[src/trunk]: src/sys/kern Move forward read pointer to the next line in the b...

[msaitoh <msaitoh%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/15d60069d4cf
branches:  trunk
changeset: 329492:15d60069d4cf
user:      msaitoh <msaitoh%NetBSD.org@localhost>
date:      Tue May 27 05:14:02 2014 +0000

description:
Move forward read pointer to the next line in the buffer
to prevent corrupting the most old line.

diffstat:

 sys/kern/subr_log.c |  26 ++++++++++++++++++++++----
 1 files changed, 22 insertions(+), 4 deletions(-)

diffs (47 lines):

diff -r 2dc10d427171 -r 15d60069d4cf sys/kern/subr_log.c
--- a/sys/kern/subr_log.c       Tue May 27 04:18:00 2014 +0000
+++ b/sys/kern/subr_log.c       Tue May 27 05:14:02 2014 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: subr_log.c,v 1.51 2014/03/16 05:20:30 dholland Exp $   */
+/*     $NetBSD: subr_log.c,v 1.52 2014/05/27 05:14:02 msaitoh Exp $    */
 
 /*-
  * Copyright (c) 2007, 2008 The NetBSD Foundation, Inc.
@@ -65,7 +65,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: subr_log.c,v 1.51 2014/03/16 05:20:30 dholland Exp $");
+__KERNEL_RCSID(0, "$NetBSD: subr_log.c,v 1.52 2014/05/27 05:14:02 msaitoh Exp $");
 
 #include <sys/param.h>
 #include <sys/systm.h>
@@ -387,8 +387,26 @@
                                mbp->msg_bufx = 0;
                        /* If the buffer is full, keep the most recent data. */
                        if (mbp->msg_bufr == mbp->msg_bufx) {
-                                if (++mbp->msg_bufr >= mbp->msg_bufs)
-                                       mbp->msg_bufr = 0;
+                               char c0;
+                               int i;
+
+                               /*
+                                * Move forward read pointer to the next line
+                                * in the buffer.  Note that the buffer is
+                                * a ring buffer so we should reset msg_bufr
+                                * to 0 when msg_bufr exceeds msg_bufs.
+                                *
+                                * To prevent to loop forever, give up if we
+                                * cannot find a newline in mbp->msg_bufs
+                                * characters (the max size of the buffer).
+                                */
+                               for (i = 0; i < mbp->msg_bufs; i++) {
+                                       c0 = mbp->msg_bufc[mbp->msg_bufr];
+                                       if (++mbp->msg_bufr >= mbp->msg_bufs)
+                                               mbp->msg_bufr = 0;
+                                       if (c0 == '\n')
+                                               break;
+                               }
                        }
                }
        }