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Added new signal handler for SIGUSR2. When init receives SIGUSR2

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it closes (and leaves closed) the named pipe /run/initctl. This
can be used to make sure init does not have any files open. However,
it also means we cannot switch run levels or bring down the system.
The pipe can be re-opened by sending init the SIGUSR1 signal.

Updated the man pages for initctl and init to include this information.
This commit is contained in:
Jesse Smith
2018-04-17 19:44:50 -03:00
parent f09da9cb55
commit 272f112c98
4 changed files with 43 additions and 4 deletions
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23
src/init.c
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@ -1116,7 +1116,11 @@ pid_t spawn(CHILD *ch, int *res)
close(0);
close(1);
close(2);
if (pipe_fd >= 0) close(pipe_fd);
if (pipe_fd >= 0)
{
close(pipe_fd);
pipe_fd = -1;
}
sigprocmask(SIG_SETMASK, &omask, NULL);
@ -2172,6 +2176,7 @@ void re_exec(void)
DELSET(got_signals, SIGCHLD);
DELSET(got_signals, SIGHUP);
DELSET(got_signals, SIGUSR1);
DELSET(got_signals, SIGUSR2);
/*
* That should be cleaned.
@ -2368,9 +2373,10 @@ void check_init_fifo(void)
}
/*
* Now finally try to open /run/initctl
* Now finally try to open /run/initctl if pipe_fd is -1
* if it is -2, then we leave it closed
*/
if (pipe_fd < 0) {
if (pipe_fd == -1) {
if ((pipe_fd = open(INIT_FIFO, O_RDWR|O_NONBLOCK)) >= 0) {
fstat(pipe_fd, &st);
if (!S_ISFIFO(st.st_mode)) {
@ -2471,7 +2477,7 @@ void check_init_fifo(void)
/*
* We come here if the pipe couldn't be opened.
*/
if (pipe_fd < 0) pause();
if (pipe_fd == -1) pause();
}
@ -2682,6 +2688,14 @@ void process_signals()
pipe_fd = -1;
DELSET(got_signals, SIGUSR1);
}
else if (ISMEMBER(got_signals, SIGUSR2)) {
/* SIGUSR1 mean close the pipe and leave it closed */
INITDBG(L_VB, "got SIGUSR2");
if (pipe_fd)
close(pipe_fd);
pipe_fd = -2;
DELSET(got_signals, SIGUSR2);
}
}
/*
@ -2740,6 +2754,7 @@ void init_main(void)
SETSIG(sa, SIGPWR, signal_handler, 0);
SETSIG(sa, SIGWINCH, signal_handler, 0);
SETSIG(sa, SIGUSR1, signal_handler, 0);
SETSIG(sa, SIGUSR2, signal_handler, 0);
SETSIG(sa, SIGSTOP, stop_handler, SA_RESTART);
SETSIG(sa, SIGTSTP, stop_handler, SA_RESTART);
SETSIG(sa, SIGCONT, cont_handler, SA_RESTART);