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Fix race condition in start_input

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This commit is contained in:
clydebarrow
2025-10-26 10:05:44 +10:00
parent 28ee05b1a3
commit c3606a9229
1 changed files with 7 additions and 2 deletions
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9
esphome/components/usb_uart/usb_uart.cpp
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@@ -214,7 +214,7 @@ void USBUartComponent::dump_config() {
}
}
void USBUartComponent::start_input(USBUartChannel *channel) {
if (!channel->initialised_.load() || channel->input_started_.load())
if (!channel->initialised_.load())
return;
// THREAD CONTEXT: Called from both USB task and main loop threads
// - USB task: Immediate restart after successful transfer for continuous data flow
@@ -226,6 +226,12 @@ void USBUartComponent::start_input(USBUartChannel *channel) {
//
// The underlying transfer_in() uses lock-free atomic allocation from the
// TransferRequest pool, making this multi-threaded access safe
// if already started, don't restart. A spurious failure in compare_exchange_weak
// is not a problem, as it will be retried on the next read_array()
auto started = false;
if (!channel->input_started_.compare_exchange_weak(started, true))
return;
const auto *ep = channel->cdc_dev_.in_ep;
// CALLBACK CONTEXT: This lambda is executed in USB task via transfer_callback
auto callback = [this, channel](const usb_host::TransferStatus &status) {
@@ -263,7 +269,6 @@ void USBUartComponent::start_input(USBUartChannel *channel) {
channel->input_started_.store(false);
this->start_input(channel);
};
channel->input_started_.store(true);
if (!this->transfer_in(ep->bEndpointAddress, callback, ep->wMaxPacketSize)) {
channel->input_started_.store(false);
}