nr - head); |
245 | linuxaio_parse_events (EV_A_ ring->io_events, tail); |
248 | linuxaio_parse_events (EV_A_ ring->io_events, tail); |
246 | } |
249 | } |
247 | |
250 | |
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251 | /* TODO: we only need a compiler barrier here, not a read fence */ |
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252 | ECB_MEMORY_FENCE_RELEASE; |
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253 | /* as an extension to C, we hope that the volatile will make this atomic and once-only */ |
248 | *(volatile unsigned *)&ring->head = tail; |
254 | *(volatile unsigned *)&ring->head = tail; |
249 | /* make sure kernel can see our new head value - probably not required */ |
255 | /* make sure kernel can see our new head value - probably not required */ |
250 | ECB_MEMORY_FENCE_RELEASE; |
256 | ECB_MEMORY_FENCE_RELEASE; |
251 | |
257 | |
252 | return 1; |
258 | return 1; |
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332 | break; |
338 | break; |
333 | } |
339 | } |
334 | #if EPOLL_FALLBACK |
340 | #if EPOLL_FALLBACK |
335 | else if (errno == EINVAL) |
341 | else if (errno == EINVAL) |
336 | { |
342 | { |
337 | /* This hapΓΌpens for unsupported fds, officially, but in my testing, |
343 | /* This happens for unsupported fds, officially, but in my testing, |
338 | * also randomly happens for supported fds. We fall back to good old |
344 | * also randomly happens for supported fds. We fall back to good old |
339 | * poll() here, under the assumption that this is a very rare case. |
345 | * poll() here, under the assumption that this is a very rare case. |
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346 | * See https://lore.kernel.org/patchwork/patch/1047453/ for evidence |
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347 | * that the problem is known, but ignored. |
340 | */ |
348 | */ |
341 | struct iocb *iocb = linuxaio_submits [submitted]; |
349 | struct iocb *iocb = linuxaio_submits [submitted]; |
342 | res = 1; /* skip this iocb */ |
350 | res = 1; /* skip this iocb */ |
343 | |
351 | |
344 | linuxaio_rearm_epoll (EV_A_ iocb, EPOLL_CTL_ADD); |
352 | linuxaio_rearm_epoll (EV_A_ iocb, EPOLL_CTL_ADD); |
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400 | int |
408 | int |
401 | linuxaio_init (EV_P_ int flags) |
409 | linuxaio_init (EV_P_ int flags) |
402 | { |
410 | { |
403 | /* would be great to have a nice test for IOCB_CMD_POLL instead */ |
411 | /* would be great to have a nice test for IOCB_CMD_POLL instead */ |
404 | /* also: test some semi-common fd types, such as files and ttys in recommended_backends */ |
412 | /* also: test some semi-common fd types, such as files and ttys in recommended_backends */ |
405 | if (ev_linux_version () < 0x041200) /* 4.18 introduced IOCB_CMD_POLL */ |
413 | #if EPOLL_FALLBACK |
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414 | /* 4.19 made epoll work */ |
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415 | if (ev_linux_version () < 0x041300) |
406 | return 0; |
416 | return 0; |
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417 | #else |
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418 | /* 4.18 introduced IOCB_CMD_POLL */ |
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419 | if (ev_linux_version () < 0x041200) |
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420 | return 0; |
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421 | #endif |
407 | |
422 | |
408 | linuxaio_ctx = 0; |
423 | linuxaio_ctx = 0; |
409 | if (ev_io_setup (EV_LINUXAIO_DEPTH, &linuxaio_ctx) < 0) |
424 | if (ev_io_setup (EV_LINUXAIO_DEPTH, &linuxaio_ctx) < 0) |
410 | return 0; |
425 | return 0; |
411 | |
426 | |
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417 | return 0; |
432 | return 0; |
418 | } |
433 | } |
419 | |
434 | |
420 | ev_io_init (EV_A_ &linuxaio_epoll_w, linuxaio_epoll_cb, backend_fd, EV_READ); |
435 | ev_io_init (EV_A_ &linuxaio_epoll_w, linuxaio_epoll_cb, backend_fd, EV_READ); |
421 | ev_io_start (EV_A_ &linuxaio_epoll_w); |
436 | ev_io_start (EV_A_ &linuxaio_epoll_w); |
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437 | ev_unref (EV_A); /* watcher should not keep loop alive */ |
422 | #endif |
438 | #endif |
423 | |
439 | |
424 | backend_modify = linuxaio_modify; |
440 | backend_modify = linuxaio_modify; |
425 | backend_poll = linuxaio_poll; |
441 | backend_poll = linuxaio_poll; |
426 | |
442 | |
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462 | ev_syserr ("(libev) linuxaio epoll_create"); |
478 | ev_syserr ("(libev) linuxaio epoll_create"); |
463 | |
479 | |
464 | ev_io_stop (EV_A_ &linuxaio_epoll_w); |
480 | ev_io_stop (EV_A_ &linuxaio_epoll_w); |
465 | ev_io_init (EV_A_ &linuxaio_epoll_w, linuxaio_epoll_cb, backend_fd, EV_READ); |
481 | ev_io_init (EV_A_ &linuxaio_epoll_w, linuxaio_epoll_cb, backend_fd, EV_READ); |
466 | ev_io_start (EV_A_ &linuxaio_epoll_w); |
482 | ev_io_start (EV_A_ &linuxaio_epoll_w); |
467 | ev_unref (EV_A); /* watcher should not keep loop alive */ |
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468 | #endif |
483 | #endif |
469 | |
484 | |
470 | fd_rearm_all (EV_A); |
485 | fd_rearm_all (EV_A); |
471 | } |
486 | } |
472 | |
487 | |