From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: Peter Zijlstra <peterz@infradead.org>
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 9/9] rcu: Provide counterpart to rcu_dereference() for non-RCU situations
Date: Wed, 29 Oct 2014 05:42:03 -0700 [thread overview]
Message-ID: <20141029124203.GK5718@linux.vnet.ibm.com> (raw)
In-Reply-To: <20141029105704.GY3337@twins.programming.kicks-ass.net>
On Wed, Oct 29, 2014 at 11:57:04AM +0100, Peter Zijlstra wrote:
> On Tue, Oct 28, 2014 at 03:10:02PM -0700, Paul E. McKenney wrote:
> > From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
> >
> > Although rcu_dereference() and friends can be used in situations where
> > object lifetimes are being managed by something other than RCU, the
> > resulting sparse and lockdep-RCU noise can be annoying. This commit
> > therefore supplies a lockless_dereference(), which provides the
> > protection for dereferences without the RCU-related debugging noise.
> >
> > Reported-by: Al Viro <viro@ZenIV.linux.org.uk>
> > Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
> > ---
>
> > +#define lockless_dereference(p) \
> > +({ \
> > + typeof(p) _________p1 = ACCESS_ONCE(p); \
> > + smp_read_barrier_depends(); /* Dependency order vs. p above. */ \
> > + (_________p1); \
> > +})
>
> Should we not have at least a single user along with this?
And we do. In fact, Al Viro has pulled this into his vfs.git tree and
so I will be dropping this patch in favor of his.
Thanx, Paul
next prev parent reply other threads:[~2014-10-29 12:42 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-10-28 22:09 [PATCH tip/core/rcu 0/9] Miscellaneous fixes for 3.19 Paul E. McKenney
2014-10-28 22:09 ` [PATCH tip/core/rcu 1/9] rcu: Remove CONFIG_RCU_CPU_STALL_VERBOSE Paul E. McKenney
2014-10-28 22:09 ` [PATCH tip/core/rcu 2/9] compiler: Allow 1- and 2-byte smp_load_acquire() and smp_store_release() Paul E. McKenney
2014-10-28 22:09 ` [PATCH tip/core/rcu 3/9] drivers/md: Use rcu_dereference() for accessing rcu pointer Paul E. McKenney
2014-11-21 13:31 ` Kirill A. Shutemov
2014-11-21 14:30 ` Pranith Kumar
2014-11-21 14:58 ` Kirill A. Shutemov
2014-11-23 12:21 ` Pranith Kumar
2014-11-23 16:39 ` Eric Dumazet
2014-11-23 16:40 ` [PATCH ] drivers/md: use proper rcu accessor Eric Dumazet
2014-11-23 16:53 ` Mike Snitzer
2014-11-23 17:31 ` Eric Dumazet
2014-11-23 19:12 ` Mike Snitzer
2014-11-23 17:34 ` [PATCH v2] " Eric Dumazet
2014-11-24 4:09 ` Mike Snitzer
2014-10-28 22:09 ` [PATCH tip/core/rcu 4/9] dm: sparse: Annotate field with __rcu for checking Paul E. McKenney
2014-10-28 22:09 ` [PATCH tip/core/rcu 5/9] rcu: Add sparse check for RCU_INIT_POINTER() Paul E. McKenney
2014-10-28 22:09 ` [PATCH tip/core/rcu 6/9] rcu: Optimize cond_resched_rcu_qs() Paul E. McKenney
2014-10-28 22:10 ` [PATCH tip/core/rcu 7/9] rcu: More info about potential deadlocks with rcu_read_unlock() Paul E. McKenney
2014-10-28 22:10 ` [PATCH tip/core/rcu 8/9] rcu: Fix FIXME in rcu_tasks_kthread() Paul E. McKenney
2014-10-28 22:10 ` [PATCH tip/core/rcu 9/9] rcu: Provide counterpart to rcu_dereference() for non-RCU situations Paul E. McKenney
2014-10-29 10:57 ` Peter Zijlstra
2014-10-29 12:42 ` Paul E. McKenney [this message]
2014-10-29 19:15 ` Oleg Nesterov
2014-10-29 18:43 ` Paul E. McKenney
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