sendmsg(3) may block, so retry

[mandoc.git] / catman.c

diff --git a/catman.c b/catman.c
index 5ecef67ed3371b9f4bd1eec382d6c2bd0ccd0b5d..6c9276d4aea2fdaaa2d4cbdc36a714003bcf132a 100644 (file)
--- a/catman.c
+++ b/catman.c
@@ -1,4 +1,4 @@
-/*     $Id: catman.c,v 1.14 2017/02/06 19:02:37 schwarze Exp $ */
+/*     $Id: catman.c,v 1.15 2017/02/08 14:50:53 schwarze Exp $ */
 /*
  * Copyright (c) 2017 Michael Stapelberg <stapelberg@debian.org>
  * Copyright (c) 2017 Ingo Schwarze <schwarze@openbsd.org>
@@ -34,6 +34,7 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <time.h>
 #include <unistd.h>
 
 int     process_manpage(int, int, const char *);
@@ -62,6 +63,7 @@ run_mandocd(int sockfd, const char *outtype, const char* defos)
 ssize_t
 sock_fd_write(int fd, int fd0, int fd1, int fd2)
 {
+       const struct timespec timeout = { 0, 10000000 };  /* 0.01 s */
        struct msghdr    msg;
        struct iovec     iov;
        union {
@@ -70,6 +72,7 @@ sock_fd_write(int fd, int fd0, int fd1, int fd2)
        } cmsgu;
        struct cmsghdr  *cmsg;
        int             *walk;
+       ssize_t          sz;
        unsigned char    dummy[1] = {'\0'};
 
        iov.iov_base = dummy;
@@ -93,7 +96,21 @@ sock_fd_write(int fd, int fd0, int fd1, int fd2)
        *(walk++) = fd1;
        *(walk++) = fd2;
 
-       return sendmsg(fd, &msg, 0);
+       /*
+        * It appears that on some systems, sendmsg(3)
+        * may return EAGAIN even in blocking mode.
+        * Seen for example on Oracle Solaris 11.2.
+        * The sleeping time was chosen by experimentation,
+        * to neither cause more than a handful of retries
+        * in normal operation nor unnecessary delays.
+        */
+       for (;;) {
+               if ((sz = sendmsg(fd, &msg, 0)) != -1 ||
+                   errno != EAGAIN)
+                       break;
+               nanosleep(&timeout, NULL);
+       }
+       return sz;
 }
 
 int