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McKenney" , Ingo Molnar , Peter Zijlstra , Sasha Levin Subject: [PATCH AUTOSEL for 4.4 089/115] sched: Stop resched_cpu() from sending IPIs to offline CPUs Thread-Topic: [PATCH AUTOSEL for 4.4 089/115] sched: Stop resched_cpu() from sending IPIs to offline CPUs Thread-Index: AQHTsz9nT3uXC/R6/U2MY7ELD5NOgA== Date: Sat, 3 Mar 2018 22:31:42 +0000 Message-ID: <20180303223010.27106-89-alexander.levin@microsoft.com> References: <20180303223010.27106-1-alexander.levin@microsoft.com> In-Reply-To: <20180303223010.27106-1-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;MW2PR2101MB0939;7:IyPjz0CsKGBufvzQEMGI80TgSY6yQncLorrGI+Q4FEEyOhDGUqpA8dUZlO34QEa/yoBm2/qSCT9VFJksmRIfRGC21YyLNRHJEW6Q01icFhvXhdZ8ZmAHnWk+UUXz5NydUDxc4gb2AWwi2Hr4ib0UO8qgz2lqTTOCmu0hB/oqB2KNZPEfqN+Xr1zvUDGiFAklorR747sMYZXrMJQgsFqriQWx777hUgNnZrTQBdcU8Gy8XK84m++YyZUHkaoJ/Rto x-ms-office365-filtering-ht: Tenant x-ms-office365-filtering-correlation-id: 280d9fb5-374b-46b5-25af-08d58157b995 x-microsoft-antispam: UriScan:;BCL:0;PCL:0;RULEID:(7020095)(4652020)(48565401081)(5600026)(4604075)(3008032)(4534165)(4627221)(201703031133081)(201702281549075)(2017052603307)(7193020);SRVR:MW2PR2101MB0939; x-ms-traffictypediagnostic: MW2PR2101MB0939: 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)(3231220)(944501244)(52105095)(3002001)(10201501046)(93006095)(93001095)(6055026)(61426038)(61427038)(6041288)(201703131423095)(201702281528075)(20161123555045)(201703061421075)(201703061406153)(20161123560045)(20161123564045)(20161123558120)(20161123562045)(6072148)(201708071742011);SRVR:MW2PR2101MB0939;BCL:0;PCL:0;RULEID:;SRVR:MW2PR2101MB0939; x-forefront-prvs: 0600F93FE1 x-forefront-antispam-report: SFV:NSPM;SFS:(10019020)(396003)(346002)(366004)(376002)(39380400002)(39860400002)(189003)(199004)(86612001)(76176011)(478600001)(81166006)(81156014)(72206003)(5660300001)(8936002)(25786009)(59450400001)(26005)(6506007)(102836004)(316002)(22452003)(6486002)(8676002)(14454004)(4326008)(6436002)(107886003)(10090500001)(6512007)(53936002)(36756003)(10290500003)(86362001)(575784001)(2900100001)(3660700001)(305945005)(2950100002)(5250100002)(99286004)(3280700002)(97736004)(54906003)(110136005)(6666003)(2501003)(186003)(106356001)(7736002)(66066001)(3846002)(2906002)(6116002)(105586002)(68736007)(1076002)(22906009)(217873001);DIR:OUT;SFP:1102;SCL:1;SRVR:MW2PR2101MB0939;H:MW2PR2101MB1034.namprd21.prod.outlook.com;FPR:;SPF:None;PTR:InfoNoRecords;MX:1;A:1;LANG:en; x-microsoft-antispam-message-info: YaTAnE/WZbibfzZUhcpyDxquwkJYfVHzOfyTQjIvAtX3x9BJlBwtMdK4Yiyp0NZ2eKO20iGZlfzj90xSFyMiJv2lZjniucVnkmvM63ogl3OZ2gqxhM8Cjfg6yL5ukcznrRfNwKdPws8gB6m7CPq+BDzU0Adt01aJA5XuEKFyTN0= 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: 280d9fb5-374b-46b5-25af-08d58157b995 X-MS-Exchange-CrossTenant-originalarrivaltime: 03 Mar 2018 22:31:42.9333 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 72f988bf-86f1-41af-91ab-2d7cd011db47 X-MS-Exchange-Transport-CrossTenantHeadersStamped: MW2PR2101MB0939 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 c5b1c62623cf..65ed3501c2ca 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -601,7 +601,8 @@ 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