endless loop in stock interrupt handler

I don't know freeRTOS, but you must be very careful in using interrupt control functions with an underlying OS.

Infact, an OS relies on a high priority irq to schedule application tasks; application usually doesn't work with irq at the raw level, but the OS emulates the required hw behaviour through sort virtual IRQs and the scheduling process.

For example, if you use sys timer irq or any other device required by OS, you may corrupt the OS itself and your system would stop working.

What I mean is that under an OS, using raw IRQs is possible but is not recommended unless you have a comprehensive knowledge of your OS's ineer workings and you are aware of what you are doing.