linux-kernel - Re: [PATCH v10 1/5] rust: add static_branch_unlikely for static_key

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Message-ID: <20241011171251.0bd53f01@eugeo>
Date: Fri, 11 Oct 2024 17:12:51 +0100
From: Gary Guo <gary@...yguo.net>
To: Sami Tolvanen <samitolvanen@...gle.com>
Cc: Alice Ryhl <aliceryhl@...gle.com>, Steven Rostedt <rostedt@...dmis.org>,
 Masami Hiramatsu <mhiramat@...nel.org>, Mathieu Desnoyers
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 loongarch@...ts.linux.dev
Subject: Re: [PATCH v10 1/5] rust: add static_branch_unlikely for
 static_key_false

On Fri, 11 Oct 2024 08:23:18 -0700
Sami Tolvanen <samitolvanen@...gle.com> wrote:

> On Fri, Oct 11, 2024 at 5:13 AM Gary Guo <gary@...yguo.net> wrote:
> >
> > On Fri, 11 Oct 2024 10:13:34 +0000
> > Alice Ryhl <aliceryhl@...gle.com> wrote:
> >  
> > > +#ifndef CONFIG_JUMP_LABEL
> > > +int rust_helper_static_key_count(struct static_key *key)
> > > +{
> > > +     return static_key_count(key);
> > > +}
> > > +EXPORT_SYMBOL_GPL(rust_helper_static_key_count);  
> >
> > ^ Explicit export should be removed. This only works because we didn't
> > remove export.h from all helpers.c yet, but there's a patch to do
> > that and this will stop working.  
> 
> What's the benefit of removing explicit exports from the Rust helper C
> code? It requires special casing things like modversions for these
> files, so I assume there's a reason for this. I asked about it here,
> but never got a response:
> 
> https://lore.kernel.org/rust-for-linux/CABCJKudqAEvLcdqTqyfE2+iW+jeqBpnTGgYJvrZ0by6hGdfevQ@mail.gmail.com/
> 
> Sami

Ah, I didn't saw that email, probably because I archived the mails after
the patch is applied.

We're working towards having an option that enables inlining these
helpers into Rust; when that option is enabled, the helpers must not be
exported. See
https://lore.kernel.org/rust-for-linux/20240529202817.3641974-1-gary@garyguo.net/
and https://lwn.net/Articles/993163/.

It's also quite tedious for every helper to carry this export.

Best,
Gary