HAL_SITL: fixed unbuffered UART writes in SITL

this was causing PPP to slow down by about 1000x due to duplicate writes
tridge · Dec 30, 2023 · d128d84 · d128d84
1 parent 84b8f3a
commit d128d84
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diff --git a/libraries/AP_HAL_SITL/UARTDriver.cpp b/libraries/AP_HAL_SITL/UARTDriver.cpp
@@ -799,6 +799,7 @@ uint16_t UARTDriver::read_from_async_csv(uint8_t *buffer, uint16_t space)
 
 void UARTDriver::handle_writing_from_writebuffer_to_device()
 {
+    WITH_SEMAPHORE(write_mtx);
     if (!_connected) {
         _check_reconnect();
         return;

diff --git a/libraries/AP_HAL_SITL/UARTDriver.h b/libraries/AP_HAL_SITL/UARTDriver.h
@@ -109,6 +109,8 @@ class HALSITL::UARTDriver : public AP_HAL::UARTDriver {
     uint32_t last_read_tick_us;
     uint32_t last_write_tick_us;
 
+    HAL_Semaphore write_mtx;
+
     SITL::SerialDevice *_sim_serial_device;
 
     struct {