[RFC v2 0/3] memory model: Make unlock(A)+lock(B) on the same CPU RCtso

From: Boqun Feng <boqun.feng@gmail.com>
To: linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org,
	linux-doc@vger.kernel.org
Cc: "Paul E . McKenney " <paulmck@kernel.org>,
	Dan Lustig <dlustig@nvidia.com>, Will Deacon <will@kernel.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Alexander Shishkin <alexander.shishkin@linux.intel.com>,
	Peter Anvin <hpa@zytor.com>,
	Andrea Parri <parri.andrea@gmail.com>,
	Ingo Molnar <mingo@kernel.org>,
	Vince Weaver <vincent.weaver@maine.edu>,
	Thomas Gleixner <tglx@linutronix.de>,
	Jiri Olsa <jolsa@redhat.com>,
	Arnaldo Carvalho de Melo <acme@redhat.com>,
	Stephane Eranian <eranian@google.com>,
	palmer@dabbelt.com, paul.walmsley@sifive.com, mpe@ellerman.id.au,
	Jonathan Corbet <corbet@lwn.net>,
	Boqun Feng <boqun.feng@gmail.com>
Subject: [RFC v2 0/3] memory model: Make unlock(A)+lock(B) on the same CPU RCtso
Date: Mon, 25 Oct 2021 22:54:13 +0800	[thread overview]
Message-ID: <20211025145416.698183-1-boqun.feng@gmail.com> (raw)

Hi,

Just a new version trying to make forward progress on this  ;-)

v1: https://lore.kernel.org/lkml/20210930130823.2103688-1-boqun.feng@gmail.com/

Changes since v1:

*	Split the patch into three to help resolve the litmus test
	addition discussion.
*	Add some explanation in patch #2 on the requirement of tests in
	litmus-tests directory.

To summarize the change in memory model, we now guarantee in the
following code:

	<memory access M>
	spin_unlock(A);
	spin_lock(B);
	<memory access N>

M is ordered against N unless M is a store and N is a load. More
detailed examples of this guarantee can be found in patch #3.

Architecture maintainers, appreciate it that you can take a look at
patch #3 and rest of whole set to confirm this guarantee works on your
architectures.

Alan, I split the patchset into three patches because I do think we need
some sort of patch #2 so that we can have consensus about whether merge
patch #3 or not. I know you want to keep litmus-tests directory as
simple as possible, but it won't hurt to document the requirement.
Looking forwards to your thoughts ;-)

Suggestion and comments are welcome!

Regards,
Boqun

Boqun Feng (3):
  tools/memory-model: Provide extra ordering for unlock+lock pair on the
    same CPU
  tools/memory-model: doc: Describe the requirement of the litmus-tests
    directory
  tools/memory-model: litmus: Add two tests for unlock(A)+lock(B)
    ordering

 .../Documentation/explanation.txt             | 44 +++++++++++--------
 tools/memory-model/README                     | 12 +++++
 tools/memory-model/linux-kernel.cat           |  6 +--
 ...LB+unlocklockonceonce+poacquireonce.litmus | 33 ++++++++++++++
 ...unlocklockonceonce+fencermbonceonce.litmus | 33 ++++++++++++++
 tools/memory-model/litmus-tests/README        |  8 ++++
 6 files changed, 114 insertions(+), 22 deletions(-)
 create mode 100644 tools/memory-model/litmus-tests/LB+unlocklockonceonce+poacquireonce.litmus
 create mode 100644 tools/memory-model/litmus-tests/MP+unlocklockonceonce+fencermbonceonce.litmus

-- 
2.33.0