script: fix a rare deadlock after child termination

diff --git a/term-utils/script.c b/term-utils/script.c
index e5d239c9b8540a9fbb0936abaee727599896ed01..47bb186bf8354e7d9f762ca5b08144dc8394233f 100644 (file)
--- a/term-utils/script.c
+++ b/term-utils/script.c
@@ -36,6 +36,9 @@
  * - added Native Language Support
  *
  * 2000-07-30 Per Andreas Buer <per@linpro.no> - added "q"-option
+ *
+ * 2014-05-30 Csaba Kos <csaba.kos@gmail.com>
+ * - fixed a rare deadlock after child termination
  */
 
 /*
@@ -114,6 +117,8 @@ int tflg = 0;
 int    forceflg = 0;
 int    isterm;
 
+sigset_t block_mask, unblock_mask;
+
 int die;
 int resized;
 
@@ -162,7 +167,6 @@ usage(FILE *out)
 
 int
 main(int argc, char **argv) {
-       sigset_t block_mask, unblock_mask;
        struct sigaction sa;
        int ch;
 
@@ -306,6 +310,7 @@ doinput(void) {
        int errsv = 0;
        ssize_t cc = 0;
        char ibuf[BUFSIZ];
+       fd_set readfds;
 
        /* close things irrelevant for this process */
        if (fscript)
@@ -314,14 +319,27 @@ doinput(void) {
                fclose(timingfd);
        fscript = timingfd = NULL;
 
+       FD_ZERO(&readfds);
+
+       /* block SIGCHLD */
+       sigprocmask(SIG_SETMASK, &block_mask, &unblock_mask);
+
        while (die == 0) {
-               if ((cc = read(STDIN_FILENO, ibuf, BUFSIZ)) > 0) {
-                       if (write_all(master, ibuf, cc)) {
-                               warn (_("write failed"));
-                               fail();
+               FD_SET(STDIN_FILENO, &readfds);
+
+               /* wait for input or signal (including SIGCHLD) */
+               if ((cc = pselect(STDIN_FILENO + 1, &readfds, NULL, NULL, NULL,
+                       &unblock_mask)) > 0) {
+
+                       if ((cc = read(STDIN_FILENO, ibuf, BUFSIZ)) > 0) {
+                               if (write_all(master, ibuf, cc)) {
+                                       warn (_("write failed"));
+                                       fail();
+                               }
                        }
                }
-               else if (cc < 0 && errno == EINTR && resized)
+
+               if (cc < 0 && errno == EINTR && resized)
                {
                        /* transmit window change information to the child */
                        if (isterm) {
@@ -330,12 +348,15 @@ doinput(void) {
                        }
                        resized = 0;
 
-               } else {
+               } else if (cc <= 0) {
                        errsv = errno;
                        break;
                }
        }
 
+       /* unblock SIGCHLD */
+       sigprocmask(SIG_SETMASK, &unblock_mask, NULL);
+
        /* To be sure that we don't miss any data */
        wait_for_empty_fd(slave);
        wait_for_empty_fd(master);
@@ -404,6 +425,7 @@ dooutput(void) {
        struct timeval tv;
        double oldtime=time(NULL), newtime;
        int errsv = 0;
+       fd_set readfds;
 
        close(STDIN_FILENO);
 #ifdef HAVE_LIBUTIL
@@ -416,6 +438,8 @@ dooutput(void) {
        my_strftime(obuf, sizeof obuf, "%c\n", localtime(&tvec));
        fprintf(fscript, _("Script started on %s"), obuf);
 
+       FD_ZERO(&readfds);
+
        do {
                if (die || errsv == EINTR) {
                        struct pollfd fds[] = {{ .fd = master, .events = POLLIN }};
@@ -423,10 +447,23 @@ dooutput(void) {
                                break;
                }
 
+               /* block SIGCHLD */
+               sigprocmask(SIG_SETMASK, &block_mask, &unblock_mask);
+
+               FD_SET(master, &readfds);
                errno = 0;
-               cc = read(master, obuf, sizeof (obuf));
+
+               /* wait for input or signal (including SIGCHLD) */
+               if ((cc = pselect(master+1, &readfds, NULL, NULL, NULL,
+                       &unblock_mask)) > 0) {
+
+                       cc = read(master, obuf, sizeof (obuf));
+               }
                errsv = errno;
 
+               /* unblock SIGCHLD */
+               sigprocmask(SIG_SETMASK, &unblock_mask, NULL);
+
                if (tflg)
                        gettimeofday(&tv, NULL);