From: "Paul E. McKenney" <paulmck@kernel.org>
To: Andrea Parri <parri.andrea@gmail.com>
Cc: linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org,
kernel-team@meta.com, mingo@kernel.org,
stern@rowland.harvard.edu, will@kernel.org, peterz@infradead.org,
boqun.feng@gmail.com, npiggin@gmail.com, dhowells@redhat.com,
j.alglave@ucl.ac.uk, luc.maranget@inria.fr, akiyks@gmail.com,
Joel Fernandes <joel@joelfernandes.org>,
Andrea Parri <andrea.parri@amarulasolutions.com>,
Jonas Oberhauser <jonas.oberhauser@huawei.com>
Subject: Re: [PATCH memory-model 7/8] tools/memory-model: Add documentation about SRCU read-side critical sections
Date: Wed, 22 Mar 2023 11:02:17 -0700 [thread overview]
Message-ID: <ee922523-cc65-4254-b735-9e471c0e1c20@paulmck-laptop> (raw)
In-Reply-To: <ZBpcpPIq9k2mX7cw@andrea>
On Wed, Mar 22, 2023 at 02:40:52AM +0100, Andrea Parri wrote:
> On Mon, Mar 20, 2023 at 06:02:45PM -0700, Paul E. McKenney wrote:
> > From: Alan Stern <stern@rowland.harvard.edu>
> >
> > Expand the discussion of SRCU and its read-side critical sections in
> > the Linux Kernel Memory Model documentation file explanation.txt. The
> > new material discusses recent changes to the memory model made in
> > commit 6cd244c87428 ("tools/memory-model: Provide exact SRCU
> > semantics").
>
> How about squashing the diff below (adjusting subject and changelog):
Looks good to me, thank you!
Please submit an official patch with Joel's and Alan's tags and I
will be happy to pull it in.
Thanx, Paul
> Andrea
>
> diff --git a/tools/memory-model/Documentation/litmus-tests.txt b/tools/memory-model/Documentation/litmus-tests.txt
> index 26554b1c5575e..acac527328a1f 100644
> --- a/tools/memory-model/Documentation/litmus-tests.txt
> +++ b/tools/memory-model/Documentation/litmus-tests.txt
> @@ -1028,32 +1028,7 @@ Limitations of the Linux-kernel memory model (LKMM) include:
> additional call_rcu() process to the site of the
> emulated rcu-barrier().
>
> - e. Although sleepable RCU (SRCU) is now modeled, there
> - are some subtle differences between its semantics and
> - those in the Linux kernel. For example, the kernel
> - might interpret the following sequence as two partially
> - overlapping SRCU read-side critical sections:
> -
> - 1 r1 = srcu_read_lock(&my_srcu);
> - 2 do_something_1();
> - 3 r2 = srcu_read_lock(&my_srcu);
> - 4 do_something_2();
> - 5 srcu_read_unlock(&my_srcu, r1);
> - 6 do_something_3();
> - 7 srcu_read_unlock(&my_srcu, r2);
> -
> - In contrast, LKMM will interpret this as a nested pair of
> - SRCU read-side critical sections, with the outer critical
> - section spanning lines 1-7 and the inner critical section
> - spanning lines 3-5.
> -
> - This difference would be more of a concern had anyone
> - identified a reasonable use case for partially overlapping
> - SRCU read-side critical sections. For more information
> - on the trickiness of such overlapping, please see:
> - https://paulmck.livejournal.com/40593.html
> -
> - f. Reader-writer locking is not modeled. It can be
> + e. Reader-writer locking is not modeled. It can be
> emulated in litmus tests using atomic read-modify-write
> operations.
>
>
> Andrea
next prev parent reply other threads:[~2023-03-22 18:02 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-03-21 1:02 [PATCH memory-model 0/8] LKMM updates for v6.4 Paul E. McKenney
2023-03-21 1:02 ` [PATCH memory-model 1/8] tools/memory-model: Update some warning labels Paul E. McKenney
2023-03-22 0:51 ` Andrea Parri
2023-03-21 1:02 ` [PATCH memory-model 2/8] tools/memory-model: Unify UNLOCK+LOCK pairings to po-unlock-lock-po Paul E. McKenney
2023-03-22 0:59 ` Andrea Parri
2023-03-22 18:06 ` Paul E. McKenney
2023-03-21 1:02 ` [PATCH memory-model 3/8] tools/memory-model: Add smp_mb__after_srcu_read_unlock() Paul E. McKenney
2023-03-21 1:02 ` [PATCH memory-model 4/8] tools/memory-model: Restrict to-r to read-read address dependency Paul E. McKenney
2023-03-22 0:53 ` Andrea Parri
2023-03-21 1:02 ` [PATCH memory-model 5/8] tools/memory-model: Provide exact SRCU semantics Paul E. McKenney
2023-03-22 1:07 ` Andrea Parri
2023-03-22 1:13 ` Alan Stern
2023-03-21 1:02 ` [PATCH memory-model 6/8] tools/memory-model: Make ppo a subrelation of po Paul E. McKenney
2023-03-21 1:02 ` [PATCH memory-model 7/8] tools/memory-model: Add documentation about SRCU read-side critical sections Paul E. McKenney
2023-03-22 1:40 ` Andrea Parri
2023-03-22 2:17 ` Joel Fernandes
2023-03-22 14:30 ` Alan Stern
2023-03-22 18:02 ` Paul E. McKenney [this message]
2023-03-21 1:02 ` [PATCH memory-model 8/8] Documentation: litmus-tests: Correct spelling Paul E. McKenney
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