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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Mon, 25 Jun 2018 19:02:24 -0400 Received: from b01ledav003.gho.pok.ibm.com (b01ledav003.gho.pok.ibm.com [9.57.199.108]) by b01cxnp23032.gho.pok.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id w5PN2ONZ19071256 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL); Mon, 25 Jun 2018 23:02:24 GMT Received: from b01ledav003.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id B9F36B2072; Mon, 25 Jun 2018 19:02:18 -0400 (EDT) Received: from b01ledav003.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id A456BB2068; Mon, 25 Jun 2018 19:02:18 -0400 (EDT) Received: from paulmck-ThinkPad-W541 (unknown [9.70.82.159]) by b01ledav003.gho.pok.ibm.com (Postfix) with ESMTP; Mon, 25 Jun 2018 19:02:18 -0400 (EDT) Received: by paulmck-ThinkPad-W541 (Postfix, from userid 1000) id 02E9816C9ED2; Mon, 25 Jun 2018 16:04:28 -0700 (PDT) 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, fweisbec@gmail.com, oleg@redhat.com, joel@joelfernandes.org, "Paul E. McKenney" Subject: [PATCH tip/core/rcu 5/5] rcu: Make rcu_gp_cleanup() write only once to ->gp_flags Date: Mon, 25 Jun 2018 16:04:27 -0700 X-Mailer: git-send-email 2.17.1 In-Reply-To: <20180625230410.GA13250@linux.vnet.ibm.com> References: <20180625230410.GA13250@linux.vnet.ibm.com> X-TM-AS-GCONF: 00 x-cbid: 18062523-0064-0000-0000-0000032029B7 X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00009255; HX=3.00000241; KW=3.00000007; PH=3.00000004; SC=3.00000266; SDB=6.01052306; UDB=6.00539451; IPR=6.00830232; MB=3.00021855; MTD=3.00000008; XFM=3.00000015; UTC=2018-06-25 23:02:28 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 18062523-0065-0000-0000-000039B7224B Message-Id: <20180625230427.13877-5-paulmck@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2018-06-25_11:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=1 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=860 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1806210000 definitions=main-1806250260 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org At the end of rcu_gp_cleanup(), if another grace period is needed, but not via rcu_accelerate_cbs(), the ->gp_flags field is written twice, once when making the new grace-period request, and once when clearing all other types of requests. This commit therefore adds an else-clause to avoid this double write. Signed-off-by: Paul E. McKenney --- kernel/rcu/tree.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index fae4df831e52..2db3475c2924 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -2117,8 +2117,9 @@ static void rcu_gp_cleanup(struct rcu_state *rsp) rsp->gp_req_activity = jiffies; trace_rcu_grace_period(rsp->name, READ_ONCE(rsp->gpnum), TPS("newreq")); + } else { + WRITE_ONCE(rsp->gp_flags, rsp->gp_flags & RCU_GP_FLAG_INIT); } - WRITE_ONCE(rsp->gp_flags, rsp->gp_flags & RCU_GP_FLAG_INIT); raw_spin_unlock_irq_rcu_node(rnp); } -- 2.17.1