From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757197AbcBXFIn (ORCPT ); Wed, 24 Feb 2016 00:08:43 -0500 Received: from e31.co.us.ibm.com ([32.97.110.149]:35505 "EHLO e31.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752580AbcBXFHq (ORCPT ); Wed, 24 Feb 2016 00:07:46 -0500 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 05/14] documentation: Remove obsolete reference to RCU-protected indexes Date: Tue, 23 Feb 2016 21:00:38 -0800 Message-Id: <1456290047-16654-5-git-send-email-paulmck@linux.vnet.ibm.com> X-Mailer: git-send-email 2.5.2 In-Reply-To: <20160224050021.GA14616@linux.vnet.ibm.com> References: <20160224050021.GA14616@linux.vnet.ibm.com> X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 16022405-8236-0000-0000-000016678F76 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit #1ebee8017d84 (rcu: Eliminate array-index-based RCU primitives) eliminated the primitives supporting RCU-protected array indexes, but failed to update Documentation/memory-barriers.txt accordingly. This commit therefore removes the discussion of RCU-protected array indexes. Signed-off-by: Paul E. McKenney --- Documentation/memory-barriers.txt | 15 --------------- 1 file changed, 15 deletions(-) diff --git a/Documentation/memory-barriers.txt b/Documentation/memory-barriers.txt index c90922b9b294..6bee0a2c43ab 100644 --- a/Documentation/memory-barriers.txt +++ b/Documentation/memory-barriers.txt @@ -565,21 +565,6 @@ odd-numbered bank is idle, one can see the new value of the pointer P (&B), but the old value of the variable B (2). -Another example of where data dependency barriers might be required is where a -number is read from memory and then used to calculate the index for an array -access: - - CPU 1 CPU 2 - =============== =============== - { M[0] == 1, M[1] == 2, M[3] = 3, P == 0, Q == 3 } - M[1] = 4; - - WRITE_ONCE(P, 1); - Q = READ_ONCE(P); - - D = M[Q]; - - The data dependency barrier is very important to the RCU system, for example. See rcu_assign_pointer() and rcu_dereference() in include/linux/rcupdate.h. This permits the current target of an RCU'd -- 2.5.2