ostest: Add initial support for CONFIG_BUILD_KERNEL

[pussuw]

Summary

Implement task_create and task_delete for use with ostest. The functions are unavailable in kernel build mode but overload them here and create a pthread worker instead. Some tests should be re-visited because the intent is to user another task (in this case another process) to e.g. receive signals. That will require quite a bit of extra work.

Tests that had to be disabled:

• waitpid: pthreads don't work with waitpid, but this can be fixed by starting a dummy process instead and using waitpid on that (NOT IMPLEMENTED)
• restart: task_restart() does not work at all with kernel mode so it is disabled entirely
• fpu: make sure the FPU test is not even attempted, because it will cause ASSERT() and stop the test
• vfork: vfork() does not work for some reason in CONFIG_BUILD_KERNEL, there is something missing on the kernel side, so just disable the test for now

Tests that should be re-visited:

• The signal tests, now they signal the process itself while before the signal was sent to another task. This will require building the part that receives the signal as a separate process
• waitpid: Like stated above, waitpid does not work for pthreads
• user_main: It might be a better idea to just call user_main() because the "test creating a task works"-part has already been tested; if ostest starts, then task starting and creation also works

Impact

Adds basic support for ostest with CONFIG_BUILD_KERNEL=y

Testing

icicle:knsh

[xiaoxiang781216]

Why not skip the test which involve task_xxx function instead simulating task by pthread?

[pussuw]

Why not skip the test which involve task_xxx function instead simulating task by pthread?

Of course that is another way of doing it. I thought this would be better, many tests create "workers" via task_create and I thought it would be fine to use pthreads for that.

We currently do not have any kind of ostest for CONFIG_BUILD_KERNEL, I made this to have at least something. It is not a full implementation but IMO better than nothing.

[xiaoxiang781216]

Why not skip the test which involve task_xxx function instead simulating task by pthread?

Of course that is another way of doing it. I thought this would be better, many tests create "workers" via task_create and I thought it would be fine to use pthreads for that.

If the case doesn't really depend on task_create, it's better to migrate to pthread or remove task_create calling directly.

We currently do not have any kind of ostest for CONFIG_BUILD_KERNEL, I made this to have at least something. It is not a full implementation but IMO better than nothing.

If the test invokes the function which is impossible to implement in kernel mode:

1. Change to the similar function exist in kernel mode
2. Skip the test by #ifdef CONFIG_BUILD_KERNEL if it indeed test the specific function

[pussuw]

If the case doesn't really depend on task_create, it's better to migrate to pthread or remove task_create calling directly.

I would have to go them through one by one, because I don't know how each test is supposed to work. Instead, I made a kludge solution that allows the test to compile and run (most) tests.

[pussuw]

If the test invokes the function which is impossible to implement in kernel mode:

1. Change to the similar function exist in kernel mode

The similar function is posix_spawn(), which requires:

• The test case is split into another (or perhaps even multiple) process's, compiled into a file, which can be started with posix_spawn()
• Potential communication between the two (or multiple) processes
  Achieving this kind of functionality is a lot of work which I'm not prepared to do at this point.

2. Skip the test by `#ifdef CONFIG_BUILD_KERNEL` if it indeed test the specific function

Skipping these kind of tests is fine by me, but I don't know which tests could be converted to use pthread and which must be skipped. I already disabled some of the tests that I know won't work in kernel mode.

[pussuw]

Btw, I 100% agree with you that this incomplete implementation is not perfect and needs more work + clean up.

I have been using this version for some time now and have found it useful (better than nothing) and I decided to make this PR to at least offer the solution to the community.

However, if no extra value is seen in this partial implementation, I will just close the PR.

Maybe at some point I will make a proper implementation for this, but as I said, I don't have time to do that now.

[xiaoxiang781216]

The patch is valuable. My suggestion is very simple that:

1. Remove user_main, let's start the test from main directly

2. Skip the test case which invoke the task_xxx function in kernel mode

   • Skip compiling from Make.defs
   • Skip inovation in ostest_main.c by #ifdef CONFIG_BUILD_KERNEL

Or provding a dummy function in the individual test source code

4. Remove the task_xxx simulation layer

We can migrate task_create to posix_spawn or pthread_create as needed in the future.