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From:   Marco Elver <elver@google.com>
Date:   Thu, 6 Apr 2023 13:21:28 +0200
Message-ID: <CANpmjNPrREVGC3Az0T7k_2yr1PJp+E4yURUGUnu9Jb_CShJNHw@mail.gmail.com>
Subject: Re: [PATCH v2 03/13] rust: lock: introduce `Mutex`
To:     David Laight <David.Laight@aculab.com>
Cc:     Peter Zijlstra <peterz@infradead.org>,
        Wedson Almeida Filho <wedsonaf@gmail.com>,
        Greg KH <gregkh@linuxfoundation.org>,
        "rust-for-linux@vger.kernel.org" <rust-for-linux@vger.kernel.org>,
        Miguel Ojeda <ojeda@kernel.org>,
        Alex Gaynor <alex.gaynor@gmail.com>,
        Boqun Feng <boqun.feng@gmail.com>, Gary Guo <gary@garyguo.net>,
        =?UTF-8?Q?Bj=C3=B6rn_Roy_Baron?= <bjorn3_gh@protonmail.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Wedson Almeida Filho <walmeida@microsoft.com>,
        Ingo Molnar <mingo@redhat.com>, Will Deacon <will@kernel.org>,
        Waiman Long <longman@redhat.com>
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On Thu, 6 Apr 2023 at 10:38, David Laight <David.Laight@aculab.com> wrote:
>
> From: Peter Zijlstra
> > Sent: 05 April 2023 21:50
> >
> > On Wed, Apr 05, 2023 at 05:40:39PM -0300, Wedson Almeida Filho wrote:
> ...
> > > So the situation is improved in that we don't need to manually write (and
> > > commit) the helpers. It may improve further in the future if we get better
> > > integration of the languages.
> >
> > But yeah, feel free to convert macros to inline functions where the
> > difference is moot. There is indeed no real reason for mutex_lock() to
> > not be an inline function in that case.
>
> mutex_lock() is probably ok.
> But there are cases where gcc generates much better code
> for #defines than for inline functions.
> Almost certainly because the front end gets to optimise
> #defines, but inlines are done much later on.

For macro to inline function conversions, the most conservative option
would be __always_inline. We've also seen things go wrong with
"inline" only paired with various kinds of instrumentation.

Can bindgen deal with "static __always_inline" functions?