/* 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.
*/
#include "uv.h"
#include "internal.h"
#include <errno.h>
#include <assert.h>
#include <stdlib.h>
#include <unistd.h>
static int uv__async_init(uv_loop_t* loop);
static void uv__async_io(uv_loop_t* loop, uv__io_t* handle, int events);
__attribute__((always_inline))
static int uv__async_make_pending(volatile sig_atomic_t* ptr) {
/* Do a cheap read first. */
if (*ptr)
return 1;
/* Micro-optimization: use atomic memory operations to detect if we've been
* preempted by another thread and don't have to make an expensive syscall.
* This speeds up the heavily contended case by about 1-2% and has little
* if any impact on the non-contended case.
*
* Use XCHG instead of the CMPXCHG that __sync_val_compare_and_swap() emits
* on x86, it's about 4x faster. It probably makes zero difference in the
* grand scheme of things but I'm OCD enough not to let this one pass.
*/
#if __i386__ || __x86_64__
{
unsigned int val = 1;
__asm__ __volatile__("xchgl %0, %1" : "+r" (val) : "m" (*ptr));
return val != 0;
}
#elif __GNUC__ > 4 || __GNUC__ == 4 && __GNUC_MINOR__ >= 1 /* gcc >= 4.1 */
return __sync_val_compare_and_swap(ptr, 0, 1) != 0;
#else
*ptr = 1;
return 0;
#endif
}
int uv_async_init(uv_loop_t* loop, uv_async_t* handle, uv_async_cb async_cb) {
if (uv__async_init(loop))
return uv__set_sys_error(loop, errno);
uv__handle_init(loop, (uv_handle_t*)handle, UV_ASYNC);
handle->async_cb = async_cb;
handle->pending = 0;
ngx_queue_insert_tail(&loop->async_handles, &handle->queue);
uv__handle_start(handle);
return 0;
}
int uv_async_send(uv_async_t* handle) {
int r;
if (uv__async_make_pending(&handle->pending))
return 0; /* already pending */
do
r = write(handle->loop->async_pipefd[1], "x", 1);
while (r == -1 && errno == EINTR);
if (r == -1 && errno != EAGAIN && errno != EWOULDBLOCK)
return uv__set_sys_error(handle->loop, errno);
return 0;
}
void uv__async_close(uv_async_t* handle) {
ngx_queue_remove(&handle->queue);
uv__handle_stop(handle);
}
static int uv__async_init(uv_loop_t* loop) {
if (loop->async_pipefd[0] != -1)
return 0;
if (uv__make_pipe(loop->async_pipefd, UV__F_NONBLOCK))
return -1;
uv__io_init(&loop->async_watcher,
uv__async_io,
loop->async_pipefd[0],
UV__IO_READ);
uv__io_start(loop, &loop->async_watcher);
return 0;
}
static void uv__async_io(uv_loop_t* loop, uv__io_t* handle, int events) {
char buf[1024];
ngx_queue_t* q;
uv_async_t* h;
ssize_t r;
while (1) {
r = read(loop->async_pipefd[0], buf, sizeof(buf));
if (r == sizeof(buf))
continue;
if (r != -1)
break;
if (errno == EAGAIN || errno == EWOULDBLOCK)
break;
if (errno == EINTR)
continue;
abort();
}
ngx_queue_foreach(q, &loop->async_handles) {
h = ngx_queue_data(q, uv_async_t, queue);
if (!h->pending) continue;
h->pending = 0;
h->async_cb(h, 0);
}
}