linux-kernel - Re: [PATCH v3 12/13] rust: sync: reduce stack usage of `UniqueArc::try_new

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Message-ID: <3c628166-b836-4ea8-bc4b-d25902e75b49@ryhl.io>
Date:   Fri, 31 Mar 2023 09:05:26 +0200
From:   Alice Ryhl <alice@...l.io>
To:     y86-dev@...tonmail.com
Cc:     rust-for-linux@...r.kernel.org, linux-kernel@...r.kernel.org,
        patches@...ts.linux.dev, Miguel Ojeda <ojeda@...nel.org>,
        Alex Gaynor <alex.gaynor@...il.com>,
        Wedson Almeida Filho <wedsonaf@...il.com>,
        Boqun Feng <boqun.feng@...il.com>, Gary Guo <gary@...yguo.net>,
        Björn Roy Baron <bjorn3_gh@...tonmail.com>
Subject: Re: [PATCH v3 12/13] rust: sync: reduce stack usage of
 `UniqueArc::try_new_uninit`

On 3/30/23 00:33, y86-dev@...tonmail.com wrote:
> From: Benno Lossin <y86-dev@...tonmail.com>
> 
> `UniqueArc::try_new_uninit` calls `Arc::try_new(MaybeUninit::uninit())`.
> This results in the uninitialized memory being placed on the stack,
> which may be arbitrarily large due to the generic `T` and thus could
> cause a stack overflow for large types.
> 
> Change the implementation to use the pin-init API which enables in-place
> initialization. In particular it avoids having to first construct and
> then move the uninitialized memory from the stack into the final location.
> 
> Signed-off-by: Benno Lossin <y86-dev@...tonmail.com>

Reviewed-by: Alice Ryhl <aliceryhl@...gle.com>