NRF_LOG_INFO() not printing to debug terminal

[ryerye120]

I'm having some issues with the printing to the debug terminal. I'm using SDK16 with SES 4.5 and developing on the nrf52840 DK. 

I followed the instructions in this video: https://youtu.be/uP8RYgYGRvI?t=179  in addition to the addendums on this thread as well as this other thread: https://devzone.nordicsemi.com/f/nordic-q-a/58414/enabling-nrf_log_enabled-to-log-messages-on-debug-terminal . I'm playing with the SPI master and slave examples and wanted to see what I was actually sending between the boards (the LEDs toggle just fine so it works but I want to see the actual data in the debug terminal). I haven't touched anything serious in the examples, and am still using the existing NRF_LOG_INFO() print statements. Unfortunately, I don't see anything in the debug terminal! Not even the initial "SPI example started"!!

Currently, I have enabled NRF_LOG_BACKEND_RTT_ENABLED as well as the NRF_LOG_ENABLED. I have also disabled NRF_LOG_BACKEND_UART_ENABLED just in case. Have I missed something simple?

[ryerye120]

So I went through my sdk_config and set NRF_LOG_DEFERRED to 0. This seems to have fixed my issue.

Before I did this (NRF_LOG_DEFERRED = 1), I placed NRF_LOG_FLUSH() after ever NRF_LOG_INFO(). This seemed to work at first, but if I placed this in an interrupt then my code would hang. What does NRF_LOG_FLUSH() do?