From: Peter Zijlstra <peterz@infradead.org>
To: "Paul E. McKenney" <paulmck@kernel.org>
Cc: Steven Rostedt <rostedt@goodmis.org>,
David Howells <dhowells@redhat.com>,
rcu@vger.kernel.org, linux-kernel@vger.kernel.org,
mingo@kernel.org, jiangshanlai@gmail.com, dipankar@in.ibm.com,
akpm@linux-foundation.org, mathieu.desnoyers@efficios.com,
josh@joshtriplett.org, tglx@linutronix.de, edumazet@google.com,
fweisbec@gmail.com, oleg@redhat.com, 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 15:41:31 +0200 [thread overview]
Message-ID: <20191003134131.GS4536@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20191003133315.GN2689@paulmck-ThinkPad-P72>
On Thu, Oct 03, 2019 at 06:33:15AM -0700, Paul E. McKenney wrote:
> On Thu, Oct 03, 2019 at 09:08:50AM -0400, Steven Rostedt 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?
>
> Historically, xchg() has been quite a bit slower than a pair of assignment
> statements, in part due to the strong memory ordering guaranteed by
> xchg(). Has that changed? If so, then, agreed, it might make sense to
> use xchg().
Nope, still the case. xchg() is an atomic op with full ordering.
next prev parent reply other threads:[~2019-10-03 13:42 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 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 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
2019-10-03 8:38 ` [PATCH tip/core/rcu 5/9] fs/afs: " David Howells
2019-10-05 16:10 ` Paul E. McKenney
2019-10-03 8:39 ` [PATCH tip/core/rcu 1/9] rcu: Upgrade rcu_swap_protected() to rcu_replace() David Howells
2019-10-03 13:08 ` Steven Rostedt
2019-10-03 13:33 ` Paul E. McKenney
2019-10-03 13:41 ` Peter Zijlstra [this message]
2019-10-03 13:58 ` Paul E. McKenney
2019-10-03 14:01 ` Joel Fernandes
2019-10-03 16:31 ` Mathieu Desnoyers
2019-10-03 18:05 ` Peter Zijlstra
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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