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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Fri, 2 Aug 2019 16:15:02 +0100 Received: from b01ledav003.gho.pok.ibm.com (b01ledav003.gho.pok.ibm.com [9.57.199.108]) by b01cxnp23033.gho.pok.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id x72FF1Bl35783164 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Fri, 2 Aug 2019 15:15:01 GMT Received: from b01ledav003.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 09DA4B2067; Fri, 2 Aug 2019 15:15:01 +0000 (GMT) Received: from b01ledav003.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id E5252B206E; Fri, 2 Aug 2019 15:15:00 +0000 (GMT) Received: from paulmck-ThinkPad-W541 (unknown [9.70.82.154]) by b01ledav003.gho.pok.ibm.com (Postfix) with ESMTP; Fri, 2 Aug 2019 15:15:00 +0000 (GMT) Received: by paulmck-ThinkPad-W541 (Postfix, from userid 1000) id 2E6E316C9A56; Fri, 2 Aug 2019 08:15:02 -0700 (PDT) From: "Paul E. McKenney" To: rcu@vger.kernel.org Cc: linux-kernel@vger.kernel.org, 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 RFC tip/core/rcu 14/14] rcu/nohz: Make multi_cpu_stop() enable tick on all online CPUs Date: Fri, 2 Aug 2019 08:15:01 -0700 X-Mailer: git-send-email 2.17.1 In-Reply-To: <20190802151435.GA1081@linux.ibm.com> References: <20190802151435.GA1081@linux.ibm.com> X-TM-AS-GCONF: 00 x-cbid: 19080215-0072-0000-0000-0000045004AA X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00011538; HX=3.00000242; KW=3.00000007; PH=3.00000004; SC=3.00000287; SDB=6.01241059; UDB=6.00654493; IPR=6.01022491; MB=3.00028010; MTD=3.00000008; XFM=3.00000015; UTC=2019-08-02 15:15:06 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 19080215-0073-0000-0000-00004CC104B1 Message-Id: <20190802151501.13069-14-paulmck@linux.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2019-08-02_07:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=13 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=553 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1906280000 definitions=main-1908020156 Sender: rcu-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: rcu@vger.kernel.org The multi_cpu_stop() function relies on the scheduler to gain control from whatever is running on the various online CPUs, including any nohz_full CPUs running long loops in kernel-mode code. Lack of the scheduler-clock interrupt on such CPUs can delay multi_cpu_stop() for several minutes and can also result in RCU CPU stall warnings. This commit therefore causes multi_cpu_stop() to enable the scheduler-clock interrupt on all online CPUs. Signed-off-by: Paul E. McKenney --- kernel/stop_machine.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/kernel/stop_machine.c b/kernel/stop_machine.c index b4f83f7bdf86..a2659f61ed92 100644 --- a/kernel/stop_machine.c +++ b/kernel/stop_machine.c @@ -20,6 +20,7 @@ #include #include #include +#include #include /* @@ -187,15 +188,19 @@ static int multi_cpu_stop(void *data) { struct multi_stop_data *msdata = data; enum multi_stop_state curstate = MULTI_STOP_NONE; - int cpu = smp_processor_id(), err = 0; + int cpu, err = 0; const struct cpumask *cpumask; unsigned long flags; bool is_active; + for_each_online_cpu(cpu) + tick_nohz_dep_set_cpu(cpu, TICK_DEP_MASK_RCU); + /* * When called from stop_machine_from_inactive_cpu(), irq might * already be disabled. Save the state and restore it on exit. */ + cpu = smp_processor_id(); local_save_flags(flags); if (!msdata->active_cpus) { @@ -236,6 +241,8 @@ static int multi_cpu_stop(void *data) } while (curstate != MULTI_STOP_EXIT); local_irq_restore(flags); + for_each_online_cpu(cpu) + tick_nohz_dep_clear_cpu(cpu, TICK_DEP_MASK_RCU); return err; } -- 2.17.1