⚠️ Bluetooth: btnxpuart: Resolve TX timeout error in power save stress test (Linux Linux)

Description

In the Linux kernel, the following vulnerability has been resolved: Bluetooth: btnxpuart: Resolve TX timeout error in power save stress test This fixes the tx timeout issue seen while running a stress test on btnxpuart for couple of hours, such that the interval between two HCI commands coincide with the power save timeout value of 2 seconds. Test procedure using bash script: <load btnxpuart.ko> hciconfig hci0 up //Enable Power Save feature hcitool -i hci0 cmd 3f 23 02 00 00 while (true) do hciconfig hci0 leadv sleep 2 hciconfig hci0 noleadv sleep 2 done Error log, after adding few more debug prints: Bluetooth: btnxpuart_queue_skb(): 01 0A 20 01 00 Bluetooth: hci0: Set UART break: on, status=0 Bluetooth: hci0: btnxpuart_tx_wakeup() tx_work scheduled Bluetooth: hci0: btnxpuart_tx_work() dequeue: 01 0A 20 01 00 Can't set advertise mode on hci0: Connection timed out (110) Bluetooth: hci0: command 0x200a tx timeout When the power save mechanism turns on UART break, and btnxpuart_tx_work() is scheduled simultaneously, psdata->ps_state is read as PS_STATE_AWAKE, which prevents the psdata->work from being scheduled, which is responsible to turn OFF UART break. This issue is fixed by adding a ps_lock mutex around UART break on/off as well as around ps_state read/write. btnxpuart_tx_wakeup() will now read updated ps_state value. If ps_state is PS_STATE_SLEEP, it will first schedule psdata->work, and then it will reschedule itself once UART break has been turned off and ps_state is PS_STATE_AWAKE. Tested above script for 50,000 iterations and TX timeout error was not observed anymore.