From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965322AbcDLPST (ORCPT ); Tue, 12 Apr 2016 11:18:19 -0400 Received: from e37.co.us.ibm.com ([32.97.110.158]:39589 "EHLO e37.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S964978AbcDLPSJ (ORCPT ); Tue, 12 Apr 2016 11:18:09 -0400 X-IBM-Helo: d03dlp02.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 08/10] documentation: Sharpen up the no-readers quick quiz Date: Tue, 12 Apr 2016 08:18:19 -0700 Message-Id: <1460474301-22998-8-git-send-email-paulmck@linux.vnet.ibm.com> X-Mailer: git-send-email 2.5.2 In-Reply-To: <20160412151755.GA22416@linux.vnet.ibm.com> References: <20160412151755.GA22416@linux.vnet.ibm.com> X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 16041215-0025-0000-0000-00002CD84DF2 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Signed-off-by: Paul E. McKenney --- Documentation/RCU/Design/Requirements/Requirements.html | 13 ++++++++----- 1 file changed, 8 insertions(+), 5 deletions(-) diff --git a/Documentation/RCU/Design/Requirements/Requirements.html b/Documentation/RCU/Design/Requirements/Requirements.html index acdad96f78e9..85cf2238fd08 100644 --- a/Documentation/RCU/Design/Requirements/Requirements.html +++ b/Documentation/RCU/Design/Requirements/Requirements.html @@ -1002,18 +1002,21 @@ obligation to wait for these new readers.   Quick Quiz: - Suppose that synchronize_rcu() did wait until all readers had completed. - Would the updater be able to rely on this? + Suppose that synchronize_rcu() did wait until all + readers had completed instead of waiting only on + pre-existing readers. + For how long would the updater be able to rely on there + being no readers? Answer: - No. + For no time at all. Even if synchronize_rcu() were to wait until all readers had completed, a new reader might start immediately after synchronize_rcu() completed. Therefore, the code following - synchronize_rcu() cannot rely on there being no readers - in any case. + synchronize_rcu() can never rely on there being + no readers.   -- 2.5.2