[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <Y9y/YVK1bcZgFCU2@Boquns-Mac-mini.local>
Date: Fri, 3 Feb 2023 00:01:37 -0800
From: Boqun Feng <boqun.feng@...il.com>
To: Greg KH <gregkh@...uxfoundation.org>
Cc: Miguel Ojeda <miguel.ojeda.sandonis@...il.com>,
Gary Guo <gary@...yguo.net>,
Peter Zijlstra <peterz@...radead.org>,
rust-for-linux@...r.kernel.org, linux-kernel@...r.kernel.org,
Will Deacon <will@...nel.org>,
Mark Rutland <mark.rutland@....com>,
Miguel Ojeda <ojeda@...nel.org>,
Alex Gaynor <alex.gaynor@...il.com>,
Wedson Almeida Filho <wedsonaf@...il.com>,
Björn Roy Baron <bjorn3_gh@...tonmail.com>,
Vincenzo Palazzo <vincenzopalazzodev@...il.com>
Subject: Re: [RFC 2/5] rust: sync: Arc: Introduces ArcInner::count()
On Fri, Feb 03, 2023 at 08:38:25AM +0100, Greg KH wrote:
[...]
> > Needless to say that ArcInner::count() can guarantee not reading 0
>
> How? Because you have an implicit reference on it already? If so, then
Yes, roughly a reference ("&") in Rust can be treated as a
compile-time reference count, so the existence of "&" in fact prevents
the underlying data from going away, or in Rust term, being "drop"ped.
To get a "&ArcInner<T>", we need a "&Arc<T>", and as long as there is
a reference to an "Arc<T>", the object won't be dropped, that's the
proof of the underly object still being referenced.
Other folks may explain this better and accurate, but that's the basic
idea ;-)
Regards,
Boqun
> 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 :)
>
[...]
> thanks,
>
> greg k-h
Powered by blists - more mailing lists