While working on the interpreter management of mod_perl I saw various invocations of PERL_SET_CONTEXT(aTHX).

For example 

    if (r || c) {
        interp = modperl_interp_select(r, c, s);
        aTHX = interp->perl;
    }
    else {
        /* Child{Init,Exit}, OpenLogs */
        aTHX = scfg->mip->parent->perl;
        PERL_SET_CONTEXT(aTHX);
    }

[download]

So, what does PERL_SET_CONTEXT do? Why is it called in the else branch but not in the if? Is that maybe an error?

When do I have to call PERL_SET_CONTEXT? Is it an expensive operation? Wouldn't it be right to call it each time an interpreter is selected for a certain task?

Thanks,
Torsten

In reply to What is PERL_SET_CONTEXT for? by tfoertsch

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