Upstream Status: https://lists.gnu.org/archive/html/bug-hurd/2025-12/msg00043.html
From 2c9868cd8974e75a028349aa1ec9b1417f5d6617 Mon Sep 17 00:00:00 2001
From: Yelninei <yelninei@tutamail.com>
Date: Thu, 2 Oct 2025 16:20:00 +0000
Subject: [PATCH] kmsg: Don't truncate messages when overflowing.
Instead of discarding a character drop the first unread one.
---
device/kmsg.c | 21 +++++++++------------
1 file changed, 9 insertions(+), 12 deletions(-)
diff --git a/device/kmsg.c b/device/kmsg.c
index e5b518e6..bb72930d 100644
--- a/device/kmsg.c
+++ b/device/kmsg.c
@@ -217,7 +217,6 @@ void
kmsg_putchar (int c)
{
io_req_t ior;
- int offset;
spl_t s = -1;
/* XXX: cninit is not called before cnputc is used. So call kmsginit
@@ -230,22 +229,20 @@ kmsg_putchar (int c)
if (spl_init)
s = simple_lock_irq (&kmsg_lock);
- offset = kmsg_write_offset + 1;
- if (offset == KMSGBUFSIZE)
- offset = 0;
-
- if (offset == kmsg_read_offset)
- {
- /* Discard C. */
- if (spl_init)
- simple_unlock_irq (s, &kmsg_lock);
- return;
- }
kmsg_buffer[kmsg_write_offset++] = c;
if (kmsg_write_offset == KMSGBUFSIZE)
kmsg_write_offset = 0;
+ if(kmsg_write_offset == kmsg_read_offset)
+ {
+ /* Drop first unread char */
+ kmsg_read_offset++;
+ if (kmsg_read_offset == KMSGBUFSIZE)
+ kmsg_read_offset = 0;
+ }
+
+
while ((ior = (io_req_t) dequeue_head (&kmsg_read_queue)) != NULL)
iodone (ior);
--
2.52.0