Because it is very hard to make fork(2) from threaded process safe (we are

limited to async-signal safe functions in the child process), move all hooks
execution to the main (non-threaded) process.

Do it by maintaining connection (socketpair) between child and parent
and sending events from the child to parent, so it can execute the hook.

This is step in right direction for others reasons too. For example there is
one less problem to drop privs in worker processes.

MFC after:	2 weeks
Obtained from:	Wheel Systems Sp. z o.o. http://www.wheelsystems.com

sbin/hastd/Makefile

@@ -5,7 +5,7 @@
 PROG=	hastd
 SRCS=	activemap.c
 SRCS+=	control.c
-SRCS+=	ebuf.c
+SRCS+=	ebuf.c event.c
 SRCS+=	hast_proto.c hastd.c hooks.c
 SRCS+=	metadata.c
 SRCS+=	nv.c

sbin/hastd/hast.h

@@ -181,6 +181,8 @@ struct hast_resource {
 	pid_t	hr_workerpid;
 	/* Control connection between parent and child. */
 	struct proto_conn *hr_ctrl;
+	/* Events from child to parent. */
+	struct proto_conn *hr_event;
 
 	/* Activemap structure. */
 	struct activemap *hr_amp;

sbin/hastd/hastd.c

@@ -52,6 +52,7 @@ __FBSDID("$FreeBSD$");
 #include <pjdlog.h>
 
 #include "control.h"
+#include "event.h"
 #include "hast.h"
 #include "hast_proto.h"
 #include "hastd.h"
@@ -158,6 +159,11 @@ child_exit(void)
 		    role2str(res->hr_role));
 		child_exit_log(pid, status);
 		proto_close(res->hr_ctrl);
+		res->hr_ctrl = NULL;
+		if (res->hr_event != NULL) {
+			proto_close(res->hr_event);
+			res->hr_event = NULL;
+		}
 		res->hr_workerpid = 0;
 		if (res->hr_role == HAST_ROLE_PRIMARY) {
 			/*
@@ -624,9 +630,10 @@ listen_accept(void)
 static void
 main_loop(void)
 {
-	fd_set rfds;
-	int cfd, lfd, maxfd, ret;
+	struct hast_resource *res;
 	struct timeval timeout;
+	int fd, maxfd, ret;
+	fd_set rfds;
 
 	timeout.tv_sec = REPORT_INTERVAL;
 	timeout.tv_usec = 0;
@@ -646,14 +653,20 @@ main_loop(void)
 			hastd_reload();
 		}
 
-		cfd = proto_descriptor(cfg->hc_controlconn);
-		lfd = proto_descriptor(cfg->hc_listenconn);
-		maxfd = cfd > lfd ? cfd : lfd;
-
 		/* Setup descriptors for select(2). */
 		FD_ZERO(&rfds);
-		FD_SET(cfd, &rfds);
-		FD_SET(lfd, &rfds);
+		maxfd = fd = proto_descriptor(cfg->hc_controlconn);
+		FD_SET(fd, &rfds);
+		fd = proto_descriptor(cfg->hc_listenconn);
+		FD_SET(fd, &rfds);
+		maxfd = fd > maxfd ? fd : maxfd;
+		TAILQ_FOREACH(res, &cfg->hc_resources, hr_next) {
+			if (res->hr_event == NULL)
+				continue;
+			fd = proto_descriptor(res->hr_event);
+			FD_SET(fd, &rfds);
+			maxfd = fd > maxfd ? fd : maxfd;
+		}
 
 		ret = select(maxfd + 1, &rfds, NULL, NULL, &timeout);
 		if (ret == 0)
@@ -665,10 +678,21 @@ main_loop(void)
 			pjdlog_exit(EX_OSERR, "select() failed");
 		}
 
-		if (FD_ISSET(cfd, &rfds))
+		if (FD_ISSET(proto_descriptor(cfg->hc_controlconn), &rfds))
 			control_handle(cfg);
-		if (FD_ISSET(lfd, &rfds))
+		if (FD_ISSET(proto_descriptor(cfg->hc_listenconn), &rfds))
 			listen_accept();
+		TAILQ_FOREACH(res, &cfg->hc_resources, hr_next) {
+			if (res->hr_event == NULL)
+				continue;
+			if (FD_ISSET(proto_descriptor(res->hr_event), &rfds)) {
+				if (event_recv(res) == 0)
+					continue;
+				/* The worker process exited? */
+				proto_close(res->hr_event);
+				res->hr_event = NULL;
+			}
+		}
 	}
 }
 

sbin/hastd/primary.c

@@ -58,6 +58,7 @@ __FBSDID("$FreeBSD$");
 #include <rangelock.h>
 
 #include "control.h"
+#include "event.h"
 #include "hast.h"
 #include "hast_proto.h"
 #include "hastd.h"
@@ -225,12 +226,6 @@ static void *ggate_send_thread(void *arg);
 static void *sync_thread(void *arg);
 static void *guard_thread(void *arg);
 
-static void
-dummy_sighandler(int sig __unused)
-{
-	/* Nothing to do. */
-}
-
 static void
 cleanup(struct hast_resource *res)
 {
@@ -429,8 +424,6 @@ init_environment(struct hast_resource *res __unused)
 	/*
 	 * Turn on signals handling.
 	 */
-	/* Because SIGCHLD is ignored by default, setup dummy handler for it. */
-	PJDLOG_VERIFY(signal(SIGCHLD, dummy_sighandler) != SIG_ERR);
 	PJDLOG_VERIFY(sigfillset(&mask) == 0);
 	PJDLOG_VERIFY(sigprocmask(SIG_SETMASK, &mask, NULL) == 0);
 }
@@ -672,11 +665,11 @@ init_remote(struct hast_resource *res, struct proto_conn **inp,
 		res->hr_remotein = in;
 		res->hr_remoteout = out;
 	}
-	hook_exec(res->hr_exec, "connect", res->hr_name, NULL);
+	event_send(res, EVENT_CONNECT);
 	return (true);
 close:
 	if (errmsg != NULL && strcmp(errmsg, "Split-brain condition!") == 0)
-		hook_exec(res->hr_exec, "split-brain", res->hr_name, NULL);
+		event_send(res, EVENT_SPLITBRAIN);
 	proto_close(out);
 	if (in != NULL)
 		proto_close(in);
@@ -774,6 +767,14 @@ hastd_primary(struct hast_resource *res)
 		pjdlog_exit(EX_OSERR,
 		    "Unable to create control sockets between parent and child");
 	}
+	/*
+	 * Create communication channel between child and parent.
+	 */
+	if (proto_client("socketpair://", &res->hr_event) < 0) {
+		KEEP_ERRNO((void)pidfile_remove(pfh));
+		pjdlog_exit(EX_OSERR,
+		    "Unable to create event sockets between child and parent");
+	}
 
 	pid = fork();
 	if (pid < 0) {
@@ -783,6 +784,8 @@ hastd_primary(struct hast_resource *res)
 
 	if (pid > 0) {
 		/* This is parent. */
+		/* Declare that we are receiver. */
+		proto_recv(res->hr_event, NULL, 0);
 		res->hr_workerpid = pid;
 		return;
 	}
@@ -797,7 +800,9 @@ hastd_primary(struct hast_resource *res)
 	signal(SIGHUP, SIG_DFL);
 	signal(SIGCHLD, SIG_DFL);
 
-	hook_init();
+	/* Declare that we are sender. */
+	proto_send(res->hr_event, NULL, 0);
+
 	init_local(res);
 	if (real_remote(res) && init_remote(res, NULL, NULL))
 		sync_start();
@@ -896,7 +901,7 @@ remote_close(struct hast_resource *res, int ncomp)
 	 */
 	sync_stop();
 
-	hook_exec(res->hr_exec, "disconnect", res->hr_name, NULL);
+	event_send(res, EVENT_DISCONNECT);
 }
 
 /*
@@ -1512,7 +1517,7 @@ sync_thread(void *arg __unused)
 			pjdlog_info("Synchronization interrupted. "
 			    "%jd bytes synchronized so far.",
 			    (intmax_t)synced);
-			hook_exec(res->hr_exec, "syncintr", res->hr_name, NULL);
+			event_send(res, EVENT_SYNCINTR);
 		}
 		while (!sync_inprogress) {
 			dorewind = true;
@@ -1545,8 +1550,7 @@ sync_thread(void *arg __unused)
 				pjdlog_info("Synchronization started. %ju bytes to go.",
 				    (uintmax_t)(res->hr_extentsize *
 				    activemap_ndirty(res->hr_amp)));
-				hook_exec(res->hr_exec, "syncstart",
-				    res->hr_name, NULL);
+				event_send(res, EVENT_SYNCSTART);
 			}
 		}
 		if (offset < 0) {
@@ -1563,8 +1567,7 @@ sync_thread(void *arg __unused)
 					pjdlog_info("Synchronization complete. "
 					    "%jd bytes synchronized.",
 					    (intmax_t)synced);
-					hook_exec(res->hr_exec, "syncdone",
-					    res->hr_name, NULL);
+					event_send(res, EVENT_SYNCDONE);
 				}
 				mtx_lock(&metadata_lock);
 				res->hr_syncsrc = HAST_SYNCSRC_UNDEF;
@@ -1950,7 +1953,6 @@ guard_thread(void *arg)
 	PJDLOG_VERIFY(sigaddset(&mask, SIGHUP) == 0);
 	PJDLOG_VERIFY(sigaddset(&mask, SIGINT) == 0);
 	PJDLOG_VERIFY(sigaddset(&mask, SIGTERM) == 0);
-	PJDLOG_VERIFY(sigaddset(&mask, SIGCHLD) == 0);
 
 	timeout.tv_nsec = 0;
 	signo = -1;
@@ -1969,7 +1971,6 @@ guard_thread(void *arg)
 		default:
 			break;
 		}
-		hook_check(signo == SIGCHLD);
 
 		pjdlog_debug(2, "remote_guard: Checking connections.");
 		now = time(NULL);

sbin/hastd/secondary.c

@@ -54,6 +54,7 @@ __FBSDID("$FreeBSD$");
 #include <pjdlog.h>
 
 #include "control.h"
+#include "event.h"
 #include "hast.h"
 #include "hast_proto.h"
 #include "hastd.h"
@@ -325,7 +326,7 @@ init_remote(struct hast_resource *res, struct nv *nvin)
 	if (res->hr_secondary_localcnt > res->hr_primary_remotecnt &&
 	     res->hr_primary_localcnt > res->hr_secondary_remotecnt) {
 		/* Exit on split-brain. */
-		hook_exec(res->hr_exec, "split-brain", res->hr_name, NULL);
+		event_send(res, EVENT_SPLITBRAIN);
 		exit(EX_CONFIG);
 	}
 }
@@ -345,6 +346,14 @@ hastd_secondary(struct hast_resource *res, struct nv *nvin)
 		pjdlog_exit(EX_OSERR,
 		    "Unable to create control sockets between parent and child");
 	}
+	/*
+	 * Create communication channel between child and parent.
+	 */
+	if (proto_client("socketpair://", &res->hr_event) < 0) {
+		KEEP_ERRNO((void)pidfile_remove(pfh));
+		pjdlog_exit(EX_OSERR,
+		    "Unable to create event sockets between child and parent");
+	}
 
 	pid = fork();
 	if (pid < 0) {
@@ -358,6 +367,8 @@ hastd_secondary(struct hast_resource *res, struct nv *nvin)
 		res->hr_remotein = NULL;
 		proto_close(res->hr_remoteout);
 		res->hr_remoteout = NULL;
+		/* Declare that we are receiver. */
+		proto_recv(res->hr_event, NULL, 0);
 		res->hr_workerpid = pid;
 		return;
 	}
@@ -372,17 +383,19 @@ hastd_secondary(struct hast_resource *res, struct nv *nvin)
 	signal(SIGHUP, SIG_DFL);
 	signal(SIGCHLD, SIG_DFL);
 
+	/* Declare that we are sender. */
+	proto_send(res->hr_event, NULL, 0);
+
 	/* Error in setting timeout is not critical, but why should it fail? */
 	if (proto_timeout(res->hr_remotein, 0) < 0)
 		pjdlog_errno(LOG_WARNING, "Unable to set connection timeout");
 	if (proto_timeout(res->hr_remoteout, res->hr_timeout) < 0)
 		pjdlog_errno(LOG_WARNING, "Unable to set connection timeout");
 
-	hook_init();
 	init_local(res);
 	init_remote(res, nvin);
 	init_environment();
-	hook_exec(res->hr_exec, "connect", res->hr_name, NULL);
+	event_send(res, EVENT_CONNECT);
 
 	error = pthread_create(&td, NULL, recv_thread, res);
 	assert(error == 0);
@@ -515,7 +528,7 @@ secondary_exit(int exitcode, const char *fmt, ...)
 	va_start(ap, fmt);
 	pjdlogv_errno(LOG_ERR, fmt, ap);
 	va_end(ap);
-	hook_exec(gres->hr_exec, "disconnect", gres->hr_name, NULL);
+	event_send(gres, EVENT_DISCONNECT);
 	exit(exitcode);
 }