From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
To: rostedt <rostedt@goodmis.org>
Cc: David Howells <dhowells@redhat.com>,
paulmck@kernel.org, rcu <rcu@vger.kernel.org>,
linux-kernel <linux-kernel@vger.kernel.org>,
Ingo Molnar <mingo@kernel.org>,
Lai Jiangshan <jiangshanlai@gmail.com>,
dipankar <dipankar@in.ibm.com>,
Andrew Morton <akpm@linux-foundation.org>,
Josh Triplett <josh@joshtriplett.org>,
Thomas Gleixner <tglx@linutronix.de>,
Peter Zijlstra <peterz@infradead.org>,
Eric Dumazet <edumazet@google.com>, fweisbec <fweisbec@gmail.com>,
Oleg Nesterov <oleg@redhat.com>,
"Joel Fernandes, Google" <joel@joelfernandes.org>,
Bart Van Assche <bart.vanassche@wdc.com>,
Christoph Hellwig <hch@lst.de>, Hannes Reinecke <hare@suse.de>,
Johannes Thumshirn <jthumshirn@suse.de>,
Shane M Seymour <shane.seymour@hpe.com>,
"Martin K . Petersen" <martin.petersen@oracle.com>
Subject: Re: [PATCH tip/core/rcu 1/9] rcu: Upgrade rcu_swap_protected() to rcu_replace()
Date: Thu, 3 Oct 2019 12:31:38 -0400 (EDT) [thread overview]
Message-ID: <561448323.948.1570120298211.JavaMail.zimbra@efficios.com> (raw)
In-Reply-To: <20191003090850.1e2561b3@gandalf.local.home>
----- On Oct 3, 2019, at 9:08 AM, rostedt rostedt@goodmis.org wrote:
> On Thu, 03 Oct 2019 09:39:17 +0100
> David Howells <dhowells@redhat.com> wrote:
>
>> paulmck@kernel.org wrote:
>>
>> > +#define rcu_replace(rcu_ptr, ptr, c) \
>> > +({ \
>> > + typeof(ptr) __tmp = rcu_dereference_protected((rcu_ptr), (c)); \
>> > + rcu_assign_pointer((rcu_ptr), (ptr)); \
>> > + __tmp; \
>> > +})
>>
>> Does it make sense to actually use xchg() if that's supported by the arch?
>>
>
> Hmm, is there really any arch that doesn't support xchg()? It would be
> very hard to do any kind of atomic operations without it.
>
> cmpxchg() is the one that I understand is optional by the arch.
I remember going through all kernel arch headers myself and introduce
irq-off-based xchg and cmpxchg generic implementations for all UP
architectures lacking cmpxchg/xchg instructions.
We might want to consider simply using xchg() here.
FWIW, the API exposed by the Userspace RCU project (liburcu) for this
is:
rcu_xchg_pointer()
Thanks,
Mathieu
--
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com
next prev parent reply other threads:[~2019-10-03 17:11 UTC|newest]
Thread overview: 54+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-03 1:41 [PATCH tip/core/rcu 0/9] Replace rcu_swap_protected() for v5.5 Paul E. McKenney
2019-10-03 1:43 ` [PATCH tip/core/rcu 1/9] rcu: Upgrade rcu_swap_protected() to rcu_replace() paulmck
2019-10-03 8:39 ` David Howells
2019-10-03 13:08 ` Steven Rostedt
2019-10-03 13:33 ` Paul E. McKenney
2019-10-03 13:41 ` Peter Zijlstra
2019-10-03 13:58 ` Paul E. McKenney
2019-10-03 14:01 ` Joel Fernandes
2019-10-03 16:31 ` Mathieu Desnoyers [this message]
2019-10-03 18:05 ` Peter Zijlstra
2019-10-03 16:35 ` Mathieu Desnoyers
2019-10-03 16:52 ` Paul E. McKenney
2019-10-03 17:21 ` Mathieu Desnoyers
2019-10-03 19:09 ` Paul E. McKenney
2019-10-03 19:14 ` Mathieu Desnoyers
2019-10-03 1:43 ` [PATCH tip/core/rcu 2/9] x86/kvm/pmu: Replace rcu_swap_protected() with rcu_replace() paulmck
2019-10-03 10:14 ` Paolo Bonzini
2019-10-05 16:11 ` Paul E. McKenney
2019-10-03 1:43 ` [PATCH tip/core/rcu 3/9] drivers/gpu: " paulmck
2019-10-03 1:43 ` [PATCH tip/core/rcu 4/9] drivers/scsi: " paulmck
2019-10-04 2:09 ` Martin K. Petersen
2019-10-05 16:06 ` Paul E. McKenney
2019-10-10 2:36 ` Martin K. Petersen
2019-10-03 1:43 ` [PATCH tip/core/rcu 5/9] fs/afs: " paulmck
2019-10-03 8:38 ` David Howells
2019-10-05 16:10 ` Paul E. McKenney
2019-10-03 1:43 ` [PATCH tip/core/rcu 6/9] bpf/cgroup: " paulmck
2019-10-03 17:21 ` Andrii Nakryiko
2019-10-03 20:58 ` Song Liu
2019-10-05 16:11 ` Paul E. McKenney
2019-10-03 1:43 ` [PATCH tip/core/rcu 7/9] net/core: " paulmck
2019-10-03 1:43 ` [PATCH tip/core/rcu 8/9] net/netfilter: " paulmck
2019-10-08 14:16 ` Pablo Neira Ayuso
2019-10-09 15:36 ` Paul E. McKenney
2019-10-03 1:43 ` [PATCH tip/core/rcu 9/9] net/sched: " paulmck
2019-10-22 19:11 ` [PATCH v2 tip/core/rcu 0/10] Replace rcu_swap_protected() for v5.5 Paul E. McKenney
2019-10-22 19:12 ` [PATCH tip/core/rcu 01/10] rcu: Upgrade rcu_swap_protected() to rcu_replace() paulmck
2019-10-22 19:12 ` [PATCH tip/core/rcu 02/10] x86/kvm/pmu: Replace rcu_swap_protected() with rcu_replace() paulmck
2019-10-22 19:12 ` [PATCH tip/core/rcu 03/10] drivers/gpu: " paulmck
2019-10-22 19:12 ` paulmck
2019-10-28 12:57 ` Joonas Lahtinen
2019-10-28 12:57 ` [Intel-gfx] " Joonas Lahtinen
2019-10-28 12:57 ` Joonas Lahtinen
2019-10-28 12:57 ` Joonas Lahtinen
2019-10-28 13:40 ` Paul E. McKenney
2019-10-28 13:40 ` [Intel-gfx] " Paul E. McKenney
2019-10-28 13:40 ` Paul E. McKenney
2019-10-22 19:12 ` [PATCH tip/core/rcu 04/10] drivers/scsi: " paulmck
2019-10-22 19:12 ` [PATCH tip/core/rcu 05/10] fs/afs: " paulmck
2019-10-22 19:12 ` [PATCH tip/core/rcu 06/10] bpf/cgroup: " paulmck
2019-10-22 19:12 ` [PATCH tip/core/rcu 07/10] net/core: " paulmck
2019-10-22 19:12 ` [PATCH tip/core/rcu 08/10] net/netfilter: " paulmck
2019-10-22 19:12 ` [PATCH tip/core/rcu 09/10] net/sched: " paulmck
2019-10-22 19:12 ` [PATCH tip/core/rcu 10/10] security/safesetid: " paulmck
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