Re: newlib reentrancy question

["J. Johnston" <jjohnstn at cygnus dot com>]

Joel Sherrill wrote:
> 
> Where's the best description and/or example of how to
> implement newlib pre-thread reentrancy support these
> days?
> 
> I am investigating a case where cout does not work
> for the 2nd task in a system unless the 1st task
> uses it.  All of the standard C routines work fine.
> In fact, the printf immediately before the cout calls
> in the 2nd task prints.  The clue I think is that
> printf does not call fwrite and cout does.  Here
> is how we do the per-task reentrancy structures
> now.
> 
> + At system initialization, we use a global struct _reent.
>   It is initialized using _REENT_INIT.
> 
> + Each task has its own copy of the reent structure.
> 
> + As part of a context switch the contents of _impure_ptr
> are switched.
> 
> + As each task begins execution time, the following code
> is executed:
> 
>   ptr = (struct _reent *) calloc(1, sizeof(struct _reent));
>   *ptr = (struct _reent) _REENT_INIT((*ptr));
> 
> What seems to be happening is that the 2nd task gets to
> CHECK_INIT:
> 
> #define CHECK_INIT(fp) \
>   do                                    \
>     {                                   \
>       if ((fp)->_data == 0)             \
>         (fp)->_data = _REENT;           \
>       if (!(fp)->_data->__sdidinit)     \
>         __sinit ((fp)->_data);          \
>     }                                   \
>   while (0)
> 
> and it decides to do the copy in the first if.  But since
> _REENT_INIT at task_begin time set __sdidinit to 1, it
> skips the __sinit portion.  Any ideas?  Do you think
> that our per-task initialization should be different
> and make sure __sdidinit is 0?
> 
>

Please clarify.  The _REENT_INIT macro in newlib/libc/include/sys/reent.h initializes __sdidinit to
0.  Have you modified this in your copy?

-- Jeff J.