romenskiy2012/curl
1
0
Fork 0
mirror of https://github.com/curl/curl.git synced 2026-07-28 09:23:07 +03:00
Code Issues Projects Releases Packages Wiki Activity

socketpair: add eventfd and use SOCK_NONBLOCK for socketpair()

Browse source 
Currently, we use `pipe` for `wakeup_create`, which requires ***two***
file descriptors. Furthermore, given its complexity inside, `pipe` is a
bit heavyweight for just a simple event wait/notify mechanism.

`eventfd` would be a more suitable solution for this kind of scenario,
kernel also advocates for developers to use `eventfd` instead of `pipe`
in some simple use cases:

    Applications can use an eventfd file descriptor instead of a pipe
    (see pipe(2) in all cases where a pipe is used simply to signal
    events. The kernel overhead of an eventfd file descriptor is much
    lower than that of a pipe, and only one file descriptor is required
    (versus the two required for a pipe).

This change adds the new backend of `eventfd` for `wakeup_create` and
uses it where available, eliminating the overhead of `pipe`. Also, it
optimizes the `wakeup_create` to eliminate the system calls that make
file descriptors non-blocking by moving the logic of setting
non-blocking flags on file descriptors to `socketpair.c` and using
`SOCK_NONBLOCK` for `socketpair(2)`, `EFD_NONBLOCK` for `eventfd(2)`.

Ref:
https://man7.org/linux/man-pages/man7/pipe.7.html
https://man7.org/linux/man-pages/man2/eventfd.2.html
https://man7.org/linux/man-pages/man2/socketpair.2.html
https://www.gnu.org/software/gnulib/manual/html_node/eventfd.html

Closes #13874
This commit is contained in:
Andy Pan 2024-06-02 02:26:11 +08:00 • committed by Daniel Stenberg
parent b71916b859
commit 23fe1a52dc
No known key found for this signature in database
GPG key ID: 5CC908FDB71E12C2
10 changed files with 149 additions and 41 deletions
Download patch file Download diff file Expand all files Collapse all files

34
lib/asyn-thread.c
View file

@ -168,7 +168,7 @@ struct thread_sync_data {
duplicate */
#ifndef CURL_DISABLE_SOCKETPAIR
struct Curl_easy *data;
curl_socket_t sock_pair[2]; /* socket pair */
curl_socket_t sock_pair[2]; /* eventfd/pipes/socket pair */
#endif
int sock_error;
struct Curl_addrinfo *res;
@ -251,7 +251,7 @@ int init_thread_sync_data(struct thread_data *td,
#ifndef CURL_DISABLE_SOCKETPAIR
/* create socket pair or pipe */
if(wakeup_create(&tsd->sock_pair[0]) < 0) {
if(wakeup_create(tsd->sock_pair, FALSE) < 0) {
tsd->sock_pair[0] = CURL_SOCKET_BAD;
tsd->sock_pair[1] = CURL_SOCKET_BAD;
goto err_exit;
@ -302,6 +302,14 @@ query_complete(DWORD err, DWORD bytes, LPWSAOVERLAPPED overlapped)
struct Curl_addrinfo *ca;
struct Curl_addrinfo *cafirst = NULL;
struct Curl_addrinfo *calast = NULL;
#ifndef CURL_DISABLE_SOCKETPAIR
#ifdef USE_EVENTFD
const void *buf;
const uint64_t val = 1;
#else
char buf[1];
#endif
#endif
#ifdef __clang__
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wcast-align"
@ -421,11 +429,14 @@ query_complete(DWORD err, DWORD bytes, LPWSAOVERLAPPED overlapped)
}
else {
#ifndef CURL_DISABLE_SOCKETPAIR
char buf[1];
if(tsd->sock_pair[1] != CURL_SOCKET_BAD) {
/* DNS has been resolved, signal client task */
#ifdef USE_EVENTFD
buf = &val;
#else
buf[0] = 1;
if(swrite(tsd->sock_pair[1], buf, sizeof(buf)) < 0) {
#endif
/* DNS has been resolved, signal client task */
if(wakeup_write(tsd->sock_pair[1], buf, sizeof(buf)) < 0) {
/* update sock_erro to errno */
tsd->sock_error = SOCKERRNO;
}
@ -460,7 +471,12 @@ CURL_STDCALL getaddrinfo_thread(void *arg)
char service[12];
int rc;
#ifndef CURL_DISABLE_SOCKETPAIR
#ifdef USE_EVENTFD
const void *buf;
const uint64_t val = 1;
#else
char buf[1];
#endif
#endif
msnprintf(service, sizeof(service), "%d", tsd->port);
@ -486,9 +502,13 @@ CURL_STDCALL getaddrinfo_thread(void *arg)
else {
#ifndef CURL_DISABLE_SOCKETPAIR
if(tsd->sock_pair[1] != CURL_SOCKET_BAD) {
/* DNS has been resolved, signal client task */
#ifdef USE_EVENTFD
buf = &val;
#else
buf[0] = 1;
if(wakeup_write(tsd->sock_pair[1], buf, sizeof(buf)) < 0) {
#endif
/* DNS has been resolved, signal client task */
if(wakeup_write(tsd->sock_pair[1], buf, sizeof(buf)) < 0) {
/* update sock_erro to errno */
tsd->sock_error = SOCKERRNO;
}