[GitHub] [incubator-nuttx] xiaoxiang781216 commented on pull request #1346: sched/kthread: extend kthread_create() to support configurable stack

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xiaoxiang781216 commented on pull request #1346:
URL: https://github.com/apache/incubator-nuttx/pull/1346#issuecomment-652555710


   > We have already gone throught this before with PR #1099 . I will not accept this change. The mechanism to provide a configurable status is already in place.
   > 
   > I provided in the instructions in that PR: Here is how you need to create a kernel thread with a custom stack:
   > 
   > ```
   > Allocate the TCB with kmm_zalloc().
   > Initialize the TCB. See binfmt/binfmt_execmodule.c for an example for ELF modules.
   > Make certain that the tcb->flags field is set to indicate a kernel thread:
   > Allocate a stack from whatever memory you wish.
   > Call task_init(), passing it the TCB, stack and other parameters.
   > Do another other things you would like, and finally
   > Call task_activate()
   > ```
   > 
   > That is the whole purpose of task_init(). Do not create other implementations with the correct implemtation is already in place.
   
   We need more discuss here: since you and many other people(include me) agree that the current kernel thread implemenation(reuse the most userspace task infrastructure) isn't a perfect solution and will most likely change in the furture.
   https://github.com/apache/incubator-nuttx/issues/1108
   If we encourage people directly go through task_init/task_activate for the kernel thread creation, this will make the redesgin more harder and from the desgin perspective:
   1.It's an internal design decision that kernel thread is build on top of task(I guess only few people know this fact), we shouldn't expose this detail to the normal developer.
   2.It's a very bad idea to give an offical guide(create the kernel thread through task_init/task_activate) but we have plan to modify the implementation in an incompatible way.
   3.It is a common requirement to create a thread(either kernel or pthread) with a custom stack, why we don't provide this functionality directly just like pthread API?
   So @patacongo please reconsider this patch again.


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