From: Alan Stern <stern@rowland.harvard.edu>
To: "Paul E. McKenney" <paulmck@kernel.org>
Cc: Jonas Oberhauser <jonas.oberhauser@huaweicloud.com>,
Andrea Parri <parri.andrea@gmail.com>,
Jonas Oberhauser <jonas.oberhauser@huawei.com>,
Peter Zijlstra <peterz@infradead.org>, will <will@kernel.org>,
"boqun.feng" <boqun.feng@gmail.com>, npiggin <npiggin@gmail.com>,
dhowells <dhowells@redhat.com>, "j.alglave" <j.alglave@ucl.ac.uk>,
"luc.maranget" <luc.maranget@inria.fr>, akiyks <akiyks@gmail.com>,
dlustig <dlustig@nvidia.com>, joel <joel@joelfernandes.org>,
urezki <urezki@gmail.com>,
quic_neeraju <quic_neeraju@quicinc.com>,
frederic <frederic@kernel.org>,
Kernel development list <linux-kernel@vger.kernel.org>
Subject: Re: [Patch 2/2] tools/memory-model: Provide exact SRCU semantics
Date: Thu, 26 Jan 2023 14:10:10 -0500 [thread overview]
Message-ID: <Y9LQEuUBn3fwZEBe@rowland.harvard.edu> (raw)
In-Reply-To: <20230126173507.GE2948950@paulmck-ThinkPad-P17-Gen-1>
On Thu, Jan 26, 2023 at 09:35:07AM -0800, Paul E. McKenney wrote:
> On Thu, Jan 26, 2023 at 12:30:14PM +0100, Jonas Oberhauser wrote:
> > I don't think they're necessarily implemented in a compatible way, so
> >
> > r = srcu_lock(s);
> > srcu_up(s,r);
> >
> > might not actually work, but would currently be ok'ed by LKMM.
>
> In kernels built with CONFIG_PROVE_LOCKING=y (AKA built with lockdep
> enabled), lockdep would complain about having an srcu_read_lock() with
> no matching srcu_read_unlock(). Kernels built without lockdep (that is,
> kernels actually used in production) would be happy with this.
>
> So as Jonas suspects, this should be classified as not actually working.
Lockdep complaints don't actually stop things from working (unless you
want them to). They're just warnings, right?
Alan
next prev parent reply other threads:[~2023-01-26 19:10 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-01-25 20:19 [PATCH 0/2] SRCU changes for the Linux Kernel Memory Model Alan Stern
2023-01-25 20:20 ` [Patch 1/2] tools/memory-model: Update some warning labels Alan Stern
2023-01-25 20:21 ` [Patch 2/2] tools/memory-model: Provide exact SRCU semantics Alan Stern
2023-01-25 21:04 ` Jonas Oberhauser
2023-01-25 21:58 ` Paul E. McKenney
2023-01-25 22:52 ` Alan Stern
2023-01-26 11:30 ` Jonas Oberhauser
2023-01-26 16:02 ` Alan Stern
2023-01-26 16:31 ` Jonas Oberhauser
2023-01-26 17:35 ` Paul E. McKenney
2023-01-26 19:10 ` Alan Stern [this message]
2023-01-26 19:31 ` Paul E. McKenney
2023-02-01 10:31 ` Jonas Oberhauser
2023-01-25 20:35 ` [Patch 1/2] tools/memory-model: Update some warning labels Jonas Oberhauser
2023-01-25 22:01 ` Paul E. McKenney
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