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HAL_ChibiOS: replace volatile bools with mutexes

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this replaces the two booleans used to mediate TX and RX buffer
protection with mutexes.

The booleans were a hangover from the very early HAL_ChibiOS code, and
can lead to a deadlock. The sequence is as follows:

 - a very high CAN bus bandwidth usage, triggered by MissionPlanner
   requesting CAN_FORWARD on a CAN serial port. That causes a
   "infinite" number of CAN_FRAME messages which saturates the bus,
   and leads to the DroneCAN thread looping with no pause

 - a serial port configured as GPS type AUTO, auto-probing for a GPS
   that isn't there. This calls begin() periodically

 - the UART TX thread assocated with that UART not making progress as
   the TX thread priority is below the DroneCAN thread priority

 - this causes the begin() in main thread waiting for _in_tx_timer to
   loop forever, which triggers a watchdog
This commit is contained in:
Andrew Tridgell 2024-09-24 20:49:19 +10:00
parent 5ab9cda206
commit 52169f25da
2 changed files with 12 additions and 22 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

26
libraries/AP_HAL_ChibiOS/UARTDriver.cpp
View File

@ -295,9 +295,7 @@ void UARTDriver::_begin(uint32_t b, uint16_t rxS, uint16_t txS)
thrashing of the heap once we are up. The ttyACM0 driver may not
connect for some time after boot
*/
while (_in_rx_timer) {
hal.scheduler->delay(1);
}
WITH_SEMAPHORE(rx_sem);
if (rxS != _readbuf.get_size()) {
_rx_initialised = false;
_readbuf.set_size_best(rxS);
@ -359,9 +357,7 @@ void UARTDriver::_begin(uint32_t b, uint16_t rxS, uint16_t txS)
/*
allocate the write buffer
*/
while (_in_tx_timer) {
hal.scheduler->delay(1);
}
WITH_SEMAPHORE(tx_sem);
if (txS != _writebuf.get_size()) {
_tx_initialised = false;
_writebuf.set_size_best(txS);
@ -640,9 +636,9 @@ __RAMFUNC__ void UARTDriver::rxbuff_full_irq(void* self, uint32_t flags)
void UARTDriver::_end()
{
while (_in_rx_timer) hal.scheduler->delay(1);
WITH_SEMAPHORE(rx_sem);
WITH_SEMAPHORE(tx_sem);
_rx_initialised = false;
while (_in_tx_timer) hal.scheduler->delay(1);
_tx_initialised = false;
if (sdef.is_usb) {
@ -1112,7 +1108,7 @@ void UARTDriver::_rx_timer_tick(void)
return;
}
_in_rx_timer = true;
WITH_SEMAPHORE(rx_sem);
#if HAL_UART_STATS_ENABLED && CH_CFG_USE_EVENTS == TRUE
if (!sdef.is_usb) {
@ -1165,7 +1161,6 @@ void UARTDriver::_rx_timer_tick(void)
if (sdef.is_usb) {
#ifdef HAVE_USB_SERIAL
if (((SerialUSBDriver*)sdef.serial)->config->usbp->state != USB_ACTIVE) {
_in_rx_timer = false;
return;
}
#endif
@ -1189,7 +1184,6 @@ void UARTDriver::_rx_timer_tick(void)
fwd_otg2_serial();
}
#endif
_in_rx_timer = false;
}
// forward data from a serial port to the USB
@ -1308,9 +1302,8 @@ void UARTDriver::_tx_timer_tick(void)
return;
}
_in_tx_timer = true;
if (hd_tx_active) {
WITH_SEMAPHORE(tx_sem);
hd_tx_active &= ~chEvtGetAndClearFlags(&hd_listener);
if (!hd_tx_active) {
/*
@ -1328,7 +1321,6 @@ void UARTDriver::_tx_timer_tick(void)
if (sdef.is_usb) {
#ifdef HAVE_USB_SERIAL
if (((SerialUSBDriver*)sdef.serial)->config->usbp->state != USB_ACTIVE) {
_in_tx_timer = false;
return;
}
#endif
@ -1341,18 +1333,16 @@ void UARTDriver::_tx_timer_tick(void)
// half duplex we do reads in the write thread
if (half_duplex) {
_in_rx_timer = true;
WITH_SEMAPHORE(rx_sem);
read_bytes_NODMA();
if (_wait.thread_ctx && _readbuf.available() >= _wait.n) {
chEvtSignal(_wait.thread_ctx, EVT_DATA);
}
_in_rx_timer = false;
}
// now do the write
WITH_SEMAPHORE(tx_sem);
write_pending_bytes();
_in_tx_timer = false;
}
/*

4
libraries/AP_HAL_ChibiOS/UARTDriver.h
View File

@ -196,8 +196,8 @@ private:
const stm32_dma_stream_t* rxdma;
const stm32_dma_stream_t* txdma;
#endif
volatile bool _in_rx_timer;
volatile bool _in_tx_timer;
HAL_Semaphore tx_sem;
HAL_Semaphore rx_sem;
volatile bool _rx_initialised;
volatile bool _tx_initialised;
volatile bool _device_initialised;