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linux: reduce file descriptor count of async pipe

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Reopen one of the pipe descriptors as read/write through the procfs.
Allows us to close the original pipe file descriptors, saving a file
descriptor on kernels that don't support eventfd(2).
This commit is contained in:
Ben Noordhuis 2014-04-09 04:46:43 +02:00 committed by Fedor Indutny
parent 39fee8ea42
commit 86831fe99c
1 changed files with 28 additions and 6 deletions
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34
src/unix/async.c
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@ -26,6 +26,7 @@
#include "internal.h"
#include <errno.h>
#include <stdio.h> /* snprintf() */
#include <assert.h>
#include <stdlib.h>
#include <string.h>
@ -217,8 +218,28 @@ int uv__async_start(uv_loop_t* loop, struct uv__async* wa, uv__async_cb cb) {
pipefd[0] = err;
pipefd[1] = -1;
}
else if (err == -ENOSYS)
else if (err == -ENOSYS) {
err = uv__make_pipe(pipefd, UV__F_NONBLOCK);
#if defined(__linux__)
/* Save a file descriptor by opening one of the pipe descriptors as
* read/write through the procfs. That file descriptor can then
* function as both ends of the pipe.
*/
if (err == 0) {
char buf[32];
int fd;
snprintf(buf, sizeof(buf), "/proc/self/fd/%d", pipefd[0]);
fd = uv__open_cloexec(buf, O_RDWR);
if (fd != -1) {
uv__close(pipefd[0]);
uv__close(pipefd[1]);
pipefd[0] = fd;
pipefd[1] = fd;
}
}
#endif
}
if (err < 0)
return err;
@ -236,14 +257,15 @@ void uv__async_stop(uv_loop_t* loop, struct uv__async* wa) {
if (wa->io_watcher.fd == -1)
return;
if (wa->wfd != -1) {
if (wa->wfd != wa->io_watcher.fd)
uv__close(wa->wfd);
wa->wfd = -1;
}
uv__io_stop(loop, &wa->io_watcher, UV__POLLIN);
uv__close(wa->io_watcher.fd);
wa->io_watcher.fd = -1;
if (wa->wfd != -1) {
uv__close(wa->wfd);
wa->wfd = -1;
}
}