[Bug 1732] ntpd ties up CPU on disconnected USB refclock.

bk: 4d899de8GbChT1BxW-djmPvLC8kDHA

diff --git a/ChangeLog b/ChangeLog
index d16d7c34701e72cffcc60af2f866133b1ec86162..c4c67c65b4a4d414fb6c07ed03d6f1a1064069d6 100644 (file)
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,4 @@
+* [Bug 1732] ntpd ties up CPU on disconnected USB refclock.
 * Remove kernel line discipline driver code for clk and chu, deprecate
   related LDISC_ flags, and remove associated ntpd code to decode the
   timestamps, remove clktest line discipline test program.

diff --git a/ntpd/ntp_io.c b/ntpd/ntp_io.c
index 56be2bd1abd3286f7b31e612429c2b8e72467a74..d89e98587a9e6819b70866f4f753b303c3e198b1 100644 (file)
--- a/ntpd/ntp_io.c
+++ b/ntpd/ntp_io.c
@@ -3076,7 +3076,8 @@ read_refclock_packet(SOCKET fd, struct refclockio *rp, l_fp ts)
 {
        int i;
        int buflen;
-       register struct recvbuf *rb;
+       int saved_errno;
+       struct recvbuf *rb;
 
        rb = get_free_recv_buffer();
 
@@ -3095,13 +3096,15 @@ read_refclock_packet(SOCKET fd, struct refclockio *rp, l_fp ts)
             || rp->datalen > sizeof(rb->recv_space))
                ? sizeof(rb->recv_space)
                : rp->datalen;
-       buflen = read(fd, (char *)&rb->recv_space, (unsigned)i);
+       do {
+               buflen = read(fd, (char *)&rb->recv_space, (u_int)i);
+       } while (buflen < 0 && EINTR == errno);
 
-       if (buflen < 0) {
-               if (errno != EINTR && errno != EAGAIN)
-                       msyslog(LOG_ERR, "clock read fd %d: %m", fd);
+       if (buflen <= 0) {
+               saved_errno = errno;
                freerecvbuf(rb);
-               return (buflen);
+               errno = saved_errno;
+               return buflen;
        }
 
        /*
@@ -3330,6 +3333,9 @@ input_handler(
 #endif
        fd_set          fds;
        size_t          select_count;
+       struct refclockio *rp;
+       int             saved_errno;
+       const char *    clk;
        endpt *         ep;
 #ifdef HAS_ROUTING_SOCKET
        struct asyncio_reader *asyncio_reader;
@@ -3397,17 +3403,38 @@ input_handler(
         */
 
        if (refio != NULL) {
-               register struct refclockio *rp;
-
                for (rp = refio; rp != NULL; rp = rp->next) {
                        fd = rp->fd;
 
-                       if (FD_ISSET(fd, &fds))
+                       if (!FD_ISSET(fd, &fds))
+                               continue;
+                       ++select_count;
+                       buflen = read_refclock_packet(fd, rp, ts);
+                       /*
+                        * The first read must succeed after select()
+                        * indicates readability, or we've reached
+                        * a permanent EOF.  http://bugs.ntp.org/1732
+                        * reported ntpd munching CPU after a USB GPS
+                        * was unplugged because select was indicating
+                        * EOF but ntpd didn't remove the descriptor
+                        * from the activefds set.
+                        */
+                       if (buflen < 0 && EAGAIN != errno) {
+                               saved_errno = errno;
+                               clk = refnumtoa(&rp->srcclock->srcadr);
+                               errno = saved_errno;
+                               msyslog(LOG_ERR, "%s read: %m", clk);
+                               maintain_activefds(fd, TRUE);
+                       } else if (0 == buflen) {
+                               clk = refnumtoa(&rp->srcclock->srcadr);
+                               msyslog(LOG_ERR, "%s read EOF", clk);
+                               maintain_activefds(fd, TRUE);
+                       } else {
+                               /* drain any remaining refclock input */
                                do {
-                                       ++select_count;
-                                       buflen = read_refclock_packet(
-                                                       fd, rp, ts);
+                                       buflen = read_refclock_packet(fd, rp, ts);
                                } while (buflen > 0);
+                       }
                }
        }
 #endif /* REFCLOCK */