From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757271AbbCCQh6 (ORCPT ); Tue, 3 Mar 2015 11:37:58 -0500 Received: from e36.co.us.ibm.com ([32.97.110.154]:37158 "EHLO e36.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757168AbbCCQhv (ORCPT ); Tue, 3 Mar 2015 11:37:51 -0500 From: "Paul E. McKenney" To: linux-kernel@vger.kernel.org Cc: 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, 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 3/6] documentation: Update NO_HZ_FULL interaction with POSIX timers Date: Tue, 3 Mar 2015 08:37:37 -0800 Message-Id: <1425400660-6380-3-git-send-email-paulmck@linux.vnet.ibm.com> X-Mailer: git-send-email 1.8.1.5 In-Reply-To: <1425400660-6380-1-git-send-email-paulmck@linux.vnet.ibm.com> References: <20150303163714.GA5427@linux.vnet.ibm.com> <1425400660-6380-1-git-send-email-paulmck@linux.vnet.ibm.com> X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 15030316-0021-0000-0000-000008FB3712 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: "Paul E. McKenney" POSIX timers are no longer starved on adaptive-ticks CPUs. Instead, they prevent affected CPUs from entering adaptive-ticks mode. This commit therefore updates the NO_HZ.txt documentation. Signed-off-by: Paul E. McKenney --- Documentation/timers/NO_HZ.txt | 10 +++------- 1 file changed, 3 insertions(+), 7 deletions(-) diff --git a/Documentation/timers/NO_HZ.txt b/Documentation/timers/NO_HZ.txt index cca122f25120..6eaf576294f3 100644 --- a/Documentation/timers/NO_HZ.txt +++ b/Documentation/timers/NO_HZ.txt @@ -158,13 +158,9 @@ not come for free: to the need to inform kernel subsystems (such as RCU) about the change in mode. -3. POSIX CPU timers on adaptive-tick CPUs may miss their deadlines - (perhaps indefinitely) because they currently rely on - scheduling-tick interrupts. This will likely be fixed in - one of two ways: (1) Prevent CPUs with POSIX CPU timers from - entering adaptive-tick mode, or (2) Use hrtimers or other - adaptive-ticks-immune mechanism to cause the POSIX CPU timer to - fire properly. +3. POSIX CPU timers prevent CPUs from entering adaptive-tick mode. + Real-time applications needing to take actions based on CPU time + consumption need to use other means of doing so. 4. If there are more perf events pending than the hardware can accommodate, they are normally round-robined so as to collect -- 1.8.1.5