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
``` python3
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()
```
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