[PATCH] pthread_once hangs when init routine throws an exception [BZ #18435]

[Martin Sebor]

>> By removing the macro redefinitions from nptl/pthreadP.h
>> the change causes pthread_once.c to be compiled with the
>> more robust macros defined in pthread.h and allows cleanup
>> to take place even after an exception has been thrown so
>> long as glibc has been compiled with -fexceptions.
>
> they're in there to avoid the PLT right ?  so deleting them means the relocs
> come back.  can't we get both here ?

Looking at the powepc64 assembly for ___pthread_once_slow before
and after the change, there are no PLT calls in either. The only
difference is that with the change, the function calls GCC's
_Unwind_Resume which is a direct branch to the function.

Comparing the rest of libpthread.so before and after the change,
the number of calls via the PLT is the same.

I admit I'm not sure what the intended purpose of the internal
macros was. I had searched git logs before I made the change
but couldn't find anything helpful beyond some ChangeLog entries
that referred to it as an internal optimization. They seem to
have been introduced before 2001 (the year of the first Git
commit, AFAICS).

If I missed something let me know.

Martin