0.36.0 gdbserver generates "USB Error: [Errno 10060] Operation timed out"

Hello,

I am using pyocd to host a GDB server and encountering an issue where the GDB server fails to open a debug session after flashing a firmware.

Here's the sequence of steps:

1. I start the GDB server with the command:
   pyocd gdbserver -r --allow-remote --persist -S --verbose
   The server initialization seems to work fine.

2. Connecting with a GDB client at this point works as expected.

3. However, if I flash a Zephyr firmware before debugging using the command:
   west flash -r pyocd --dev-id remote:<ip-addr>:5555
   The output indicates successful flashing:

0006995 I Semihost server started on port 4444 (core 0) [server]
0007585 I GDB server started on port 3333 (core 0) [gdbserver]
0022919 I Client kubernetes.docker.internal (port 54076) connected to probe 001F002D3137510939383538 [tcp_probe_server]
0022922 D actual SWD frequency is 1000 kHz [stlink]
0022961 D creating memif for AP#0 (handle 0) [tcp_probe_server]
0022968 D creating memif for AP#1 (handle 1) [tcp_probe_server]
0022975 D creating memif for AP#2 (handle 2) [tcp_probe_server]
0024283 D empty request, closing connection [tcp_probe_server]
0024283 I Client kubernetes.docker.internal (port 54076) disconnected from probe 001F002D3137510939383538 [tcp_probe_server]

4. When attempting to connect a debug session after flashing, I receive the following error message, indicating a timeout issue:

0165915 D Starting GDB server packet I/O thread [packet_io]
0165915 D halting core 0 [cortex_m]
0166921 E Unexpected exception: USB Error: [Errno 10060] Operation timed out [gdbserver]
Traceback (most recent call last):
  File "C:\Users\XXX\AppData\Local\Programs\Python\Python312\Lib\site-packages\pyocd\probe\stlink\usb.py", line 249, in transfer
    count = self._ep_out.write(writeData, timeout)
            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\XXX\AppData\Local\Programs\Python\Python312\Lib\site-packages\usb\core.py", line 408, in write
    return self.device.write(self, data, timeout)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\XXX\AppData\Local\Programs\Python\Python312\Lib\site-packages\usb\core.py", line 989, in write
    return fn(
           ^^^
  File "C:\Users\XXX\AppData\Local\Programs\Python\Python312\Lib\site-packages\usb\backend\libusb1.py", line 837, in bulk_write
    return self.__write(self.lib.libusb_bulk_transfer,
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\XXX\AppData\Local\Programs\Python\Python312\Lib\site-packages\usb\backend\libusb1.py", line 938, in __write
    _check(retval)
  File "C:\Users\XXX\AppData\Local\Programs\Python\Python312\Lib\site-packages\usb\backend\libusb1.py", line 602, in _check
    raise USBTimeoutError(_strerror(ret), ret, _libusb_errno[ret])
usb.core.USBTimeoutError: [Errno 10060] Operation timed out

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "C:\Users\XXX\AppData\Local\Programs\Python\Python312\Lib\site-packages\pyocd\gdbserver\gdbserver.py", line 336, in run
    self.target.halt()
  File "C:\Users\XXX\AppData\Local\Programs\Python\Python312\Lib\site-packages\pyocd\coresight\cortex_m.py", line 638, in halt
    self.write_memory(CortexM.DHCSR, CortexM.DBGKEY | CortexM.C_DEBUGEN | CortexM.C_HALT)
  File "C:\Users\XXX\AppData\Local\Programs\Python\Python312\Lib\site-packages\pyocd\coresight\cortex_m.py", line 579, in write_memory
    self.ap.write_memory(addr, data, transfer_size)
  File "C:\Users\XXX\AppData\Local\Programs\Python\Python312\Lib\site-packages\pyocd\utility\concurrency.py", line 29, in _locking
    return func(self, *args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\XXX\AppData\Local\Programs\Python\Python312\Lib\site-packages\pyocd\coresight\ap.py", line 1227, in _accelerated_write_memory
    self._accelerated_memory_interface.write_memory(addr, data, transfer_size,
  File "C:\Users\XXX\AppData\Local\Programs\Python\Python312\Lib\site-packages\pyocd\probe\stlink_probe.py", line 292, in write_memory
    self._link.write_mem32(addr, conversion.u32le_list_to_byte_list([data]), self._apsel, csw)
  File "C:\Users\XXX\AppData\Local\Programs\Python\Python312\Lib\site-packages\pyocd\probe\stlink\stlink.py", line 477, in write_mem32
    self._write_mem(addr, data, Commands.JTAG_WRITEMEM_32BIT, self.MAXIMUM_TRANSFER_SIZE, apsel, csw)
  File "C:\Users\XXX\AppData\Local\Programs\Python\Python312\Lib\site-packages\pyocd\probe\stlink\stlink.py", line 446, in _write_mem
    self._device.transfer(cmd, writeData=thisTransferData)
  File "C:\Users\XXX\AppData\Local\Programs\Python\Python312\Lib\site-packages\pyocd\probe\stlink\usb.py", line 267, in transfer
    raise exceptions.ProbeError("USB Error: %s" % exc) from exc
pyocd.core.exceptions.ProbeError: USB Error: [Errno 10060] Operation timed out
Exception in thread gdb-packet-thread-port3333:
Traceback (most recent call last):
  File "C:\Users\XXX\AppData\Local\Programs\Python\Python312\Lib\threading.py", line 1052, in _bootstrap_inner
    self.run()
  File "C:\Users\XXX\AppData\Local\Programs\Python\Python312\Lib\site-packages\pyocd\gdbserver\packet_io.py", line 111, in run
    data = self._abstract_socket.read()
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\XXX\AppData\Local\Programs\Python\Python312\Lib\site-packages\pyocd\utility\sockets.py", line 55, in read
    return self.conn.recv(packet_size)
           ^^^^^^^^^^^^^^
AttributeError: 'NoneType' object has no attribute 'recv'

To reproduce the issue, you can perform a fresh install of the following software versions:

• pyocd version 0.36.0
• libusb.dll version 1.0.26 (copied to the Python folder)
• STLINKV3 with Firmware version V3J13M4 (recommended by en.stsw-link007-v3-13-4)
• Windows OS 64Bit

I appreciate your assistance in addressing this issue.

Best regards.

Reproduce the reported sequence with pyocd 0.36.0, west flash, an STLINKV3, and Windows. Read pyocd/probe/stlink/usb.py around transfer(), then follow the gdbserver.py run() path and the related packet_io failure. Done means a debug session can start after flashing without the USB timeout or resulting connection exception.