Thread Local Storage

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Jmfrey

• December 18, 2015 04:56

With Crossworks 3.0 for MSP430 and CTL the thread local storage now has a special section in, what seems, is a way to allow for an arbitrary amount of thread local storage.

I am not sure how one is supposed to use this from C.

Presumable one puts a variable in the THREAD section and then accesses it through the CTL_TASK_t structure for each task. 

I think I can do the first part, put a variable into the THREAD section but, I am unsure how to access it in a reliable manner. Presumable one would calculate the offset from the beginning of the THREAD section and use that to access the thread local storage. My attempt at this failed and I am unable to proceed.

I have declared the following:

extern unsigned char thread_init_begin;

#pragma dataseg("THREAD")
  unsigned char thread_test=0;
#pragma dataseg(default)

And I attempt to access them in the following manner:

printf("thread_test = %p\r\n""thread_init_begin = %p\r\n""offset = %p\r\n",&thread_test,&thread_init_begin,&thread_test-&thread_init_begin);

The code compiles fine but the linker complains of "undefined symbol '_thread_init_begin. This is obvously because of the preceding underscore but, I don't know how to remove it as it is automatically inserted by the compiler.

Is there an example out there of how to access and use the thread local storage? I have googled it an returned very few references to thread local storage.

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  Michael Johnson

  • December 18, 2015 08:02

  __thread int x;

  should do it.

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  Jmfrey

  • December 18, 2015 19:03

  Thanks, that was easier than expected!

  I still find no mention of this in the documentation. Is it actually documented somewhere?

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