linux-kernel - Re: [PATCH 0/8] Introduce simple hazard pointers for lockdep

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <7f64c1bf-ae54-4bb0-b85d-d2a369596993@efficios.com>
Date: Thu, 26 Jun 2025 09:45:04 -0400
From: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
To: Christoph Hellwig <hch@...radead.org>, Boqun Feng <boqun.feng@...il.com>
Cc: linux-kernel@...r.kernel.org, rcu@...r.kernel.org, lkmm@...ts.linux.dev,
 Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...nel.org>,
 Will Deacon <will@...nel.org>, Waiman Long <longman@...hat.com>,
 Davidlohr Bueso <dave@...olabs.net>, "Paul E. McKenney"
 <paulmck@...nel.org>, Josh Triplett <josh@...htriplett.org>,
 Frederic Weisbecker <frederic@...nel.org>,
 Neeraj Upadhyay <neeraj.upadhyay@...nel.org>,
 Joel Fernandes <joelagnelf@...dia.com>, Uladzislau Rezki <urezki@...il.com>,
 Steven Rostedt <rostedt@...dmis.org>, Lai Jiangshan
 <jiangshanlai@...il.com>, Zqiang <qiang.zhang@...ux.dev>,
 Breno Leitao <leitao@...ian.org>, aeh@...a.com, netdev@...r.kernel.org,
 edumazet@...gle.com, jhs@...atatu.com, kernel-team@...a.com,
 Erik Lundgren <elundgren@...a.com>
Subject: Re: [PATCH 0/8] Introduce simple hazard pointers for lockdep

On 2025-06-26 06:16, Christoph Hellwig wrote:
> On Wed, Jun 25, 2025 at 07:08:57AM -0700, Boqun Feng wrote:
>> Sure, I will put one for the future version, here is the gist:
> 
> Thanks a lot!
> 
>> The updater's wait can finish immediately if no one is accessing 'a', in
>> other words it doesn't need to wait for reader 2.
> 
> So basically it is the RCU concept, but limited to protecting exactly
> one pointer update per critical section with no ability for the read
> to e.g. acquire a refcount on the objected pointed to by that pointer?

FWIW, hazard pointers can be chained with other existence guarantee
mechanisms. I've done prototypes that use hazard pointers chained
with a reference counter in the object to implement something similar to
smart pointers. Let me know if you are interested in the details.

Thanks,

Mathieu

-- 
Mathieu Desnoyers
EfficiOS Inc.
https://www.efficios.com