From: Boqun Feng <boqun.feng@gmail.com>
To: paulmck@kernel.org
Cc: linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org,
kernel-team@fb.com, mingo@kernel.org, stern@rowland.harvard.edu,
parri.andrea@gmail.com, will@kernel.org, peterz@infradead.org,
npiggin@gmail.com, dhowells@redhat.com, j.alglave@ucl.ac.uk,
luc.maranget@inria.fr, akiyks@gmail.com
Subject: Re: [PATCH memory-model 5/8] tools/memory-model: Add a glossary of LKMM terms
Date: Fri, 6 Nov 2020 09:47:22 +0800 [thread overview]
Message-ID: <20201106014722.GB3025@boqun-archlinux> (raw)
In-Reply-To: <20201105220017.15410-5-paulmck@kernel.org>
On Thu, Nov 05, 2020 at 02:00:14PM -0800, paulmck@kernel.org wrote:
> From: "Paul E. McKenney" <paulmck@kernel.org>
>
> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
> ---
> tools/memory-model/Documentation/glossary.txt | 155 ++++++++++++++++++++++++++
> 1 file changed, 155 insertions(+)
> create mode 100644 tools/memory-model/Documentation/glossary.txt
>
> diff --git a/tools/memory-model/Documentation/glossary.txt b/tools/memory-model/Documentation/glossary.txt
> new file mode 100644
> index 0000000..036fa28
> --- /dev/null
> +++ b/tools/memory-model/Documentation/glossary.txt
> @@ -0,0 +1,155 @@
> +This document contains brief definitions of LKMM-related terms. Like most
> +glossaries, it is not intended to be read front to back (except perhaps
> +as a way of confirming a diagnosis of OCD), but rather to be searched
> +for specific terms.
> +
> +
> +Address Dependency: When the address of a later memory access is computed
> + based on the value returned by an earlier load, an "address
> + dependency" extends from that load extending to the later access.
> + Address dependencies are quite common in RCU read-side critical
> + sections:
> +
> + 1 rcu_read_lock();
> + 2 p = rcu_dereference(gp);
> + 3 do_something(p->a);
> + 4 rcu_read_unlock();
> +
> + In this case, because the address of "p->a" on line 3 is computed
> + from the value returned by the rcu_dereference() on line 2, the
> + address dependency extends from that rcu_dereference() to that
> + "p->a". In rare cases, optimizing compilers can destroy address
> + dependencies. Please see Documentation/RCU/rcu_dereference.txt
> + for more information.
> +
> + See also "Control Dependency".
> +
> +Acquire: With respect to a lock, acquiring that lock, for example,
> + using spin_lock(). With respect to a non-lock shared variable,
> + a special operation that includes a load and which orders that
> + load before later memory references running on that same CPU.
> + An example special acquire operation is smp_load_acquire(),
> + but atomic_read_acquire() and atomic_xchg_acquire() also include
> + acquire loads.
> +
> + When an acquire load returns the value stored by a release store
> + to that same variable, then all operations preceding that store
Change this to:
When an acquire load reads-from a release store
, and put a reference to "Reads-from"? I think this makes the document
more consistent in that it makes clear "an acquire load returns the
value stored by a release store to the same variable" is not a special
case, it's simple a "Reads-from".
> + happen before any operations following that load acquire.
Add a reference to the definition of "happen before" in explanation.txt?
Regards,
Boqun
> +
> + See also "Relaxed" and "Release".
> +
[...]
next prev parent reply other threads:[~2020-11-06 1:47 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-05 21:59 [PATCH memory-model 0/8] LKMM updates for v5.11 Paul E. McKenney
2020-11-05 22:00 ` [PATCH memory-model 1/8] tools: memory-model: Document that the LKMM can easily miss control dependencies paulmck
2020-11-05 22:00 ` [PATCH memory-model 2/8] tools/memory-model: Move Documentation description to Documentation/README paulmck
2020-11-05 22:00 ` [PATCH memory-model 3/8] tools/memory-model: Document categories of ordering primitives paulmck
2020-11-06 16:56 ` Alan Stern
2020-11-06 19:11 ` Paul E. McKenney
2020-11-05 22:00 ` [PATCH memory-model 4/8] docs/memory-barriers.txt: Fix a typo in CPU MEMORY BARRIERS section paulmck
2020-11-05 22:00 ` [PATCH memory-model 5/8] tools/memory-model: Add a glossary of LKMM terms paulmck
2020-11-06 1:47 ` Boqun Feng [this message]
2020-11-06 18:01 ` Paul E. McKenney
2020-11-07 3:07 ` Boqun Feng
2020-11-06 16:59 ` Alan Stern
2020-11-06 18:04 ` Paul E. McKenney
2020-11-06 19:23 ` Alan Stern
2020-11-06 19:59 ` Paul E. McKenney
2020-11-06 20:40 ` Alan Stern
2020-11-06 21:04 ` Paul E. McKenney
2020-11-07 2:32 ` Alan Stern
2020-11-05 22:00 ` [PATCH memory-model 6/8] tools/memory-model: Add types to litmus tests paulmck
2020-11-05 22:41 ` Akira Yokosawa
2020-11-05 22:56 ` Paul E. McKenney
2020-11-25 11:34 ` Akira Yokosawa
2020-11-27 15:46 ` Paul E. McKenney
2020-11-28 5:56 ` Akira Yokosawa
2020-11-28 6:00 ` [PATCH 1/2] tools/memory-model: Remove redundant initialization in " Akira Yokosawa
2020-11-28 6:01 ` [PATCH 2/2] tools/memory-model: Fix typo in klitmus7 compatibility table Akira Yokosawa
2020-11-29 3:33 ` Paul E. McKenney
2020-11-05 22:00 ` [PATCH memory-model 7/8] tools/memory-model: Use "buf" and "flag" for message-passing tests paulmck
2020-11-05 22:00 ` [PATCH memory-model 8/8] tools/memory-model: Label MP tests' producers and consumers paulmck
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