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Fork as early as possible

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If fork is requested, we fork as early as possible, way before anything
is initialized. This way, we don't need to do the gymnastics to make
OpenGL work properly across fork.

Signed-off-by: Yuxuan Shui <yshuiv7@gmail.com>
This commit is contained in:
Yuxuan Shui
2019-02-08 01:27:46 +00:00
parent fec43acfaa
commit 5fffb6f3f6
5 changed files with 80 additions and 76 deletions
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131
src/compton.c
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@ -9,6 +9,7 @@
*
*/
#include <fcntl.h>
#include <stdio.h>
#include <string.h>
#include <inttypes.h>
@ -2028,49 +2029,6 @@ register_cm(session_t *ps) {
return true;
}
/**
* Fork program to background and disable all I/O streams.
*/
static inline bool
fork_after(session_t *ps) {
if (getppid() == 1)
return true;
#ifdef CONFIG_OPENGL
// GLX context must be released and reattached on fork
if (glx_has_context(ps) && !glXMakeCurrent(ps->dpy, XCB_NONE, NULL)) {
log_fatal("Failed to detach GLX context.");
return false;
}
#endif
int pid = fork();
if (-1 == pid) {
log_fatal("fork() failed.");
return false;
}
if (pid > 0) _exit(0);
setsid();
#ifdef CONFIG_OPENGL
if (glx_has_context(ps)
&& !glXMakeCurrent(ps->dpy, get_tgt_window(ps), ps->psglx->context)) {
log_fatal("Failed to make GLX context current.");
return false;
}
#endif
if (!freopen("/dev/null", "r", stdin)) {
log_fatal("freopen() failed.");
return false;
}
return true;
}
/**
* Write PID to a file.
*/
@ -2485,14 +2443,16 @@ reset_enable(EV_P_ ev_signal *w, int revents) {
/**
* Initialize a session.
*
* @param ps_old old session, from which the function will take the X
* connection, then free it
* @param argc number of commandline arguments
* @param argv commandline arguments
* @param dpy the X Display
* @param config_file the path to the config file
* @param all_xerros whether we should report all X errors
* @param fork whether we will fork after initialization
*/
static session_t *
session_init(int argc, char **argv, Display *dpy, bool all_xerrors,
const char *config_file) {
session_init(int argc, char **argv, Display *dpy, const char *config_file,
bool all_xerrors, bool fork) {
static const session_t s_def = {
.backend_data = NULL,
.dpy = NULL,
@ -2518,7 +2478,6 @@ session_init(int argc, char **argv, Display *dpy, bool all_xerrors,
.glx_no_stencil = false,
.mark_wmwin_focused = false,
.mark_ovredir_focused = false,
.fork_after_register = false,
.detect_rounded_corners = false,
.resize_damage = 0,
.unredir_if_possible = false,
@ -2779,6 +2738,7 @@ session_init(int argc, char **argv, Display *dpy, bool all_xerrors,
log_info("Switching to log file: %s", ps->o.logpath);
log_remove_target_tls(stderr_logger);
log_add_target_tls(l);
stderr_logger = NULL;
} else {
log_error("Failed to setup log file %s, I will keep using stderr", ps->o.logpath);
}
@ -3023,23 +2983,12 @@ session_init(int argc, char **argv, Display *dpy, bool all_xerrors,
free(e);
}
// Fork to background, if asked
if (ps->o.fork_after_register) {
if (!fork_after(ps)) {
session_destroy(ps);
return NULL;
}
}
// Redirect output stream
if (ps->o.fork_after_register) {
if (!freopen("/dev/null", "w", stdout) || !freopen("/dev/null", "w", stderr)) {
log_fatal("Failed to redirect stdout/stderr to /dev/null");
exit(1);
}
}
write_pid(ps);
if (fork && stderr_logger) {
// Remove the stderr logger if we will fork
log_remove_target_tls(stderr_logger);
}
return ps;
}
@ -3232,11 +3181,41 @@ main(int argc, char **argv) {
int exit_code;
char *config_file = NULL;
bool all_xerrors = 0;
if (get_early_config(argc, argv, &config_file, &all_xerrors, &exit_code)) {
bool all_xerrors = false, need_fork = false;
if (get_early_config(argc, argv, &config_file, &all_xerrors, &need_fork, &exit_code)) {
return exit_code;
}
int pfds[2];
if (need_fork) {
if (pipe2(pfds, O_CLOEXEC)) {
perror("pipe2");
return 1;
}
auto pid = fork();
if (pid < 0) {
perror("fork");
return 1;
}
if (pid > 0) {
// We are the parent
close(pfds[1]);
// We wait for the child to tell us it has finished initialization
// by sending us something via the pipe.
int tmp;
if (read(pfds[0], &tmp, sizeof tmp) <= 0) {
// Failed to read, the child has most likely died
// We can probably waitpid() here.
return 1;
} else {
// We are done
return 0;
}
}
// We are the child
close(pfds[0]);
}
sigset_t sigmask;
sigemptyset(&sigmask);
const struct sigaction int_action = {
@ -3256,11 +3235,29 @@ main(int argc, char **argv) {
XSetEventQueueOwner(dpy, XCBOwnsEventQueue);
do {
ps_g = session_init(argc, argv, dpy, all_xerrors, config_file);
ps_g = session_init(argc, argv, dpy, config_file, all_xerrors, need_fork);
if (!ps_g) {
log_fatal("Failed to create new compton session.");
return 1;
}
if (need_fork) {
// Finishing up daemonization
// Close files
if (fclose(stdout) || fclose(stderr) || fclose(stdin)) {
log_fatal("Failed to close standard input/output");
return 1;
}
// Make us the session and process group leader so we don't get killed when
// our parent die.
setsid();
// Notify the parent that we are done. This might cause the parent to quit,
// so only do this after setsid()
int tmp = 1;
write(pfds[1], &tmp, sizeof tmp);
close(pfds[1]);
// We only do this once
need_fork = false;
}
session_run(ps_g);
quit = ps_g->quit;
session_destroy(ps_g);