Fix occasional incorrectly delayed call-file execution.

Since the dir timestamp is available at one second resolution, we cannot
know if it was updated within the same second after we scanned it.
Therefore, we will force another scan if the dir was just modified.

* Changed to force another scan if the directory was just modified.

(closes issue ASTERISK-19081)
Reported by: Knut Bakke

Review: https://reviewboard.asterisk.org/r/1688/
........

Merged revisions 355056 from http://svn.asterisk.org/svn/asterisk/branches/1.8
........

Merged revisions 355057 from http://svn.asterisk.org/svn/asterisk/branches/10


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@355058 65c4cc65-6c06-0410-ace0-fbb531ad65f3

pbx/pbx_spool.c

@@ -761,14 +761,17 @@ static void *scan_thread(void *unused)
 	struct dirent *de;
 	char fn[256];
 	int res;
-	time_t last = 0, next = 0, now;
+	int force_poll = 1;
+	time_t last = 0;
+	time_t next = 0;
+	time_t now;
 	struct timespec ts = { .tv_sec = 1 };
 
 	while (!ast_fully_booted) {
 		nanosleep(&ts, NULL);
 	}
 
-	for(;;) {
+	for (;;) {
 		/* Wait a sec */
 		nanosleep(&ts, NULL);
 		time(&now);
@@ -779,34 +782,50 @@ static void *scan_thread(void *unused)
 		}
 
 		/* Make sure it is time for us to execute our check */
-		if ((st.st_mtime == last) && (next && (next > now)))
+		if (!force_poll && st.st_mtime == last && (!next || now < next)) {
+			/*
+			 * The directory timestamp did not change and any delayed
+			 * call-file is not ready to be executed.
+			 */
 			continue;
+		}
 
 #if 0
 		printf("atime: %ld, mtime: %ld, ctime: %ld\n", st.st_atime, st.st_mtime, st.st_ctime);
 		printf("Ooh, something changed / timeout\n");
 #endif
-		next = 0;
-		last = st.st_mtime;
 
 		if (!(dir = opendir(qdir))) {
 			ast_log(LOG_WARNING, "Unable to open directory %s: %s\n", qdir, strerror(errno));
 			continue;
 		}
 
+		/*
+		 * Since the dir timestamp is available at one second
+		 * resolution, we cannot know if it was updated within the same
+		 * second after we scanned it.  Therefore, we will force another
+		 * scan if the dir was just modified.
+		 */
+		force_poll = (st.st_mtime == now);
+
+		next = 0;
+		last = st.st_mtime;
 		while ((de = readdir(dir))) {
 			snprintf(fn, sizeof(fn), "%s/%s", qdir, de->d_name);
 			if (stat(fn, &st)) {
 				ast_log(LOG_WARNING, "Unable to stat %s: %s\n", fn, strerror(errno));
 				continue;
 			}
-			if (!S_ISREG(st.st_mode))
+			if (!S_ISREG(st.st_mode)) {
+				/* Not a regular file. */
 				continue;
+			}
 			if (st.st_mtime <= now) {
 				res = scan_service(fn, now);
 				if (res > 0) {
-					/* Update next service time */
-					if (!next || (res < next)) {
+					/* The call-file is delayed or to be retried later. */
+					if (!next || res < next) {
+						/* This delayed call file expires earlier. */
 						next = res;
 					}
 				} else if (res) {
@@ -816,9 +835,11 @@ static void *scan_thread(void *unused)
 					next = st.st_mtime;
 				}
 			} else {
-				/* Update "next" update if necessary */
-				if (!next || (st.st_mtime < next))
+				/* The file's timestamp is in the future. */
+				if (!next || st.st_mtime < next) {
+					/* This call-file's timestamp expires earlier. */
 					next = st.st_mtime;
+				}
 			}
 		}
 		closedir(dir);