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fix mavlink: add mutex for mavlink shell (#25082)

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There was a race condition when closing the shell:
- the main thread checks if _mavlink_shell is not nullptr (which is true)
- the receiver thread closes the shell, which clears _mavlink_shell
- the main thread continues with _mavlink_shell->available()
This commit is contained in:
Beat Küng
2025-06-19 23:03:01 +02:00
committed by GitHub
parent 873aa89022
commit afbaa71bfc
3 changed files with 37 additions and 15 deletions
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src/modules/mavlink/mavlink_main.cpp
+31 -15
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@@ -2236,6 +2236,7 @@ Mavlink::task_main(int argc, char *argv[])
return PX4_ERROR;
}
pthread_mutex_init(&_mavlink_shell_mutex, nullptr);
pthread_mutex_init(&_message_buffer_mutex, nullptr);
pthread_mutex_init(&_send_mutex, nullptr);
pthread_mutex_init(&_radio_status_mutex, nullptr);
@@ -2374,21 +2375,7 @@ Mavlink::task_main(int argc, char *argv[])
handleStatus();
handleCommands();
handleAndGetCurrentCommandAck();
/* check for shell output */
if (_mavlink_shell && _mavlink_shell->available() > 0) {
if (get_free_tx_buf() >= MAVLINK_MSG_ID_SERIAL_CONTROL_LEN + MAVLINK_NUM_NON_PAYLOAD_BYTES) {
mavlink_serial_control_t msg;
msg.baudrate = 0;
msg.flags = SERIAL_CONTROL_FLAG_REPLY;
msg.timeout = 0;
msg.device = SERIAL_CONTROL_DEV_SHELL;
msg.count = _mavlink_shell->read(msg.data, sizeof(msg.data));
msg.target_system = _mavlink_shell->targetSysid();
msg.target_component = _mavlink_shell->targetCompid();
mavlink_msg_serial_control_send_struct(get_channel(), &msg);
}
}
handleMavlinkShellOutput();
check_requested_subscriptions();
@@ -2521,6 +2508,7 @@ Mavlink::task_main(int argc, char *argv[])
_mavlink_ulog = nullptr;
}
pthread_mutex_destroy(&_mavlink_shell_mutex);
pthread_mutex_destroy(&_send_mutex);
pthread_mutex_destroy(&_radio_status_mutex);
pthread_mutex_destroy(&_message_buffer_mutex);
@@ -2563,6 +2551,34 @@ void Mavlink::handleStatus()
}
}
void Mavlink::handleMavlinkShellOutput()
{
if (_mavlink_shell) { // First do a fast check before taking the lock
mavlink_serial_control_t msg;
msg.count = 0;
{
const LockGuard lg{_mavlink_shell_mutex};
if (_mavlink_shell && _mavlink_shell->available() > 0) {
if (get_free_tx_buf() >= MAVLINK_MSG_ID_SERIAL_CONTROL_LEN + MAVLINK_NUM_NON_PAYLOAD_BYTES) {
msg.baudrate = 0;
msg.flags = SERIAL_CONTROL_FLAG_REPLY;
msg.timeout = 0;
msg.device = SERIAL_CONTROL_DEV_SHELL;
msg.count = _mavlink_shell->read(msg.data, sizeof(msg.data));
msg.target_system = _mavlink_shell->targetSysid();
msg.target_component = _mavlink_shell->targetCompid();
}
}
}
// Send message without lock
if (msg.count > 0) {
mavlink_msg_serial_control_send_struct(get_channel(), &msg);
}
}
}
void Mavlink::handleCommands()
{
if (_mode == MAVLINK_MODE_IRIDIUM) {