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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Thu, 4 Apr 2019 22:07:57 +0100 Received: from b01ledav003.gho.pok.ibm.com (b01ledav003.gho.pok.ibm.com [9.57.199.108]) by b01cxnp23034.gho.pok.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id x34L7uAA19595392 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 4 Apr 2019 21:07:56 GMT Received: from b01ledav003.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 1C4B2B2064; Thu, 4 Apr 2019 21:07:56 +0000 (GMT) Received: from b01ledav003.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id E2D3FB205F; Thu, 4 Apr 2019 21:07:55 +0000 (GMT) Received: from paulmck-ThinkPad-W541 (unknown [9.70.82.188]) by b01ledav003.gho.pok.ibm.com (Postfix) with ESMTP; Thu, 4 Apr 2019 21:07:55 +0000 (GMT) Received: by paulmck-ThinkPad-W541 (Postfix, from userid 1000) id D9FD616C5F74; Thu, 4 Apr 2019 14:07:57 -0700 (PDT) Date: Thu, 4 Apr 2019 14:07:57 -0700 From: "Paul E. McKenney" To: Neeraj Upadhyay Cc: Mukesh Ojha , josh@joshtriplett.org, rostedt@goodmis.org, mathieu.desnoyers@efficios.com, jiangshanlai@gmail.com, joel@joelfernandes.org, rcu@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] rcu: tree_stall: Correctly unlock root node in rcu_check_gp_start_stall Reply-To: paulmck@linux.ibm.com References: <1553858828-23097-1-git-send-email-neeraju@codeaurora.org> <7a9eed5a-9bcf-460c-abb9-1e9bd6eae102@codeaurora.org> <2a8057f7-0704-5e8f-423e-e56a91a9b448@codeaurora.org> <20190329212755.GB4102@linux.ibm.com> <10b7ba19-9184-a4aa-d609-a644fcbe0503@codeaurora.org> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <10b7ba19-9184-a4aa-d609-a644fcbe0503@codeaurora.org> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-GCONF: 00 x-cbid: 19040421-0072-0000-0000-00000415A8C6 X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00010873; HX=3.00000242; KW=3.00000007; PH=3.00000004; SC=3.00000284; SDB=6.01184369; UDB=6.00620132; IPR=6.00965122; MB=3.00026298; MTD=3.00000008; XFM=3.00000015; UTC=2019-04-04 21:08:00 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 19040421-0073-0000-0000-00004BB67CDA Message-Id: <20190404210757.GO14111@linux.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2019-04-04_12:,, 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=8.0.1-1810050000 definitions=main-1904040134 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Mar 30, 2019 at 09:14:36AM +0530, Neeraj Upadhyay wrote: > On 3/30/19 2:57 AM, Paul E. McKenney wrote: > >On Fri, Mar 29, 2019 at 07:52:15PM +0530, Neeraj Upadhyay wrote: > >> > >> > >>On 3/29/19 6:58 PM, Mukesh Ojha wrote: > >>> > >>>On 3/29/2019 4:57 PM, Neeraj Upadhyay wrote: > >>>>Only unlock the root node, if current node (rnp) is not > >>>>root node. > >>>> > >>>>Signed-off-by: Neeraj Upadhyay > >>> > >>> > >>> > >>>>--- > >>>>   kernel/rcu/tree_stall.h | 4 +++- > >>>>   1 file changed, 3 insertions(+), 1 deletion(-) > >>>> > >>>>diff --git a/kernel/rcu/tree_stall.h b/kernel/rcu/tree_stall.h > >>>>index f65a73a..0651833 100644 > >>>>--- a/kernel/rcu/tree_stall.h > >>>>+++ b/kernel/rcu/tree_stall.h > >>> > >>> > >>>why this is showing as under tree_stall.h while it is under > >>>"kernel/rcu/tree.c" > >> > >>It's moved in https://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git/commit/?h=dev&id=10462d6f58fb6dbde7563e9343505d98d5bfba3d > >> > >>Please see linux-rcu dev tree for other changes, which moves code to > >>this file. > >> > >> > >>Thanks > >>Neeraj > >> > >>> > >>>>@@ -630,7 +630,9 @@ static void rcu_check_gp_start_stall(struct > >>>>rcu_node *rnp, struct rcu_data *rdp, > >>>>           time_before(j, rcu_state.gp_req_activity + gpssdelay) || > >>>>           time_before(j, rcu_state.gp_activity + gpssdelay) || > >>>>           atomic_xchg(&warned, 1)) { > >>>>-        raw_spin_unlock_rcu_node(rnp_root); /* irqs remain disabled. */ > >>>>+        if (rnp_root != rnp) > >>>>+            /* irqs remain disabled. */ > >>>>+            raw_spin_unlock_rcu_node(rnp_root); > >>> > >>>Looks good as it will balance the lock .if it is the root_node, > >>>which was not there earlier, and unlock was happening without any > >>>lock on root. > >>> > >>>Reviewed-by: Mukesh Ojha > > > >Applied, again thank you both! > > > >In both cases, I updated the commit log, so please check to make sure > >that I didn't mess anything up. > > > > Thanx, Paul > > > > Thanks Paul. One minor comment on https://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git/commit/?h=dev&id=ec6530e763046b6bb1f4c2c2aed49ebc68aae2a0 > > > "it clearly does not make sense to release > both rnp->lock and rnp->lock" > > should be rnp->lock and rnp_root->lock Good eyes, fixed, thank you! Thanx, Paul > Thanks > Neeraj > > >>>Cheers, > >>>-Mukesh > >>> > >>>>           raw_spin_unlock_irqrestore_rcu_node(rnp, flags); > >>>>           return; > >>>>       } > >> > >>-- > >>QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a > >>member of the Code Aurora Forum, hosted by The Linux Foundation > >> > > > > -- > QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a > member of the Code Aurora Forum, hosted by The Linux Foundation >