rust/chg/src/sighandlers.c

shelve: stop passing list of files to revert

It seems to work just fine to not specify any files here. I suspect it
looked the way it did for historical reasons. It apparently used to
use merge instead of rebase until 1d7a36ff2615 (shelve: use rebase
instead of merge (issue4068), 2013-10-23) and it makes sense to want
to restrict the set of files then.

I noticed this because of the files.extend(shelvectx.p1().files()). If
the working copy was clean before, then shelvectx.p1() will be the
working copy parent and that ended up adding all the files in that
set. In our Google-internal Mercurial setup (including a FUSE) that
was very noticeably slow when the working copy parent happened to have
many files in large directories.

This patch doesn't yet remove the call to shelvectx.p1().files(). We
also use that set for deciding what to back up. I'm pretty sure it's
safe to back up only the set of files we already back even if we no
longer restrict the set of files to revert, so this patch should be
safe on its own. Regardless, the next patch will delegate the
backing-up to cmdutil.revert().

Incidentally, this also gets rid of a repo.pathto() that I had earlier
wanted to get rid of.

Differential Revision: https://phab.mercurial-scm.org/D6173

/*
 * 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;
}