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

From: Boqun Feng
Date: Mon Oct 25 2021 - 10:55:05 EST


Hi,

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

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

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

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