From 791de408857258f448c7462d7b296a3f526f2c5d Mon Sep 17 00:00:00 2001
From: Scott Lahteine <thinkyhead@users.noreply.github.com>
Date: Sun, 27 Nov 2022 23:23:00 -0600
Subject: [PATCH] =?UTF-8?q?=F0=9F=90=9B=20Fix=20G-code=20resend=20race=20c?=
=?UTF-8?q?ondition?=
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As pointed out in #24972 by @silycr, but simplified.
---
Marlin/src/gcode/queue.cpp | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/Marlin/src/gcode/queue.cpp b/Marlin/src/gcode/queue.cpp
index a390a46d8e3..c951fc63336 100644
--- a/Marlin/src/gcode/queue.cpp
+++ b/Marlin/src/gcode/queue.cpp
@@ -469,8 +469,11 @@ void GCodeQueue::get_serial_commands() {
const long gcode_N = strtol(npos + 1, nullptr, 10);
+ // The line number must be in the correct sequence.
if (gcode_N != serial.last_N + 1 && !M110) {
- // In case of error on a serial port, don't prevent other serial port from making progress
+ // A request-for-resend line was already in transit so we got two - oops!
+ if (WITHIN(gcode_N, serial.last_N - 1, serial.last_N)) continue;
+ // A corrupted line or too high, indicating a lost line
gcode_line_error(F(STR_ERR_LINE_NO), p);
break;
}
@@ -480,13 +483,11 @@ void GCodeQueue::get_serial_commands() {
uint8_t checksum = 0, count = uint8_t(apos - command);
while (count) checksum ^= command[--count];
if (strtol(apos + 1, nullptr, 10) != checksum) {
- // In case of error on a serial port, don't prevent other serial port from making progress
gcode_line_error(F(STR_ERR_CHECKSUM_MISMATCH), p);
break;
}
}
else {
- // In case of error on a serial port, don't prevent other serial port from making progress
gcode_line_error(F(STR_ERR_NO_CHECKSUM), p);
break;
}