diff options
Diffstat (limited to 'Utilities/cmlibuv/src/unix/async.c')
| -rw-r--r-- | Utilities/cmlibuv/src/unix/async.c | 253 |
1 files changed, 253 insertions, 0 deletions
diff --git a/Utilities/cmlibuv/src/unix/async.c b/Utilities/cmlibuv/src/unix/async.c new file mode 100644 index 0000000000..e1805c3237 --- /dev/null +++ b/Utilities/cmlibuv/src/unix/async.c @@ -0,0 +1,253 @@ +/* Copyright Joyent, Inc. and other Node contributors. All rights reserved. + * Permission is hereby granted, free of charge, to any person obtaining a copy + * of this software and associated documentation files (the "Software"), to + * deal in the Software without restriction, including without limitation the + * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or + * sell copies of the Software, and to permit persons to whom the Software is + * furnished to do so, subject to the following conditions: + * + * The above copyright notice and this permission notice shall be included in + * all copies or substantial portions of the Software. + * + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE + * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING + * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS + * IN THE SOFTWARE. + */ + +/* This file contains both the uv__async internal infrastructure and the + * user-facing uv_async_t functions. + */ + +#include "uv.h" +#include "internal.h" +#include "atomic-ops.h" + +#include <errno.h> +#include <stdio.h> /* snprintf() */ +#include <assert.h> +#include <stdlib.h> +#include <string.h> +#include <unistd.h> +#include <sched.h> /* sched_yield() */ + +#ifdef __linux__ +#include <sys/eventfd.h> +#endif + +static void uv__async_send(uv_loop_t* loop); +static int uv__async_start(uv_loop_t* loop); + + +int uv_async_init(uv_loop_t* loop, uv_async_t* handle, uv_async_cb async_cb) { + int err; + + err = uv__async_start(loop); + if (err) + return err; + + uv__handle_init(loop, (uv_handle_t*)handle, UV_ASYNC); + handle->async_cb = async_cb; + handle->pending = 0; + + QUEUE_INSERT_TAIL(&loop->async_handles, &handle->queue); + uv__handle_start(handle); + + return 0; +} + + +int uv_async_send(uv_async_t* handle) { + /* Do a cheap read first. */ + if (ACCESS_ONCE(int, handle->pending) != 0) + return 0; + + /* Tell the other thread we're busy with the handle. */ + if (cmpxchgi(&handle->pending, 0, 1) != 0) + return 0; + + /* Wake up the other thread's event loop. */ + uv__async_send(handle->loop); + + /* Tell the other thread we're done. */ + if (cmpxchgi(&handle->pending, 1, 2) != 1) + abort(); + + return 0; +} + + +/* Only call this from the event loop thread. */ +static int uv__async_spin(uv_async_t* handle) { + int i; + int rc; + + for (;;) { + /* 997 is not completely chosen at random. It's a prime number, acyclical + * by nature, and should therefore hopefully dampen sympathetic resonance. + */ + for (i = 0; i < 997; i++) { + /* rc=0 -- handle is not pending. + * rc=1 -- handle is pending, other thread is still working with it. + * rc=2 -- handle is pending, other thread is done. + */ + rc = cmpxchgi(&handle->pending, 2, 0); + + if (rc != 1) + return rc; + + /* Other thread is busy with this handle, spin until it's done. */ + cpu_relax(); + } + + /* Yield the CPU. We may have preempted the other thread while it's + * inside the critical section and if it's running on the same CPU + * as us, we'll just burn CPU cycles until the end of our time slice. + */ + sched_yield(); + } +} + + +void uv__async_close(uv_async_t* handle) { + uv__async_spin(handle); + QUEUE_REMOVE(&handle->queue); + uv__handle_stop(handle); +} + + +static void uv__async_io(uv_loop_t* loop, uv__io_t* w, unsigned int events) { + char buf[1024]; + ssize_t r; + QUEUE queue; + QUEUE* q; + uv_async_t* h; + + assert(w == &loop->async_io_watcher); + + for (;;) { + r = read(w->fd, buf, sizeof(buf)); + + if (r == sizeof(buf)) + continue; + + if (r != -1) + break; + + if (errno == EAGAIN || errno == EWOULDBLOCK) + break; + + if (errno == EINTR) + continue; + + abort(); + } + + QUEUE_MOVE(&loop->async_handles, &queue); + while (!QUEUE_EMPTY(&queue)) { + q = QUEUE_HEAD(&queue); + h = QUEUE_DATA(q, uv_async_t, queue); + + QUEUE_REMOVE(q); + QUEUE_INSERT_TAIL(&loop->async_handles, q); + + if (0 == uv__async_spin(h)) + continue; /* Not pending. */ + + if (h->async_cb == NULL) + continue; + + h->async_cb(h); + } +} + + +static void uv__async_send(uv_loop_t* loop) { + const void* buf; + ssize_t len; + int fd; + int r; + + buf = ""; + len = 1; + fd = loop->async_wfd; + +#if defined(__linux__) + if (fd == -1) { + static const uint64_t val = 1; + buf = &val; + len = sizeof(val); + fd = loop->async_io_watcher.fd; /* eventfd */ + } +#endif + + do + r = write(fd, buf, len); + while (r == -1 && errno == EINTR); + + if (r == len) + return; + + if (r == -1) + if (errno == EAGAIN || errno == EWOULDBLOCK) + return; + + abort(); +} + + +static int uv__async_start(uv_loop_t* loop) { + int pipefd[2]; + int err; + + if (loop->async_io_watcher.fd != -1) + return 0; + +#ifdef __linux__ + err = eventfd(0, EFD_CLOEXEC | EFD_NONBLOCK); + if (err < 0) + return UV__ERR(errno); + + pipefd[0] = err; + pipefd[1] = -1; +#else + err = uv__make_pipe(pipefd, UV_NONBLOCK_PIPE); + if (err < 0) + return err; +#endif + + uv__io_init(&loop->async_io_watcher, uv__async_io, pipefd[0]); + uv__io_start(loop, &loop->async_io_watcher, POLLIN); + loop->async_wfd = pipefd[1]; + + return 0; +} + + +int uv__async_fork(uv_loop_t* loop) { + if (loop->async_io_watcher.fd == -1) /* never started */ + return 0; + + uv__async_stop(loop); + + return uv__async_start(loop); +} + + +void uv__async_stop(uv_loop_t* loop) { + if (loop->async_io_watcher.fd == -1) + return; + + if (loop->async_wfd != -1) { + if (loop->async_wfd != loop->async_io_watcher.fd) + uv__close(loop->async_wfd); + loop->async_wfd = -1; + } + + uv__io_stop(loop, &loop->async_io_watcher, POLLIN); + uv__close(loop->async_io_watcher.fd); + loop->async_io_watcher.fd = -1; +} |