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McKenney" , Ingo Molnar , Peter Zijlstra , Sasha Levin Subject: [PATCH AUTOSEL for 4.15 020/102] sched: Stop resched_cpu() from sending IPIs to offline CPUs Thread-Topic: [PATCH AUTOSEL for 4.15 020/102] sched: Stop resched_cpu() from sending IPIs to offline CPUs Thread-Index: AQHTsz5g9Ba0E/dL2kW7vLDiGpJ7FA== Date: Sat, 3 Mar 2018 22:24:21 +0000 Message-ID: <20180303222318.26006-20-alexander.levin@microsoft.com> References: <20180303222318.26006-1-alexander.levin@microsoft.com> In-Reply-To: <20180303222318.26006-1-alexander.levin@microsoft.com> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [52.168.54.252] x-ms-publictraffictype: Email x-microsoft-exchange-diagnostics: 1;MW2PR2101MB0890;7:bj9KMLaSBHAoOkymS4D4LMVuKSx8vIFA+2HIqOimkdktC3UKiLM46hZfo8fd4ikW7eFDd5qc+A6yAq8c4/7YuEZKq5BJabsrUNcS2vHa64w0ByUhB9/8La+OnJzb0zQkXdXT9RrYYja+2RcbepGYHREa1IFzDJghWqfb8qth7LVkNP1P7Ds0w+to+/V0TiXPZ6ivHz9VFdqbDo5KNhLcKgi4XBw1JFTsZnRNGBSSG9aXTxAaQaD9QAfDEpBqOYM7 x-ms-office365-filtering-ht: Tenant x-ms-office365-filtering-correlation-id: 7cba8ea7-703f-4b31-9a27-08d58155914f x-microsoft-antispam: UriScan:;BCL:0;PCL:0;RULEID:(7020095)(4652020)(4534165)(4627221)(201703031133081)(201702281549075)(48565401081)(5600026)(4604075)(3008032)(2017052603307)(7193020);SRVR:MW2PR2101MB0890; x-ms-traffictypediagnostic: MW2PR2101MB0890: authentication-results: spf=none (sender IP is ) smtp.mailfrom=Alexander.Levin@microsoft.com; x-microsoft-antispam-prvs: x-exchange-antispam-report-test: UriScan:(28532068793085)(89211679590171)(209352067349851)(104084551191319); x-exchange-antispam-report-cfa-test: BCL:0;PCL:0;RULEID:(8211001083)(61425038)(6040501)(2401047)(8121501046)(5005006)(3002001)(10201501046)(3231220)(944501244)(52105095)(93006095)(93001095)(6055026)(61426038)(61427038)(6041288)(201703131423095)(201702281528075)(20161123555045)(201703061421075)(201703061406153)(20161123558120)(20161123560045)(20161123564045)(20161123562045)(6072148)(201708071742011);SRVR:MW2PR2101MB0890;BCL:0;PCL:0;RULEID:;SRVR:MW2PR2101MB0890; x-forefront-prvs: 0600F93FE1 x-forefront-antispam-report: SFV:NSPM;SFS:(10019020)(39380400002)(366004)(346002)(376002)(396003)(39860400002)(199004)(189003)(575784001)(86362001)(105586002)(1076002)(14454004)(8936002)(6436002)(66066001)(59450400001)(6506007)(2906002)(99286004)(53936002)(6512007)(25786009)(97736004)(76176011)(6116002)(6486002)(3846002)(4326008)(86612001)(186003)(3280700002)(2501003)(316002)(22452003)(72206003)(5660300001)(2950100002)(8676002)(81156014)(102836004)(81166006)(6666003)(68736007)(107886003)(305945005)(478600001)(54906003)(10090500001)(7736002)(10290500003)(106356001)(110136005)(36756003)(2900100001)(3660700001)(5250100002)(26005)(22906009)(217873001);DIR:OUT;SFP:1102;SCL:1;SRVR:MW2PR2101MB0890;H:MW2PR2101MB1034.namprd21.prod.outlook.com;FPR:;SPF:None;PTR:InfoNoRecords;A:1;MX:1;LANG:en; x-microsoft-antispam-message-info: YHuXogDlScBqzePTNbz+BqI0N3jls049iGCQJPN3TTWktCySG97S1E5enGNS/ukDVqs6h24Yg7UNrsxMn1dSiuaZCPZdlKhSc/mBdFfxezDTfUG/Yzt3jCQO+wXRdIwoQbziPk1MzNnKgS6h0WvWByRxLxGz4E4xrLWYAOXB9V4= spamdiagnosticoutput: 1:99 spamdiagnosticmetadata: NSPM Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-OriginatorOrg: microsoft.com X-MS-Exchange-CrossTenant-Network-Message-Id: 7cba8ea7-703f-4b31-9a27-08d58155914f X-MS-Exchange-CrossTenant-originalarrivaltime: 03 Mar 2018 22:24:21.1034 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 72f988bf-86f1-41af-91ab-2d7cd011db47 X-MS-Exchange-Transport-CrossTenantHeadersStamped: MW2PR2101MB0890 Sender: stable-owner@vger.kernel.org X-Mailing-List: stable@vger.kernel.org X-getmail-retrieved-from-mailbox: INBOX X-Mailing-List: linux-kernel@vger.kernel.org List-ID: From: "Paul E. McKenney" [ Upstream commit a0982dfa03efca6c239c52cabebcea4afb93ea6b ] The rcutorture test suite occasionally provokes a splat due to invoking resched_cpu() on an offline CPU: WARNING: CPU: 2 PID: 8 at /home/paulmck/public_git/linux-rcu/arch/x86/kerne= l/smp.c:128 native_smp_send_reschedule+0x37/0x40 Modules linked in: CPU: 2 PID: 8 Comm: rcu_preempt Not tainted 4.14.0-rc4+ #1 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Ubuntu-1.8.2-1u= buntu1 04/01/2014 task: ffff902ede9daf00 task.stack: ffff96c50010c000 RIP: 0010:native_smp_send_reschedule+0x37/0x40 RSP: 0018:ffff96c50010fdb8 EFLAGS: 00010096 RAX: 000000000000002e RBX: ffff902edaab4680 RCX: 0000000000000003 RDX: 0000000080000003 RSI: 0000000000000000 RDI: 00000000ffffffff RBP: ffff96c50010fdb8 R08: 0000000000000000 R09: 0000000000000001 R10: 0000000000000000 R11: 00000000299f36ae R12: 0000000000000001 R13: ffffffff9de64240 R14: 0000000000000001 R15: ffffffff9de64240 FS: 0000000000000000(0000) GS:ffff902edfc80000(0000) knlGS:000000000000000= 0 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00000000f7d4c642 CR3: 000000001e0e2000 CR4: 00000000000006e0 Call Trace: resched_curr+0x8f/0x1c0 resched_cpu+0x2c/0x40 rcu_implicit_dynticks_qs+0x152/0x220 force_qs_rnp+0x147/0x1d0 ? sync_rcu_exp_select_cpus+0x450/0x450 rcu_gp_kthread+0x5a9/0x950 kthread+0x142/0x180 ? force_qs_rnp+0x1d0/0x1d0 ? kthread_create_on_node+0x40/0x40 ret_from_fork+0x27/0x40 Code: 14 01 0f 92 c0 84 c0 74 14 48 8b 05 14 4f f4 00 be fd 00 00 00 ff 90 = a0 00 00 00 5d c3 89 fe 48 c7 c7 38 89 ca 9d e8 e5 56 08 00 <0f> ff 5d c3 0= f 1f 44 00 00 8b 05 52 9e 37 02 85 c0 75 38 55 48 ---[ end trace 26df9e5df4bba4ac ]--- This splat cannot be generated by expedited grace periods because they always invoke resched_cpu() on the current CPU, which is good because expedited grace periods require that resched_cpu() unconditionally succeed. However, other parts of RCU can tolerate resched_cpu() acting as a no-op, at least as long as it doesn't happen too often. This commit therefore makes resched_cpu() invoke resched_curr() only if the CPU is either online or is the current CPU. Signed-off-by: Paul E. McKenney Cc: Ingo Molnar Cc: Peter Zijlstra Signed-off-by: Sasha Levin --- kernel/sched/core.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index a7bf32aabfda..5a31a85bbd84 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -508,7 +508,8 @@ void resched_cpu(int cpu) unsigned long flags; =20 raw_spin_lock_irqsave(&rq->lock, flags); - resched_curr(rq); + if (cpu_online(cpu) || cpu =3D=3D smp_processor_id()) + resched_curr(rq); raw_spin_unlock_irqrestore(&rq->lock, flags); } =20 --=20 2.14.1