From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753167AbbJFQRd (ORCPT ); Tue, 6 Oct 2015 12:17:33 -0400 Received: from e32.co.us.ibm.com ([32.97.110.150]:40382 "EHLO e32.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752705AbbJFQN6 (ORCPT ); Tue, 6 Oct 2015 12:13:58 -0400 X-IBM-Helo: d03dlp03.boulder.ibm.com X-IBM-MailFrom: paulmck@linux.vnet.ibm.com X-IBM-RcptTo: linux-kernel@vger.kernel.org From: "Paul E. McKenney" To: linux-kernel@vger.kernel.org Cc: mingo@kernel.org, jiangshanlai@gmail.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@efficios.com, josh@joshtriplett.org, 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, "Paul E. McKenney" Subject: [PATCH tip/core/rcu 10/13] rcu: Add rcu_pointer_handoff() Date: Tue, 6 Oct 2015 09:13:45 -0700 Message-Id: <1444148028-11551-10-git-send-email-paulmck@linux.vnet.ibm.com> X-Mailer: git-send-email 2.5.2 In-Reply-To: <1444148028-11551-1-git-send-email-paulmck@linux.vnet.ibm.com> References: <20151006161305.GA9799@linux.vnet.ibm.com> <1444148028-11551-1-git-send-email-paulmck@linux.vnet.ibm.com> X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 15100616-0005-0000-0000-000018BC7ECC Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 --- 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