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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 15/22] rcu: Move grace-period pre-init delay after pre-init Date: Tue, 26 Jun 2018 10:10:41 -0700 X-Mailer: git-send-email 2.17.1 In-Reply-To: <20180626002052.GA24146@linux.vnet.ibm.com> References: <20180626002052.GA24146@linux.vnet.ibm.com> X-TM-AS-GCONF: 00 x-cbid: 18062617-0068-0000-0000-0000030E817E X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00009259; HX=3.00000241; KW=3.00000007; PH=3.00000004; SC=3.00000266; SDB=6.01052668; UDB=6.00539669; IPR=6.00830593; MB=3.00021864; MTD=3.00000008; XFM=3.00000015; UTC=2018-06-26 17:08:49 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 18062617-0069-0000-0000-000044D130D7 Message-Id: <20180626171048.2181-15-paulmck@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2018-06-26_08:,, 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=935 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1806210000 definitions=main-1806260192 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The main race with the early part of grace-period initialization appears to be with CPU hotplug. To more fully open this race window, this commit moves the rcu_gp_slow() from the beginning of the early initialization loop to follow that loop, thus widening the race window, especially for the rcu_node structures that are initialized last. This commit also expands rcutree.gp_preinit_delay from 3 to 12, giving the same overall delay in the grace period, but concentrated in the spot where it will do the most good. Signed-off-by: Paul E. McKenney --- kernel/rcu/tree.c | 2 +- tools/testing/selftests/rcutorture/configs/rcu/TREE03.boot | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-) diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index bb8f45c0fa68..7de1820a04c1 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -1900,7 +1900,6 @@ static bool rcu_gp_init(struct rcu_state *rsp) * will handle subsequent offline CPUs. */ rcu_for_each_leaf_node(rsp, rnp) { - rcu_gp_slow(rsp, gp_preinit_delay); spin_lock(&rsp->ofl_lock); raw_spin_lock_irq_rcu_node(rnp); if (rnp->qsmaskinit == rnp->qsmaskinitnext && @@ -1945,6 +1944,7 @@ static bool rcu_gp_init(struct rcu_state *rsp) raw_spin_unlock_irq_rcu_node(rnp); spin_unlock(&rsp->ofl_lock); } + rcu_gp_slow(rsp, gp_preinit_delay); /* Races with CPU hotplug. */ /* * Set the quiescent-state-needed bits in all the rcu_node diff --git a/tools/testing/selftests/rcutorture/configs/rcu/TREE03.boot b/tools/testing/selftests/rcutorture/configs/rcu/TREE03.boot index 5d2cc0bd50a0..b79ddb9eb9e8 100644 --- a/tools/testing/selftests/rcutorture/configs/rcu/TREE03.boot +++ b/tools/testing/selftests/rcutorture/configs/rcu/TREE03.boot @@ -1,5 +1,5 @@ rcutorture.onoff_interval=1 rcutorture.onoff_holdoff=30 -rcutree.gp_preinit_delay=3 +rcutree.gp_preinit_delay=12 rcutree.gp_init_delay=3 rcutree.gp_cleanup_delay=3 rcutree.kthread_prio=2 -- 2.17.1