Pi4 64 bit OS: Carrier Not Turning Off, High CPU usage

[aaknitt]

I'm running on a Pi4 with 64 bit OS by compiling use the makefile in #102

Problem 1: CPU usage is extremely high when running PiFmAdv, causing responsiveness and connectivity issues with the Pi. VNC connections drop, terminal is very sluggish to respond, etc.

Problem 2: When I exit the program using CTRL-C, the carrier stays active even though the terminal says that the carrier should be killed. I have instrumented the terminate() function with additional printf statements and confirmed that all of the "if" statements in that function are being entered. Running PiFmAdv again with --gpclk set to 1 or 2 makes the carrier go away (is it going somewhere else? I'm not sure), but CPU usage remains high.

Problem 3: High CPU usage persists after the program has been killed using CTRL-C. systemd and kworker processes are using nearly all CPU. Only solution is to reboot the Pi4, which takes much, much longer than normal to do cleanly.

Not sure it matters, but I'm also seeing the same problem as reported in #92 with a message that says "Alert: 8 samples over deviation"