view rust/chg/src/sighandlers.c @ 47643:11f834e7177d

pyoxidizer: add hooks to inject extra python packages and install files

We need this type of hook to inject our internal extension and resource files
at Google. Presumably this could be useful to others, so instead of trying to
carry an internal patch we've done this in a modular way that should be of
value upstream.

I'm extremely puzzled by the behavior of glob() on Windows, and I'll
be filing at least one (probably two) bugs upstream about it.

Differential Revision: https://phab.mercurial-scm.org/D11092

/*
 * Signal handlers for cHg
 *
 * Copyright 2011, 2018 Yuya Nishihara <[e-mail]>
 *
 * This software may be used and distributed according to the terms of the
 * GNU General Public License version 2 or any later version.
 */

#include <assert.h>
#include <errno.h>
#include <signal.h>
#include <string.h>
#include <unistd.h>

static pid_t peerpgid = 0;
static pid_t peerpid = 0;

static void forwardsignal(int sig)
{
	assert(peerpid > 0);
	(void)kill(peerpid, sig);
}

static void forwardsignaltogroup(int sig)
{
	/* prefer kill(-pgid, sig), fallback to pid if pgid is invalid */
	pid_t killpid = peerpgid > 1 ? -peerpgid : peerpid;
	(void)kill(killpid, sig);
}

static void handlestopsignal(int sig)
{
	sigset_t unblockset, oldset;
	struct sigaction sa, oldsa;
	if (sigemptyset(&unblockset) < 0) {
		return;
	}
	if (sigaddset(&unblockset, sig) < 0) {
		return;
	}
	memset(&sa, 0, sizeof(sa));
	sa.sa_handler = SIG_DFL;
	sa.sa_flags = SA_RESTART;
	if (sigemptyset(&sa.sa_mask) < 0) {
		return;
	}

	forwardsignal(sig);
	if (raise(sig) < 0) { /* resend to self */
		return;
	}
	if (sigaction(sig, &sa, &oldsa) < 0) {
		return;
	}
	if (sigprocmask(SIG_UNBLOCK, &unblockset, &oldset) < 0) {
		return;
	}
	/* resent signal will be handled before sigprocmask() returns */
	if (sigprocmask(SIG_SETMASK, &oldset, NULL) < 0) {
		return;
	}
	if (sigaction(sig, &oldsa, NULL) < 0) {
		return;
	}
}

/*
 * Installs signal handlers.
 *
 * Returns 0 on success, -1 on error and errno is set appropriately.
 * Installed handlers wouldn't be cleaned up on error.
 */
int setupsignalhandler(pid_t pid, pid_t pgid)
{
	if (pid <= 0) {
		errno = EINVAL;
		return -1;
	}
	peerpid = pid;
	peerpgid = (pgid <= 1 ? 0 : pgid);

	struct sigaction sa;
	memset(&sa, 0, sizeof(sa));

	/* deadly signals meant to be sent to a process group:
	 * - SIGHUP: usually generated by the kernel, when termination of a
	 *   process causes that process group to become orphaned
	 * - SIGINT: usually generated by the terminal */
	sa.sa_handler = forwardsignaltogroup;
	sa.sa_flags = SA_RESTART;
	if (sigemptyset(&sa.sa_mask) < 0) {
		return -1;
	}
	if (sigaction(SIGHUP, &sa, NULL) < 0) {
		return -1;
	}
	if (sigaction(SIGINT, &sa, NULL) < 0) {
		return -1;
	}

	/* terminate frontend by double SIGTERM in case of server freeze */
	sa.sa_handler = forwardsignal;
	sa.sa_flags |= SA_RESETHAND;
	if (sigaction(SIGTERM, &sa, NULL) < 0) {
		return -1;
	}

	/* notify the worker about window resize events */
	sa.sa_flags = SA_RESTART;
	if (sigaction(SIGWINCH, &sa, NULL) < 0) {
		return -1;
	}
	/* forward user-defined signals */
	if (sigaction(SIGUSR1, &sa, NULL) < 0) {
		return -1;
	}
	if (sigaction(SIGUSR2, &sa, NULL) < 0) {
		return -1;
	}
	/* propagate job control requests to worker */
	sa.sa_handler = forwardsignal;
	sa.sa_flags = SA_RESTART;
	if (sigaction(SIGCONT, &sa, NULL) < 0) {
		return -1;
	}
	sa.sa_handler = handlestopsignal;
	sa.sa_flags = SA_RESTART;
	if (sigaction(SIGTSTP, &sa, NULL) < 0) {
		return -1;
	}

	return 0;
}

/*
 * Restores signal handlers to the default, and masks SIGINT.
 *
 * Returns 0 on success, -1 on error and errno is set appropriately.
 */
int restoresignalhandler(void)
{
	struct sigaction sa;
	memset(&sa, 0, sizeof(sa));
	sa.sa_handler = SIG_DFL;
	sa.sa_flags = SA_RESTART;
	if (sigemptyset(&sa.sa_mask) < 0) {
		return -1;
	}

	if (sigaction(SIGHUP, &sa, NULL) < 0) {
		return -1;
	}
	if (sigaction(SIGTERM, &sa, NULL) < 0) {
		return -1;
	}
	if (sigaction(SIGWINCH, &sa, NULL) < 0) {
		return -1;
	}
	if (sigaction(SIGCONT, &sa, NULL) < 0) {
		return -1;
	}
	if (sigaction(SIGTSTP, &sa, NULL) < 0) {
		return -1;
	}

	/* ignore Ctrl+C while shutting down to make pager exits cleanly */
	sa.sa_handler = SIG_IGN;
	if (sigaction(SIGINT, &sa, NULL) < 0) {
		return -1;
	}

	peerpid = 0;
	return 0;
}