From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751022AbdAXVqm (ORCPT ); Tue, 24 Jan 2017 16:46:42 -0500 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:44198 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750807AbdAXVqk (ORCPT ); Tue, 24 Jan 2017 16:46:40 -0500 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, dvhart@linux.intel.com, fweisbec@gmail.com, oleg@redhat.com, bobby.prani@gmail.com, "Paul E. McKenney" Subject: [PATCH v3 tip/core/rcu 2/6] rcu: Abstract the dynticks snapshot operation Date: Tue, 24 Jan 2017 13:46:29 -0800 X-Mailer: git-send-email 2.5.2 In-Reply-To: <20170124214602.GA2269@linux.vnet.ibm.com> References: <20170124214602.GA2269@linux.vnet.ibm.com> X-TM-AS-GCONF: 00 X-Content-Scanned: Fidelis XPS MAILER x-cbid: 17012421-0028-0000-0000-000006DE99F7 X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00006492; HX=3.00000240; KW=3.00000007; PH=3.00000004; SC=3.00000200; SDB=6.00812179; UDB=6.00396063; IPR=6.00589597; BA=6.00005085; NDR=6.00000001; ZLA=6.00000005; ZF=6.00000009; ZB=6.00000000; ZP=6.00000000; ZH=6.00000000; ZU=6.00000002; MB=3.00014031; XFM=3.00000011; UTC=2017-01-24 21:46:38 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 17012421-0029-0000-0000-000032FEF039 Message-Id: <1485294393-10785-2-git-send-email-paulmck@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2017-01-24_17:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 suspectscore=1 malwarescore=0 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1612050000 definitions=main-1701240129 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This commit is the second step towards full abstraction of all accesses to the ->dynticks counter, implementing the previously open-coded atomic add of zero in a new rcu_dynticks_snap() function. This abstraction will ease changes o the ->dynticks counter operation. Signed-off-by: Paul E. McKenney Reviewed-by: Josh Triplett --- kernel/rcu/tree.c | 19 ++++++++++++++++--- kernel/rcu/tree_exp.h | 6 ++---- 2 files changed, 18 insertions(+), 7 deletions(-) diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 14e283c351f6..805d55ee0b2a 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -282,6 +282,17 @@ static DEFINE_PER_CPU(struct rcu_dynticks, rcu_dynticks) = { }; /* + * Snapshot the ->dynticks counter with full ordering so as to allow + * stable comparison of this counter with past and future snapshots. + */ +static int rcu_dynticks_snap(struct rcu_dynticks *rdtp) +{ + int snap = atomic_add_return(0, &rdtp->dynticks); + + return snap; +} + +/* * Do a double-increment of the ->dynticks counter to emulate a * momentary idle-CPU quiescent state. */ @@ -1049,7 +1060,9 @@ void rcu_nmi_exit(void) */ bool notrace __rcu_is_watching(void) { - return atomic_read(this_cpu_ptr(&rcu_dynticks.dynticks)) & 0x1; + struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks); + + return atomic_read(&rdtp->dynticks) & 0x1; } /** @@ -1132,7 +1145,7 @@ static int rcu_is_cpu_rrupt_from_idle(void) static int dyntick_save_progress_counter(struct rcu_data *rdp, bool *isidle, unsigned long *maxj) { - rdp->dynticks_snap = atomic_add_return(0, &rdp->dynticks->dynticks); + rdp->dynticks_snap = rcu_dynticks_snap(rdp->dynticks); rcu_sysidle_check_cpu(rdp, isidle, maxj); if ((rdp->dynticks_snap & 0x1) == 0) { trace_rcu_fqs(rdp->rsp->name, rdp->gpnum, rdp->cpu, TPS("dti")); @@ -1157,7 +1170,7 @@ static int rcu_implicit_dynticks_qs(struct rcu_data *rdp, int *rcrmp; unsigned int snap; - curr = (unsigned int)atomic_add_return(0, &rdp->dynticks->dynticks); + curr = (unsigned int)rcu_dynticks_snap(rdp->dynticks); snap = (unsigned int)rdp->dynticks_snap; /* diff --git a/kernel/rcu/tree_exp.h b/kernel/rcu/tree_exp.h index e59e1849b89a..011f626b2fd8 100644 --- a/kernel/rcu/tree_exp.h +++ b/kernel/rcu/tree_exp.h @@ -356,10 +356,9 @@ static void sync_rcu_exp_select_cpus(struct rcu_state *rsp, mask_ofl_test = 0; for_each_leaf_node_possible_cpu(rnp, cpu) { struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu); - struct rcu_dynticks *rdtp = &per_cpu(rcu_dynticks, cpu); rdp->exp_dynticks_snap = - atomic_add_return(0, &rdtp->dynticks); + rcu_dynticks_snap(rdp->dynticks); if (raw_smp_processor_id() == cpu || !(rdp->exp_dynticks_snap & 0x1) || !(rnp->qsmaskinitnext & rdp->grpmask)) @@ -380,12 +379,11 @@ static void sync_rcu_exp_select_cpus(struct rcu_state *rsp, for_each_leaf_node_possible_cpu(rnp, cpu) { unsigned long mask = leaf_node_cpu_bit(rnp, cpu); struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu); - struct rcu_dynticks *rdtp = &per_cpu(rcu_dynticks, cpu); if (!(mask_ofl_ipi & mask)) continue; retry_ipi: - if (atomic_add_return(0, &rdtp->dynticks) != + if (rcu_dynticks_snap(rdp->dynticks) != rdp->exp_dynticks_snap) { mask_ofl_test |= mask; continue; -- 2.5.2