So we add more check not only UART_MSR_ANY_DELTA but also with
comparing DCD/RI/DSR/CTS change with old value. Due to the state
bit is always correct, we direct save msr when read.
The following step to reproduce this problem with while loop step 1~4:
1. ioctl(fd, TIOCMSET, &data) to set RTS or DTR
2. ioctl(fd, TIOCMGET, &data) to read CTS or DCD/DSR state
3. ioctl(fd, TIOCMSET, &data) to unset RTS or DTR
4. ioctl(fd, TIOCMGET, &data) to read CTS or DCD/DSR state
Without having looked at this very closely; are you sure this is a
hardware issue and not related to the locking issues I pointed at in my
comments to tiocmset?