Nikos Mavrogiannopoulos <[email protected]> writes:
> Is that really needed? I mean you are setting these values at the constructor,
> that is prior to any thread being created, and there shouldn't be
> multiple CPUs to
> worry about.
If the constructor thing works, it's no problem. And if ifunc is
supported, I don't know how that really works, but I imagine the dynamic
loader serializes calls to the resolver functions, and that whatever
magic is used in the case of static libraries also is no problem.
So remains the case of no C extensions, where the initialization is
hooked in via the initial values of all function pointers (the way it's
done in GMP). Here, all bets on the timing of calls are off, the
application can spawn multiple threads, and have the threads all call
nettle for the first time.
So the problem is a bit obscure, but I think if we just replace
initialized = 1 by _nettle_synchronous_write (&initialized, 1),
implemented as
_nettle_synchronous_write:
mfence
movl %esi, (%rdi)
mfence
it will be safe in all cases.
Regards,
/Niels
--
Niels Möller. PGP-encrypted email is preferred. Keyid C0B98E26.
Internet email is subject to wholesale government surveillance.
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