logtee: time out after a period of no output

Travis cuts us short after 10 minutes of slience, giving us no chance to puke
out the output. Be faster.

fedora-test.sh

@@ -53,7 +53,7 @@ else
 
     cd test
 
-    time sudo make \
+    time sudo LOGTEE_TIMEOUT_MS=590000 make \
          KVERSION=$(rpm -qa kernel --qf '%{VERSION}-%{RELEASE}.%{ARCH}\n' | sort -rn | head -1) \
          TEST_RUN_ID=$RUN_ID \
          ${TESTS:+TESTS="$TESTS"} \

logtee.c

@@ -1,5 +1,6 @@
 #define _GNU_SOURCE
 #include <fcntl.h>
+#include <poll.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <unistd.h>
@@ -13,13 +14,26 @@ main(int argc, char *argv[])
 {
 	int fd;
 	int len, slen;
+	int ret;
+	int timeout;
+	char *timeout_env;
+	struct pollfd fds[] = {{
+		.fd = STDIN_FILENO,
+		.events = POLLIN | POLLERR,
+	}};
+
+	timeout_env = getenv("LOGTEE_TIMEOUT_MS");
+	if (timeout_env)
+		timeout = atoi(timeout_env);
+	else
+		timeout = -1;
 
 	if (argc != 2) {
 		fprintf(stderr, "Usage: %s <file>\n", argv[0]);
 		exit(EXIT_FAILURE);
 	}
 
-	fd = open(argv[1], O_WRONLY | O_CREAT | O_TRUNC, 0644);
+	fd = open(argv[1], O_WRONLY | O_CREAT | O_TRUNC | O_NONBLOCK, 0644);
 	if (fd == -1) {
 		perror("open");
 		exit(EXIT_FAILURE);
@@ -30,8 +44,13 @@ main(int argc, char *argv[])
 	slen = 0;
 
 	do {
+		ret = poll (fds, sizeof(fds) / sizeof(fds[0]), timeout);
+		if (ret == 0) {
+			fprintf (stderr, "Timed out after %d milliseconds of no output.\n", timeout);
+			exit(EXIT_FAILURE);
+		}
 		len = splice(STDIN_FILENO, NULL, fd, NULL,
-			     BUFLEN, SPLICE_F_MOVE);
+			     BUFLEN, SPLICE_F_MOVE | SPLICE_F_NONBLOCK);
 
 		if (len < 0) {
 			if (errno == EAGAIN)
@@ -51,4 +70,4 @@ main(int argc, char *argv[])
 	close(fd);
 	fprintf(stderr, "\n");
 	exit(EXIT_SUCCESS);
-}
+}