From: Boqun Feng <boqun.feng@gmail.com>
To: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
Andrew Morton <akpm@linux-foundation.org>,
Peter Zijlstra <peterz@infradead.org>,
linux-kernel@vger.kernel.org, Nicholas Piggin <npiggin@gmail.com>,
Michael Ellerman <mpe@ellerman.id.au>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
"Paul E. McKenney" <paulmck@kernel.org>,
Will Deacon <will@kernel.org>,
Alan Stern <stern@rowland.harvard.edu>,
John Stultz <jstultz@google.com>,
Neeraj Upadhyay <Neeraj.Upadhyay@amd.com>,
Frederic Weisbecker <frederic@kernel.org>,
Joel Fernandes <joel@joelfernandes.org>,
Josh Triplett <josh@joshtriplett.org>,
Uladzislau Rezki <urezki@gmail.com>,
Steven Rostedt <rostedt@goodmis.org>,
Lai Jiangshan <jiangshanlai@gmail.com>,
Zqiang <qiang.zhang1211@gmail.com>,
Ingo Molnar <mingo@redhat.com>, Waiman Long <longman@redhat.com>,
Mark Rutland <mark.rutland@arm.com>,
Thomas Gleixner <tglx@linutronix.de>,
Vlastimil Babka <vbabka@suse.cz>,
maged.michael@gmail.com, Mateusz Guzik <mjguzik@gmail.com>,
Jonas Oberhauser <jonas.oberhauser@huaweicloud.com>,
rcu@vger.kernel.org, linux-mm@kvack.org, lkmm@lists.linux.dev
Subject: Re: [RFC PATCH 3/4] hp: Implement Hazard Pointers
Date: Mon, 7 Oct 2024 06:47:31 -0700 [thread overview]
Message-ID: <ZwPmc_CXW15ilRaK@boqun-archlinux> (raw)
In-Reply-To: <bb890ea6-742f-40b7-ad3d-aa28f658fa3d@efficios.com>
On Thu, Oct 03, 2024 at 09:30:53AM -0400, Mathieu Desnoyers wrote:
[...]
> > > + /*
> > > + * Use RCU dereference without lockdep checks, because
> > > + * lockdep is not aware of HP guarantees.
> > > + */
> > > + addr2 = rcu_access_pointer(*addr_p); /* Load A */
> >
> > Why rcu_access_pointer() instead of READ_ONCE()? Because you want to
> > mark the head of address dependency?
>
> Yes, the intent here is to mark the address dependency and provide
> a publication guarantee similar to RCU pairing rcu_assign_pointer
> and rcu_dereference. Do you see any reason why READ_ONCE() would
> suffice here ?
READ_ONCE() also provides address dependencies. See the "DEPENDENCY
RELATIONS: data, addr, and ctrl" section in
tools/memory-model/Documentation/explanantion.txt.
Regards,
Boqun
>
> Thanks,
>
> Mathieu
>
next prev parent reply other threads:[~2024-10-07 13:48 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-10-02 1:02 [RFC PATCH 0/4] sched+mm: Track lazy active mm existence with hazard pointers Mathieu Desnoyers
2024-10-02 1:02 ` [RFC PATCH 1/4] compiler.h: Introduce ptr_eq() to preserve address dependency Mathieu Desnoyers
2024-10-03 0:08 ` Joel Fernandes
2024-10-03 14:19 ` Mathieu Desnoyers
2024-10-03 22:09 ` Joel Fernandes
2024-10-02 1:02 ` [RFC PATCH 2/4] Documentation: RCU: Refer to ptr_eq() Mathieu Desnoyers
2024-10-02 1:02 ` [RFC PATCH 3/4] hp: Implement Hazard Pointers Mathieu Desnoyers
2024-10-03 0:24 ` Boqun Feng
2024-10-03 13:30 ` Mathieu Desnoyers
2024-10-07 13:47 ` Boqun Feng [this message]
2024-10-07 14:52 ` Mathieu Desnoyers
2024-10-02 1:02 ` [RFC PATCH 4/4] sched+mm: Use hazard pointers to track lazy active mm existence Mathieu Desnoyers
2024-10-04 10:14 ` kernel test robot
2024-10-02 14:09 ` [RFC PATCH 0/4] sched+mm: Track lazy active mm existence with hazard pointers Paul E. McKenney
2024-10-02 15:26 ` Mathieu Desnoyers
2024-10-02 15:33 ` Matthew Wilcox
2024-10-02 15:36 ` Mathieu Desnoyers
2024-10-02 15:53 ` Mathieu Desnoyers
2024-10-02 15:58 ` Jens Axboe
2024-10-02 16:02 ` Mathieu Desnoyers
2024-10-02 16:14 ` Jens Axboe
2024-10-02 17:39 ` Linus Torvalds
2024-10-05 16:15 ` Peter Zijlstra
2024-10-05 16:56 ` Linus Torvalds
2024-10-07 7:06 ` Peter Zijlstra
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