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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Mon, 25 Jun 2018 00:06:40 -0400 Received: from b01ledav003.gho.pok.ibm.com (b01ledav003.gho.pok.ibm.com [9.57.199.108]) by b01cxnp22036.gho.pok.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id w5P46deZ66453748 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL); Mon, 25 Jun 2018 04:06:39 GMT Received: from b01ledav003.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 3604AB2065; Mon, 25 Jun 2018 00:06:35 -0400 (EDT) Received: from b01ledav003.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 1409EB2064; Mon, 25 Jun 2018 00:06:35 -0400 (EDT) Received: from paulmck-ThinkPad-W541 (unknown [9.85.148.28]) by b01ledav003.gho.pok.ibm.com (Postfix) with ESMTP; Mon, 25 Jun 2018 00:06:35 -0400 (EDT) Received: by paulmck-ThinkPad-W541 (Postfix, from userid 1000) id 474A016C4004; Sun, 24 Jun 2018 21:08:44 -0700 (PDT) Date: Sun, 24 Jun 2018 21:08:44 -0700 From: "Paul E. McKenney" To: Joel Fernandes Cc: linux-kernel@vger.kernel.org, Jonathan Corbet , Josh Triplett , Lai Jiangshan , linux-doc@vger.kernel.org, Mathieu Desnoyers , Steven Rostedt , byungchul.park@lge.com Subject: Re: [RFC] doc: Improve rcu_dynticks::dynticks documentation Reply-To: paulmck@linux.vnet.ibm.com References: <20180624193451.250855-1-joel@joelfernandes.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180624193451.250855-1-joel@joelfernandes.org> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-GCONF: 00 x-cbid: 18062504-2213-0000-0000-000002BF7C7A X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00009251; HX=3.00000241; KW=3.00000007; PH=3.00000004; SC=3.00000265; SDB=6.01051935; UDB=6.00539227; IPR=6.00829908; MB=3.00021843; MTD=3.00000008; XFM=3.00000015; UTC=2018-06-25 04:06:43 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 18062504-2214-0000-0000-00005A992719 Message-Id: <20180625040844.GL3593@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2018-06-25_01:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1806210000 definitions=main-1806250047 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Jun 24, 2018 at 12:34:51PM -0700, Joel Fernandes wrote: > From: "Joel Fernandes (Google)" > > The very useful RCU Data-Structures describes that the dynticks counter > of the rcu_dynticks data structure is incremented when we transitions to > or from dynticks-idle mode. However it doesn't mention that it is also > incremented due to transitions to and from user mode which for dynticks > purposes is an extended quiescent state. > > I found this with tracing calls to rcu_dynticks_eqs_enter which can also > happen from rcu_user_enter. Lets add this information to the > Data-Structures document. > > Signed-off-by: Joel Fernandes (Google) Good addition, queued, thank you! Thanx, Paul > --- > .../RCU/Design/Data-Structures/Data-Structures.html | 8 +++++--- > 1 file changed, 5 insertions(+), 3 deletions(-) > > diff --git a/Documentation/RCU/Design/Data-Structures/Data-Structures.html b/Documentation/RCU/Design/Data-Structures/Data-Structures.html > index f5120a00f511..50be87e59937 100644 > --- a/Documentation/RCU/Design/Data-Structures/Data-Structures.html > +++ b/Documentation/RCU/Design/Data-Structures/Data-Structures.html > @@ -1227,9 +1227,11 @@ to overflow the counter, this approach corrects the > CPU enters the idle loop from process context. > >

The ->dynticks field counts the corresponding > -CPU's transitions to and from dyntick-idle mode, so that this counter > -has an even value when the CPU is in dyntick-idle mode and an odd > -value otherwise. > +CPU's transitions to and from either dyntick-idle or user mode, so > +that this counter has an even value when the CPU is in dyntick-idle > +mode or user mode and an odd value otherwise. The transitions to/from > +user mode need to be counted for user mode adaptive-ticks support > +(see timers/NO_HZ.txt). > >

The ->rcu_need_heavy_qs field is used > to record the fact that the RCU core code would really like to > -- > 2.18.0.rc2.346.g013aa6912e-goog >