[GitHub] [incubator-nuttx] xiaoxiang781216 edited a comment on pull request #1922: sched: nxtask_start should call entry point directly for kernel thread

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xiaoxiang781216 edited a comment on pull request #1922:
URL: https://github.com/apache/incubator-nuttx/pull/1922#issuecomment-705357685


   > @xiaoxiang781216
   > 
   > As long as I checked the latest upstream, I think the issue does not relate to SMP.
   
   Yes, it isn't SMP specific. SMP just expose the problem:
   Two CPUs idle thread call nxtask_startup->cxx_initialize at the same time which make all global constructors are executed twice.
   But the real issue is that we shouldn't initialize C++ global variables inside kernel space at all, because all kernel threads(include idle thread) shouldn't use any C++ element at all).
   
   The good side effect with this fix is that the synchronization issue also get resolved too, because kernel always create one and only one user task(init) and cxx_initialize get called before init's main has the chance to create more tasks concurrently.
   
   > Actually the issue happens with lm3s6965-ek:discover configuration.
   > 
   > Also, I noticed that this PR only resolves the issue for kernel thread as titled.
   > However, for example, lm3s6965-ek:discover creates 'Telnet daemon' which
   > will call cxx_initialize() in nxtask_startup().
   
   Yes, it is the expected behaviour, please see PR: https://github.com/apache/incubator-nuttx/pull/1341 and https://github.com/apache/incubator-nuttx-apps/pull/316. The motivation is centralize the c++ initialization to common place. 


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