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	Sat, 21 Dec 2024 11:22:40 -0500 (EST)
From: Olivier Dion <odion@efficios.com>
To: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
 linux-kernel@vger.kernel.org, lttng-dev@lists.lttng.org
Cc: =?utf-8?B?T25kxZllaiBTdXLDvQ==?= <ondrej@isc.org>, paulmck
 <paulmck@kernel.org>, Alan Stern
 <stern@rowland.harvard.edu>, Lai Jiangshan <jiangshanlai@gmail.com>, Brad
 Smith <brad@comstyle.com>, lwn@lwn.net
Subject: Re: [RELEASE] Userspace RCU 0.15.0
In-Reply-To: <51160e24-389a-41b6-871b-ba522d427220@efficios.com>
Organization: EfficiOS
References: <51160e24-389a-41b6-871b-ba522d427220@efficios.com>
Date: Sat, 21 Dec 2024 11:22:40 -0500
Message-ID: <87ed21hupb.fsf@laura>
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On Fri, 20 Dec 2024, Mathieu Desnoyers <mathieu.desnoyers@efficios.com> wrote:
> Hi,
[...]
>    * Introduction of the CMM memory model with the following new primitives:
>      
>        - uatomic_load(addr, memory_order)
>      
>        - uatomic_store(addr, value, memory_order)
>        - uatomic_and_mo(addr, mask, memory_order)
>        - uatomic_or_mo(addr, mask, memory_order)
>        - uatomic_add_mo(addr, value, memory_order)
>        - uatomic_sub_mo(addr, value, memory_order)
>        - uatomic_inc_mo(addr, memory_order)
>        - uatomic_dec_mo(addr, memory_order)
>      
>        - uatomic_add_return_mo(addr, value, memory_order)
>        - uatomic_sub_return_mo(addr, value, memory_order)
>      
>        - uatomic_xchg_mo(addr, value, memory_order)
>      
>        - uatomic_cmpxchg_mo(addr, old, new,
>                             memory_order_success,
>                             memory_order_failure)
>
> The uatomic API was extended to support explicit memory ordering.
> For instance, the previous uatomic_cmpxchg() now has a
> uatomic_cmpxchg_mo() counterpart, which takes a memory ordering
> argument.

It is worth mentioning that the `*_mo' variants are not public API.
Instead, the current uatomic API is extended by adding an optional
memory odring parameter for the various atomic operation.

For example, uatomic_xchg(addr, value) is equivalent to
uatomic_xchg(addr, value, CMM_SEQ_CST_FENCE).  But user can choose a
different memory ordering.  For example: uatomix_xchg(addr, value,
CMM_RELEASE).

[...]

Thanks,
Olivier
-- 
Olivier Dion
EfficiOS Inc.
https://www.efficios.com