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From 9cf6c1d80c2f159dbb69967fbe934bf6de73c9e8 Mon Sep 17 00:00:00 2001
From: Max Krummenacher <max.krummenacher@toradex.com>
Date: Tue, 5 Aug 2025 09:35:06 +0200
Subject: [PATCH 2/2] linux-serial-test.c: fix potential hang in while loop
process_read_data() assumes that we can always wait for reception
of 1024 chars. However that is not true if one sets the number of
chars with the '-w' cmdline parameter or chars are lost. Maybe there
are other reasons.
Replace the magic number of 1024 by calculating the number of expected
chars from _cl_tx_bytes.
Brake a possible infinite while loop by adding a timeout to the loop
calculated from the expected chars times chartime.
Upstream-Status: Submitted [https://github.com/cbrake/linux-serial-test/pull/61/]
Fixes: 7fd1057f8a95 ("Add loop to read all data in rcv buffer")
Signed-off-by: Max Krummenacher <max.krummenacher@toradex.com>
Signed-off-by: Emanuele Ghidoli <emanuele.ghidoli@toradex.com>
---
linux-serial-test.c | 14 ++++++++++++--
1 file changed, 12 insertions(+), 2 deletions(-)
diff --git a/linux-serial-test.c b/linux-serial-test.c
index c2c8882d601b..294f53882570 100644
--- a/linux-serial-test.c
+++ b/linux-serial-test.c
@@ -543,8 +543,13 @@ static unsigned char next_count_value(unsigned char c)
static void process_read_data(void)
{
unsigned char rb[1024];
+ int loopcounter = 0;
int actual_read_count = 0;
- while (actual_read_count < 1024) {
+ int expected_read_count = _cl_tx_bytes == 0 ? 1024 : _cl_tx_bytes;
+ /* time for one char at current baudrate in us */
+ int chartime = 1000000 * (8 + _cl_parity + 1 + _cl_2_stop_bit) / _cl_baud;
+
+ while (actual_read_count < expected_read_count) {
int c = read(_fd, &rb, sizeof(rb));
if (c > 0) {
if (_cl_rx_dump) {
@@ -577,7 +582,12 @@ static void process_read_data(void)
if (errno != EAGAIN) {
perror("read failed");
}
- continue; // Retry the read
+
+ if (loopcounter++ < expected_read_count) {
+ usleep(chartime);
+ continue; // Retry the read
+ }
+ break;
} else {
break;
}
--
2.43.0
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