From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751577AbdARGFM (ORCPT ); Wed, 18 Jan 2017 01:05:12 -0500 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:58503 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1750830AbdARGFK (ORCPT ); Wed, 18 Jan 2017 01:05:10 -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 v2 tip/core/rcu 07/18] rcu: Add long-term CPU kicking Date: Tue, 17 Jan 2017 18:53:46 -0800 X-Mailer: git-send-email 2.5.2 In-Reply-To: <20170118025316.GB2042@linux.vnet.ibm.com> References: <20170118025316.GB2042@linux.vnet.ibm.com> X-TM-AS-GCONF: 00 X-Content-Scanned: Fidelis XPS MAILER x-cbid: 17011802-0020-0000-0000-00000B19FD6D X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00006453; HX=3.00000240; KW=3.00000007; PH=3.00000004; SC=3.00000199; SDB=6.00809120; UDB=6.00394133; IPR=6.00586477; BA=6.00005066; NDR=6.00000001; ZLA=6.00000005; ZF=6.00000009; ZB=6.00000000; ZP=6.00000000; ZH=6.00000000; ZU=6.00000002; MB=3.00013954; XFM=3.00000011; UTC=2017-01-18 02:54:04 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 17011802-0021-0000-0000-0000594B8381 Message-Id: <1484708037-2523-7-git-send-email-paulmck@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2017-01-17_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-1701180043 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit d2db185bfee8 ("rcu: Remove short-term CPU kicking") removed frequent calls to resched_cpu(), which means that the only time resched_cpu() is invoked is after an RCU CPU stall warning. Although this is good from an avoid-IPIs perspective, we should try to break things loose -before- splatting. This commit therefore starts invoking resched_cpu() for each holdout at each force-quiescent-state interval that is more than halfway through the stall-warning interval. Signed-off-by: Paul E. McKenney --- kernel/rcu/tree.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 83bf054e194e..0e61b62e3f4a 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -1225,6 +1225,12 @@ static int rcu_implicit_dynticks_qs(struct rcu_data *rdp, rdp->rsp->gp_start + 2 * jiffies_till_sched_qs) || ULONG_CMP_GE(jiffies, rdp->rsp->gp_start + jiffies_till_sched_qs)) resched_cpu(rdp->cpu); /* Force CPU into scheduler. */ + /* + * If more than halfway to RCU CPU stall-warning time, do + * a resched_cpu() to try to loosen things up a bit. + */ + if (jiffies - rdp->rsp->gp_start > rcu_jiffies_till_stall_check() / 2) + resched_cpu(rdp->cpu); return 0; } -- 2.5.2