From: Peter Zijlstra <peterz@infradead.org>
To: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: linux-kernel@vger.kernel.org, mingo@kernel.org,
laijs@cn.fujitsu.com, dipankar@in.ibm.com,
akpm@linux-foundation.org, mathieu.desnoyers@efficios.com,
josh@joshtriplett.org, tglx@linutronix.de, rostedt@goodmis.org,
dhowells@redhat.com, edumazet@google.com, dvhart@linux.intel.com,
fweisbec@gmail.com, oleg@redhat.com, bobby.prani@gmail.com
Subject: Re: [PATCH tip/core/rcu 01/14] rcu: Protect rcu_boost() lockless accesses with ACCESS_ONCE()
Date: Thu, 8 Jan 2015 10:41:02 +0100 [thread overview]
Message-ID: <20150108094102.GD29390@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <1420651953-2651-1-git-send-email-paulmck@linux.vnet.ibm.com>
On Wed, Jan 07, 2015 at 09:32:20AM -0800, Paul E. McKenney wrote:
> From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
>
> This commit prevents random compiler optimizations by applying
> ACCESS_ONCE() to lockless accesses.
>
> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
> ---
> kernel/rcu/tree_plugin.h | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
> index 3ec85cb5d544..d59913ef8360 100644
> --- a/kernel/rcu/tree_plugin.h
> +++ b/kernel/rcu/tree_plugin.h
> @@ -1127,7 +1127,8 @@ static int rcu_boost(struct rcu_node *rnp)
> struct task_struct *t;
> struct list_head *tb;
>
> - if (rnp->exp_tasks == NULL && rnp->boost_tasks == NULL)
> + if (ACCESS_ONCE(rnp->exp_tasks) == NULL &&
> + ACCESS_ONCE(rnp->boost_tasks) == NULL)
> return 0; /* Nothing left to boost. */
Didn't we just obsolete ACCESS_ONCE with that {READ,WRITE}_ONCE stuff?
next prev parent reply other threads:[~2015-01-08 9:41 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-01-07 17:32 [PATCH tip/core/rcu 0/14] Preemptible-RCU updates for 3.20 Paul E. McKenney
2015-01-07 17:32 ` [PATCH tip/core/rcu 01/14] rcu: Protect rcu_boost() lockless accesses with ACCESS_ONCE() Paul E. McKenney
2015-01-07 17:32 ` [PATCH tip/core/rcu 02/14] rcu: Rename "empty" to "empty_norm" in preparation for boost rework Paul E. McKenney
2015-01-07 17:32 ` [PATCH tip/core/rcu 03/14] rcu: Abstract rcu_cleanup_dead_rnp() from rcu_cleanup_dead_cpu() Paul E. McKenney
2015-01-07 17:32 ` [PATCH tip/core/rcu 04/14] rcu: Make rcu_read_unlock_special() propagate ->qsmaskinit bit clearing Paul E. McKenney
2015-01-07 17:32 ` [PATCH tip/core/rcu 05/14] rcu: Don't migrate blocked tasks even if all corresponding CPUs offline Paul E. McKenney
2015-01-07 17:32 ` [PATCH tip/core/rcu 06/14] rcu: Shorten irq-disable region in rcu_cleanup_dead_cpu() Paul E. McKenney
2015-01-07 17:32 ` [PATCH tip/core/rcu 07/14] rcu: Make use of rcu_preempt_has_tasks() Paul E. McKenney
2015-01-07 17:32 ` [PATCH tip/core/rcu 08/14] rcu: Don't spawn rcub kthreads on root rcu_node structure Paul E. McKenney
2015-01-07 17:32 ` [PATCH tip/core/rcu 09/14] rcu: Don't initiate RCU priority boosting on root rcu_node Paul E. McKenney
2015-01-07 17:32 ` [PATCH tip/core/rcu 10/14] rcu: Don't bother affinitying rcub kthreads away from offline CPUs Paul E. McKenney
2015-01-07 17:32 ` [PATCH tip/core/rcu 11/14] rcu: Note quiescent state when CPU goes offline Paul E. McKenney
2015-01-07 17:32 ` [PATCH tip/core/rcu 12/14] rcu: Revert "Allow post-unlock reference for rt_mutex" to avoid priority-inversion Paul E. McKenney
2015-01-07 17:32 ` [PATCH tip/core/rcu 13/14] rcu: Don't scan root rcu_node structure for stalled tasks Paul E. McKenney
2015-01-07 17:32 ` [PATCH tip/core/rcu 14/14] rcu: Remove redundant callback-list initialization Paul E. McKenney
2015-01-08 9:41 ` Peter Zijlstra [this message]
2015-01-08 15:22 ` [PATCH tip/core/rcu 01/14] rcu: Protect rcu_boost() lockless accesses with ACCESS_ONCE() Paul E. McKenney
2015-01-09 6:41 ` Davidlohr Bueso
2015-01-09 13:49 ` Paul E. McKenney
2015-01-09 13:56 ` Peter Zijlstra
2015-01-09 14:07 ` Paul E. McKenney
2015-01-09 16:53 ` Mathieu Desnoyers
2015-01-09 21:58 ` Christian Borntraeger
2015-01-10 0:27 ` Davidlohr Bueso
2015-01-12 8:59 ` Peter Zijlstra
2015-01-12 22:12 ` Paul E. McKenney
2015-01-13 8:18 ` Christian Borntraeger
2015-01-13 9:29 ` Peter Zijlstra
2015-01-13 17:47 ` Paul E. McKenney
2015-01-13 19:12 ` Davidlohr Bueso
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