Synchronize commands and update properly with a lock (towards

resolving #1458175 and #1504036):
(update_lock): New.
(update_shed): Initialize it.
(update_wait, dispatch): Take exclusive update_lock around the update,
shared update_lock around commands.  This makes the update block until
all aborted commands terminated and gave up their lock.  Remove the
cheesy and unsafe two second wait for commands to finish.  It also
makes player threads block before executing commands while the update
is pending, removing the need to fail commands then.  So don't.

include/server.h

@@ -39,6 +39,7 @@
 extern int shutdown_pending;
 extern int update_pending;
 extern empth_sem_t *update_sem;
+extern empth_rwlock_t *update_lock;
 extern time_t update_time;
 extern int updating_mob;
 

src/lib/player/dispatch.c

@@ -88,10 +88,7 @@ dispatch(char *buf, char *redir)
 	pr("Command not implemented\n");
 	return 0;
     }
-    if (update_pending) {
+    empth_rwlock_rdlock(update_lock);
-	pr("Update in progress...command failed\n");
-	return 0;
-    }
     if (redir) {
 	prredir(redir);
 	uprnf(buf);
@@ -113,6 +110,7 @@ dispatch(char *buf, char *redir)
 	logerror("%s: returned bad value", command->c_form);
 	break;
     }
+    empth_rwlock_unlock(update_lock);
     player->command = 0;
     return 0;
 }

src/server/update.c

@@ -48,6 +48,7 @@
 #include "server.h"
 
 empth_sem_t *update_sem;
+empth_rwlock_t *update_lock;
 time_t update_time;
 
 static void update_wait(void *unused);
@@ -61,9 +62,9 @@ update_sched(void *unused)
     time_t now, delta;
 
     update_sem = empth_sem_create("Update", 0);
+    update_lock = empth_rwlock_create("Update");
     empth_create(PP_SCHED, update_wait, (50 * 1024), 0, "UpdateWait",
 		 "Waits until players idle", 0);
-    time(&now);
     if (s_p_etu <= 0) {
 	logerror("bad value for s_p_etu (%d)", s_p_etu);
 	s_p_etu = 2 * 60;
@@ -116,15 +117,12 @@ static void
 update_wait(void *unused)
 {
     struct player *p;
-    int running;
-    time_t now;
     int stacksize;
     struct player *dp;
 
     while (1) {
 	empth_sem_wait(update_sem);
 	update_pending = 1;
-	running = 0;
 	for (p = player_next(0); p != 0; p = player_next(p)) {
 	    if (p->state != PS_PLAYING)
 		continue;
@@ -132,17 +130,13 @@ update_wait(void *unused)
 		pr_flash(p, "Update aborting command\n");
 		p->aborted = 1;
 		empth_wakeup(p->proc);
-		running++;
 	    }
 	}
-	time(&now);
+	empth_rwlock_wrlock(update_lock);
-	if (running) {
-	    /* sleep a few, wait for aborts to take effect */
-	    empth_sleep(now + 2);
-	}
 	if (*pre_update_hook) {
 	    if (run_hook(pre_update_hook, "pre-update")) {
 		update_pending = 0;
+		empth_rwlock_unlock(update_lock);
 		continue;
 	    }
 	}
@@ -154,6 +148,7 @@ update_wait(void *unused)
 	if (!dp) {
 	    logerror("can't create dummy player for update");
 	    update_pending = 0;
+	    empth_rwlock_unlock(update_lock);
 	    continue;
 	}
 	stacksize = 100000 +
@@ -162,6 +157,11 @@ update_wait(void *unused)
 
 	empth_create(PP_UPDATE, update_main, stacksize, 0,
 		     "UpdateRun", "Updates the world", dp);
+
+	while (update_pending)
+	    empth_yield();	/* FIXME cheesy! */
+	update_pending = 0;
+	empth_rwlock_unlock(update_lock);
     }
     /*NOTREACHED*/
 }