From: Josh Stone <jistone@redhat.com>
To: Greg KH <gregkh@linuxfoundation.org>, Boqun Feng <boqun.feng@gmail.com>
Cc: "Miguel Ojeda" <miguel.ojeda.sandonis@gmail.com>,
"Gary Guo" <gary@garyguo.net>,
"Peter Zijlstra" <peterz@infradead.org>,
rust-for-linux@vger.kernel.org, linux-kernel@vger.kernel.org,
"Will Deacon" <will@kernel.org>,
"Mark Rutland" <mark.rutland@arm.com>,
"Miguel Ojeda" <ojeda@kernel.org>,
"Alex Gaynor" <alex.gaynor@gmail.com>,
"Wedson Almeida Filho" <wedsonaf@gmail.com>,
"Björn Roy Baron" <bjorn3_gh@protonmail.com>,
"Vincenzo Palazzo" <vincenzopalazzodev@gmail.com>
Subject: Re: [RFC 2/5] rust: sync: Arc: Introduces ArcInner::count()
Date: Fri, 3 Feb 2023 11:17:47 -0800 [thread overview]
Message-ID: <9d144ca0-5cf2-a575-a30b-22f5ff4e8e2b@redhat.com> (raw)
In-Reply-To: <Y9y58cy1GKZLdyjb@kroah.com>
On 2/2/23 11:38 PM, Greg KH wrote:
> How? Because you have an implicit reference on it already? If so, then
> why does reading from it matter at all, as if you have a reference, you
> know it isn't 0, and that's all that you can really care about. You
> don't care about any number other than 0 for a reference count, as by
> definition, that's what a reference count does :)
There is an additional ability for 1, mentioned up thread -- if you have
&mut Arc<T>, and the inner count is 1, then you *know* there aren't any
other Arc<T> handles anywhere else. Then it is safe to return an
exclusive &mut T, like the upstream Arc::get_mut and Arc::make_mut. This
can also be used for owned Arc<T> like the upstream Arc::try_unwrap.
next prev parent reply other threads:[~2023-02-03 19:18 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-02-01 23:22 [RFC 0/5] rust: sync: Arc: Implement Debug and Display Boqun Feng
2023-02-01 23:22 ` [RFC 1/5] rust: sync: impl Display for {Unique,}Arc Boqun Feng
2023-02-02 14:15 ` Gary Guo
2023-02-02 16:50 ` Björn Roy Baron
2023-02-04 10:20 ` Finn Behrens
2023-02-04 18:47 ` Vincenzo Palazzo
2023-02-01 23:22 ` [RFC 2/5] rust: sync: Arc: Introduces ArcInner::count() Boqun Feng
2023-02-02 9:14 ` Peter Zijlstra
2023-02-02 13:46 ` Boqun Feng
2023-02-02 14:21 ` Gary Guo
2023-02-02 15:41 ` Greg KH
2023-02-02 16:10 ` Boqun Feng
2023-02-02 16:17 ` Greg KH
2023-02-02 16:51 ` Boqun Feng
2023-02-02 21:47 ` Miguel Ojeda
2023-02-03 5:22 ` Greg KH
2023-02-03 7:25 ` Boqun Feng
2023-02-03 7:38 ` Greg KH
2023-02-03 7:43 ` Boqun Feng
2023-02-03 8:01 ` Boqun Feng
2023-02-03 19:17 ` Josh Stone [this message]
2023-02-03 19:22 ` Wedson Almeida Filho
2023-02-02 14:22 ` Gary Guo
2023-02-04 18:48 ` Vincenzo Palazzo
2023-02-01 23:22 ` [RFC 3/5] rust: sync: Arc: Introduces Arc::get_inner() helper Boqun Feng
2023-02-02 14:24 ` Gary Guo
2023-02-02 16:53 ` Björn Roy Baron
2023-02-04 18:51 ` Vincenzo Palazzo
2023-02-01 23:22 ` [RFC 4/5] rust: sync: impl Debug for {Unique,}Arc Boqun Feng
2023-02-02 14:28 ` Gary Guo
2023-02-03 19:46 ` Boqun Feng
2023-02-04 18:56 ` Vincenzo Palazzo
2023-02-01 23:22 ` [RFC 5/5] sample: rust: print: Add sampe code for Arc printing Boqun Feng
2023-02-02 16:56 ` Björn Roy Baron
2023-02-04 10:22 ` Finn Behrens
2023-02-04 19:05 ` Vincenzo Palazzo
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