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[usb_host] Fix double-free crash with lock-free atomic pool allocation (#10926)

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This commit is contained in:
J. Nick Koston
2025-09-28 23:48:51 -05:00
committed by GitHub
parent a56d044d98
commit 0246a8eb1d
3 changed files with 117 additions and 28 deletions
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13
esphome/components/usb_uart/usb_uart.cpp
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@@ -216,9 +216,16 @@ void USBUartComponent::dump_config() {
void USBUartComponent::start_input(USBUartChannel *channel) {
if (!channel->initialised_.load() || channel->input_started_.load())
return;
// Note: This function is called from both USB task and main loop, so we cannot
// directly check ring buffer space here. Backpressure is handled by the chunk pool:
// when exhausted, USB input stops until chunks are freed by the main loop
// THREAD CONTEXT: Called from both USB task and main loop threads
// - USB task: Immediate restart after successful transfer for continuous data flow
// - Main loop: Controlled restart after consuming data (backpressure mechanism)
//
// This dual-thread access is intentional for performance:
// - USB task restarts avoid context switch delays for high-speed data
// - Main loop restarts provide flow control when buffers are full
//
// The underlying transfer_in() uses lock-free atomic allocation from the
// TransferRequest pool, making this multi-threaded access safe
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) {