[DX010] fix possible cpld race access issue

[qnos]

Why I did it

fix possible cpld race read issue between watchdog and reboot cause process

How I did it

Use fcntl.flock to limit parallel access to cpld sys file

How to verify it

It can be simulated and verified with following python script

import fcntl
import signal
import threading

exit_flag = False

def get_cpld_reg_value(getreg_path, register):
    file = open(getreg_path, 'w+')
    # Acquire an exclusive lock on the file
    fcntl.flock(file, fcntl.LOCK_EX)

    try:
        file.write(register + '\n')
        file.flush()

        # Seek to the beginning of the file
        file.seek(0)

        # Read the content of the file
        result = file.readline().strip()
    finally:
        # Release the lock and close the file
        fcntl.flock(file, fcntl.LOCK_UN)
        file.close()

    return result

def cpld_read(thread_num, cpld_reg, expect_val):
    while not exit_flag:
        val
= get_cpld_reg_value("/sys/devices/platform/dx010_cpld/getreg",
cpld_reg)
        #print(f"Thread {thread_num}: get cpld reg {cpld_reg}, value
{val}")
        if val != expect_val:
            print(f"Thread {thread_num}: get cpld reg {cpld_reg}, value
{val}, expect_val {expect_val}")

def signal_handler(sig, frame):
    global exit_flag
    print("Ctrl+C detected. Quitting...")
    exit_flag = True

if __name__ == '__main__':
    # Register the signal handler for Ctrl+C
    signal.signal(signal.SIGINT, signal_handler)

    t1 = threading.Thread(target=cpld_read, args=(1, '0x103', '0x11',))
    t2 = threading.Thread(target=cpld_read, args=(2, '0x141', '0x00',))
    t1.start()
    t2.start()
    t1.join()
    t2.join()

Which release branch to backport (provide reason below if selected)

• 201811
• 201911
• 202006
• 202012
• 202106
• 202111
• 202205
• 202211

Tested branch (Please provide the tested image version)

Description for the changelog

Link to config_db schema for YANG module changes

A picture of a cute animal (not mandatory but encouraged)

[prgeor]

@yxieca @lguohan please help merge. the build failure is not related to this Pr