Error when rebooting the frdm_k64f board

[chtavares]

Hello, I have a question, if anyone can help me I will be very happy. I have an application on zephyr, that downloads an image and saves it in flash area 1. I use the last mcuboot and the board is frdm_k64f. When I rebooted happens that error bellow:

[00:00:00.004,948] <inf> mcuboot: Starting bootloader
[00:00:00.010,967] <inf> mcuboot: Image 0: magic=good, copy_done=0x3, image_ok=0x1
[00:00:00.018,793] <inf> mcuboot: Scratch: magic=unset, copy_done=0x5b, image_ok=0x3
[00:00:00.016,952] <inf> mcuboot: Boot source: slot 0
[00:00:00.014,445] <inf> mcuboot: Swap type: test
***** BUS FAULT *****
  Imprecise data bus error
***** Hardware exception *****
Current thread ID = 0x00000000
Faulting instruction address = 0x3ebe

I don't know why it happens.
So, I used the git bisect to find where started the problem, and the commit is:

commit dc0713a706e7e2898c172c6c0965b1b784859841
Author: Andy Ross <andrew.j.ross@intel.com>
Date:   Thu Jul 5 12:50:41 2018 -0700

    kernel: Cleanup. Remove redundant test when calling _Swap()
    
    _Swap() must already handle the case where _get_next_ready_thread() is
    the same as _current.
    
    Signed-off-by: Andy Ross <andrew.j.ross@intel.com>

Unfortunately, I don't know how to solve it.

[MaureenHelm]

This is caused by the mcux flash driver using a semaphore while mcuboot/zephyr has multithreading disabled. We can either enable multithreading in mcuboot or modify the mcux flash driver similar to 408ea14.

[chtavares]

@MaureenHelm, I changed that on mcuboot, and that worked fine, thanks for your help.

[d3zd3z]

How much does this change the code size? Normally, we'd really like to be able to build MCUboot without multi-threading, as it isn't needed, and we want the bootloader to be as small as possible.

[d3zd3z]

Wouldn't it be better to fix the semaphore/locking code to not crash if multithreading isn't enabled?

[mike-scott]

@d3zd3z I put up a PR to fix the flash driver for when CONFIG_MULTITHREADED=n

[d3zd3z]

Aside from the fact that semaphores != mutexes, but that is a deeper issue throughout much of the code.