From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752991AbbJFRVf (ORCPT ); Tue, 6 Oct 2015 13:21:35 -0400 Received: from relay3-d.mail.gandi.net ([217.70.183.195]:38035 "EHLO relay3-d.mail.gandi.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752769AbbJFRVe (ORCPT ); Tue, 6 Oct 2015 13:21:34 -0400 Date: Tue, 6 Oct 2015 10:21:28 -0700 From: Josh Triplett To: "Paul E. McKenney" Cc: linux-kernel@vger.kernel.org, mingo@kernel.org, jiangshanlai@gmail.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@efficios.com, tglx@linutronix.de, peterz@infradead.org, 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 10/13] rcu: Add rcu_pointer_handoff() Message-ID: <20151006172128.GE9600@cloud> References: <20151006161305.GA9799@linux.vnet.ibm.com> <1444148028-11551-1-git-send-email-paulmck@linux.vnet.ibm.com> <1444148028-11551-10-git-send-email-paulmck@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1444148028-11551-10-git-send-email-paulmck@linux.vnet.ibm.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Oct 06, 2015 at 09:13:45AM -0700, Paul E. McKenney wrote: > This commit adds an rcu_pointer_handoff() that is intended to mark > situations where a structure's protection transitions from RCU to some > other mechanism (locking, reference counting, whatever). These markings > should allow external tools to more easily spot bugs involving leaking > pointers out of RCU read-side critical sections. > > Signed-off-by: Paul E. McKenney Shouldn't this expect the __rcu address space on the pointer, and cast away the __rcu with __force? > include/linux/rcupdate.h | 22 ++++++++++++++++++++++ > 1 file changed, 22 insertions(+) > > diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h > index 6c3ceceb6148..587eb057e2fa 100644 > --- a/include/linux/rcupdate.h > +++ b/include/linux/rcupdate.h > @@ -813,6 +813,28 @@ static inline void rcu_preempt_sleep_check(void) > #define rcu_dereference_sched(p) rcu_dereference_sched_check(p, 0) > > /** > + * rcu_pointer_handoff() - Hand off a pointer from RCU to other mechanism > + * @p: The pointer to hand off > + * > + * This is simply an identity function, but it documents where a pointer > + * is handed off from RCU to some other synchronization mechanism, for > + * example, reference counting or locking. In C11, it would map to > + * kill_dependency(). It could be used as follows: > + * > + * rcu_read_lock(); > + * p = rcu_dereference(gp); > + * long_lived = is_long_lived(p); > + * if (long_lived) { > + * if (!atomic_inc_not_zero(p->refcnt)) > + * long_lived = false; > + * else > + * p = rcu_pointer_handoff(p); > + * } > + * rcu_read_unlock(); > + */ > +#define rcu_pointer_handoff(p) (p) > + > +/** > * rcu_read_lock() - mark the beginning of an RCU read-side critical section > * > * When synchronize_rcu() is invoked on one CPU while other CPUs > -- > 2.5.2 >