view contrib/chg/procutil.c @ 42006:111de135fc76

branchcache: add attributes to track which nodes are verified

Half of the cost of loading branchcache comes from verifiying all the nodes it
has. We don't need to verify all the nodes in all the cases. Sometimes we need
to verify only a set of nodes for a set of branches. We can ignore nodes of
other branches as we are not going to read them.

This patch introduces two attributes to branchcache class. _verifiedbranches is
a set which will tell the branches for which it's head nodes are verified.
_closedverified is a boolean which will tell whether all closednodes are
verified or not.

Another idea which I had was to keep a set of nodes which are verified, but it
will be more ugly and difficult to track things on node level.

Differential Revision: https://phab.mercurial-scm.org/D6156

/*
 * Utilities about process handling - signal and subprocess (ex. pager)
 *
 * Copyright (c) 2011 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 <stdio.h>
#include <string.h>
#include <sys/wait.h>
#include <unistd.h>

#include "procutil.h"
#include "util.h"

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

static void forwardsignal(int sig)
{
	assert(peerpid > 0);
	if (kill(peerpid, sig) < 0) {
		abortmsgerrno("cannot kill %d", peerpid);
	}
	debugmsg("forward signal %d", sig);
}

static void forwardsignaltogroup(int sig)
{
	/* prefer kill(-pgid, sig), fallback to pid if pgid is invalid */
	pid_t killpid = peerpgid > 1 ? -peerpgid : peerpid;
	if (kill(killpid, sig) < 0) {
		abortmsgerrno("cannot kill %d", killpid);
	}
	debugmsg("forward signal %d to %d", sig, killpid);
}

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

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

error:
	abortmsgerrno("failed to handle stop signal");
}

static void handlechildsignal(int sig UNUSED_)
{
	if (peerpid == 0 || pagerpid == 0) {
		return;
	}
	/* if pager exits, notify the server with SIGPIPE immediately.
	 * otherwise the server won't get SIGPIPE if it does not write
	 * anything. (issue5278) */
	if (waitpid(pagerpid, NULL, WNOHANG) == pagerpid) {
		kill(peerpid, SIGPIPE);
	}
}

void setupsignalhandler(pid_t pid, pid_t pgid)
{
	if (pid <= 0) {
		return;
	}
	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) {
		goto error;
	}
	if (sigaction(SIGHUP, &sa, NULL) < 0) {
		goto error;
	}
	if (sigaction(SIGINT, &sa, NULL) < 0) {
		goto error;
	}

	/* 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) {
		goto error;
	}

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

	return;

error:
	abortmsgerrno("failed to set up signal handlers");
}

void 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) {
		goto error;
	}

	if (sigaction(SIGHUP, &sa, NULL) < 0) {
		goto error;
	}
	if (sigaction(SIGTERM, &sa, NULL) < 0) {
		goto error;
	}
	if (sigaction(SIGWINCH, &sa, NULL) < 0) {
		goto error;
	}
	if (sigaction(SIGCONT, &sa, NULL) < 0) {
		goto error;
	}
	if (sigaction(SIGTSTP, &sa, NULL) < 0) {
		goto error;
	}
	if (sigaction(SIGCHLD, &sa, NULL) < 0) {
		goto error;
	}

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

	peerpid = 0;
	return;

error:
	abortmsgerrno("failed to restore signal handlers");
}

/* This implementation is based on hgext/pager.py (post 369741ef7253)
 * Return 0 if pager is not started, or pid of the pager */
pid_t setuppager(const char *pagercmd, const char *envp[])
{
	assert(pagerpid == 0);
	if (!pagercmd) {
		return 0;
	}

	int pipefds[2];
	if (pipe(pipefds) < 0) {
		return 0;
	}
	pid_t pid = fork();
	if (pid < 0) {
		goto error;
	}
	if (pid > 0) {
		close(pipefds[0]);
		if (dup2(pipefds[1], fileno(stdout)) < 0) {
			goto error;
		}
		if (isatty(fileno(stderr))) {
			if (dup2(pipefds[1], fileno(stderr)) < 0) {
				goto error;
			}
		}
		close(pipefds[1]);
		pagerpid = pid;
		return pid;
	} else {
		dup2(pipefds[0], fileno(stdin));
		close(pipefds[0]);
		close(pipefds[1]);

		int r =
		    execle("/bin/sh", "/bin/sh", "-c", pagercmd, NULL, envp);
		if (r < 0) {
			abortmsgerrno("cannot start pager '%s'", pagercmd);
		}
		return 0;
	}

error:
	close(pipefds[0]);
	close(pipefds[1]);
	abortmsgerrno("failed to prepare pager");
	return 0;
}

void waitpager(void)
{
	if (pagerpid == 0) {
		return;
	}

	/* close output streams to notify the pager its input ends */
	fclose(stdout);
	fclose(stderr);
	while (1) {
		pid_t ret = waitpid(pagerpid, NULL, 0);
		if (ret == -1 && errno == EINTR) {
			continue;
		}
		break;
	}
}