From: Jonas Oberhauser <jonas.oberhauser@huawei.com>
To: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
Jonas Oberhauser <jonas.oberhauser@huaweicloud.com>,
Boqun Feng <boqun.feng@gmail.com>,
"Paul E. McKenney" <paulmck@kernel.org>
Cc: "lkmm@lists.linux.dev" <lkmm@lists.linux.dev>,
Olivier Dion <odion@efficios.com>
Subject: RE: [RFC PATCH 1/1] hpref: Hazard Pointers with Reference Counter
Date: Wed, 7 Jan 2026 09:38:53 +0000 [thread overview]
Message-ID: <c7464e0027f9403191d0d3638558bccd@huawei.com> (raw)
In-Reply-To: <4d234ab6-de1a-4959-81f7-37c5b41c6c66@efficios.com>
> Sorry for the (very) late reply. :)
A blast from the past :)) Thanks for the response.
> liburcu uatomics and "cmm_*" API initially aimed to replicate the LKMM in userspace (note: this was done circa 2009). However, starting from liburcu 0.15, we extended the uatomics API to support the C11 model
I expect the C11-style-semantics will have a lot of friction with RCU (at the least because of missing dependency ordering). Things like rmb and wmb may also not have a clean formalization in a C11-style semantics.
> with an additional "CMM_SEQ_CST_FENCE" which aims to fill the gap between LKMM and C11.
I see, thanks!
Have a lot of fun,
jonas
-----Original Message-----
From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Sent: Tuesday, January 6, 2026 3:53 PM
To: Jonas Oberhauser <jonas.oberhauser@huaweicloud.com>; Boqun Feng <boqun.feng@gmail.com>; Paul E. McKenney <paulmck@kernel.org>
Cc: lkmm@lists.linux.dev; Olivier Dion <odion@efficios.com>
Subject: Re: [RFC PATCH 1/1] hpref: Hazard Pointers with Reference Counter
On 2024-09-30 09:31, Jonas Oberhauser wrote:
> [dropping a lot of CC]
>
> Am 9/21/2024 um 6:42 PM schrieb Mathieu Desnoyers:
>>
>> Porting it to the Linux kernel should be straightforward.
>
>
> Btw, what is the relation between uatomics and LKMM?
>
> Should I assume that they intend to have LKMM semantics modulo
> whatever is explained here:
>
> https://github.com/urcu/userspace-rcu/blob/master/doc/uatomic-api.md
>
> Because on C11 model, dependencies are generally not considered
liburcu uatomics and "cmm_*" API initially aimed to replicate the LKMM in userspace (note: this was done circa 2009). However, starting from liburcu 0.15, we extended the uatomics API to support the C11 model, with an additional "CMM_SEQ_CST_FENCE" which aims to fill the gap between LKMM and C11.
Starting from liburcu 0.15, you can configure the library with:
--enable-compiler-atomic-builtins: Enable the use of compiler
atomic builtins.
Without this configure flag, the legacy custom assembly atomics are still used.
Thanks,
Mathieu
--
Mathieu Desnoyers
EfficiOS Inc.
https://www.efficios.com
next prev parent reply other threads:[~2026-01-07 9:38 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-09-21 16:42 [RFC PATCH 1/1] hpref: Hazard Pointers with Reference Counter Mathieu Desnoyers
2024-09-21 21:07 ` Lai Jiangshan
2024-09-22 7:47 ` Mathieu Desnoyers
2024-09-25 5:57 ` Jonas Oberhauser
2024-09-25 6:35 ` Mathieu Desnoyers
2024-09-25 10:06 ` Jonas Oberhauser
2024-09-25 11:36 ` Mathieu Desnoyers
2024-09-25 12:02 ` Jonas Oberhauser
2024-09-28 11:22 ` Jonas Oberhauser
2024-09-28 11:33 ` Mathieu Desnoyers
2024-09-28 11:50 ` Jonas Oberhauser
2024-09-30 13:31 ` Jonas Oberhauser
2024-10-01 15:24 ` Paul E. McKenney
2026-01-06 14:52 ` Mathieu Desnoyers
2026-01-07 9:38 ` Jonas Oberhauser [this message]
2026-01-07 14:40 ` Mathieu Desnoyers
2026-01-07 17:48 ` Paul E. McKenney
2026-01-07 20:04 ` Mathieu Desnoyers
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