Description

While running tests/trickle for #8904 on mega-xplained, I have run into a number of different issues. One issue is that prev_now is not being initialized properly in main (it assumes xtimer_now_usec is zero when main starts, which is not the case). This is easily fixed by adding prev_now = xtimer_now_usec(); to the beginning of main. There are also a number of problems where it hangs at various points.

Steps to reproduce the issue

Run tests/trickle with the following variations:

• trunk on mega-xplained
• cpu/atmega_common: return to non-interrupt context swaps #8904 applied to trunk on mega-xplained
• trunk on mega-xplained with prev_now = xtimer_now_usec();
• cpu/atmega_common: return to non-interrupt context swaps #8904 applied to trunk on mega-xplained with prev_now = xtimer_now_usec();

Expected results

tests/trickle runs, printing 5 messages after [START], and then 7 messages after [TRICKLE_RESET], and then prints [SUCCESS].

Actual results

• Trunk hangs after [TRICKLE_RESET]
• cpu/atmega_common: return to non-interrupt context swaps #8904 applied to trunk declares failure (due to not initializing prev_now properly)
• Trunk with prev_now initialized hangs after three messages (I think this is a cpu/atmega_common: Context switching race condition #8896 related problem, and is fixed by cpu/atmega_common: return to non-interrupt context swaps #8904).
• cpu/atmega_common: return to non-interrupt context swaps #8904 applied to trunk and prev_now initialized hangs after [TRICKLE_RESET]

Versions

Board: mega-xplained

Installed compiler toolchains 
-----------------------------
             native gcc: missing
      arm-none-eabi-gcc: missing
                avr-gcc: avr-gcc (Fedora 7.2.0-1.fc27) 7.2.0
       mips-mti-elf-gcc: missing
             msp430-gcc: missing
   riscv-none-embed-gcc: missing
                  clang: missing

Installed compiler libs
-----------------------
   arm-none-eabi-newlib: missing
    mips-mti-elf-newlib: missing
riscv-none-embed-newlib: missing
               avr-libc: "2.0.0" ("20150208")

Installed development tools
---------------------------
                  cmake: cmake version 3.11.0
               cppcheck: missing
                doxygen: missing
                 flake8: missing
                    git: git version 2.14.2
             coccinelle: missing