On Wed, Jul 28, 2021 at 1:16 PM Seebs <se...@seebs.net> wrote:
>
> On Wed, 28 Jul 2021 11:36:22 +0200
> "Damian Wrobel" <dwro...@ertelnet.rybnik.pl> wrote:
>
> > Do I correctly assume that pseudo_client_op() has to be fully
> > reentrant?
>
> No. It's never been even a tiny bit reentrant. We used to do the
> allocate and free thing, and it was incredibly expensive, and the
> nature of the thing requires confidence that we never, ever, have
> more than one thing writing and reading over the socket at a time,
> so it's just Not Reentrant. During one call to pseudo_client_op,
> there will never be another, and all the IPC stuff uses a single
> consistent local buffer that it returns the address of.
>
> Declaring that as static without changing the initializer would indeed
> break everything -- we rely on the initializer working. Changing it to
> static means it only gets initialized once...
>
> Changing it to:
>
> static pseudo_msg_t msg;
> msg = pseudo_msg_t { .type = PSEUDO_MSG_OP };
>
> would probably be fine, because then it'd be initialized. Otherwise,
> we'd get failures when msg got overwritten and reused.
>
> Or just changing `result = &msg` to something like `result =
> &xattrdb_data`, which would be nonsensical but it turns out not to
> matter, as the only caller that reaches this case is the caller
> that's just checking yes/no "is the return value not a null pointer".
If the caller only cares about yes/no then how about returning 1/0
instead of a pointer?
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