Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753901AbaLDKoI (ORCPT ); Thu, 4 Dec 2014 05:44:08 -0500 Received: from mail-oi0-f47.google.com ([209.85.218.47]:35615 "EHLO mail-oi0-f47.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753424AbaLDKoG (ORCPT ); Thu, 4 Dec 2014 05:44:06 -0500 MIME-Version: 1.0 In-Reply-To: <27240C0AC20F114CBF8149A2696CBE4A01EEA337@SHSMSX101.ccr.corp.intel.com> References: <007f01d00fa1$68bf6770$3a3e3650$@alibaba-inc.com> <27240C0AC20F114CBF8149A2696CBE4A01EEA337@SHSMSX101.ccr.corp.intel.com> From: Vincent Guittot Date: Thu, 4 Dec 2014 11:43:45 +0100 Message-ID: Subject: Re: [PATCH] sched/fair: fix select_task_rq_fair return -1 To: "Liu, Chuansheng" Cc: Hillf Danton , "Zhang, Jun" , Ingo Molnar , Peter Zijlstra , linux-kernel , "Liu, Changcheng" Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 4 December 2014 at 11:23, Liu, Chuansheng wrote: > > >> -----Original Message----- >> From: Vincent Guittot [mailto:vincent.guittot@linaro.org] >> Sent: Thursday, December 04, 2014 6:08 PM >> To: Hillf Danton >> Cc: Zhang, Jun; Ingo Molnar; Peter Zijlstra; linux-kernel; Liu, Chuansheng; Liu, >> Changcheng >> Subject: Re: [PATCH] sched/fair: fix select_task_rq_fair return -1 >> >> On 4 December 2014 at 10:05, Hillf Danton wrote: >> >> >> >> From: zhang jun >> >> >> >> when cpu == -1 and sd->child == NULL, select_task_rq_fair return -1, system >> panic. >> >> >> >> [ 0.738326] BUG: unable to handle kernel paging request at >> ffff8800997ea928 >> >> [ 0.746138] IP: [] wake_up_new_task+0x43/0x1b0 >> >> [ 0.752886] PGD 25df067 PUD 0 >> >> [ 0.756321] Oops: 0000 1 PREEMPT SMP >> >> [ 0.760743] Modules linked in: >> >> [ 0.764179] CPU: 0 PID: 6 Comm: kworker/u8:0 Not tainted >> 3.14.19-quilt-b27ac761 #2 >> >> [ 0.772651] Hardware name: Intel Corporation CHERRYVIEW B1 >> PLATFORM/Cherry Trail CR, BIOS CHTTRVP1.X64.0003.R08.1411110453 >> >> 11/11/2014 >> >> [ 0.786084] Workqueue: khelper __call_usermodehelper >> >> [ 0.791649] task: ffff88007955a150 ti: ffff88007955c000 task.ti: >> ffff88007955c000 >> >> [ 0.800021] RIP: 0010:[] [] >> wake_up_new_task+0x43/0x1b0 >> >> [ 0.809478] RSP: 0000:ffff88007955dd58 EFLAGS: 00010092 >> >> [ 0.815422] RAX: 00000000ffffffff RBX: 0000000000000001 RCX: >> 0000000000000020 >> >> [ 0.823404] RDX: 00000000ffffffff RSI: 0000000000000020 RDI: >> 0000000000000020 >> >> [ 0.831386] RBP: ffff88007955dd80 R08: ffff880079604b58 R09: >> 00000000ffffffff >> >> [ 0.839368] R10: 0000000000000004 R11: eae0000000000000 R12: >> ffff8800797ea650 >> >> [ 0.847350] R13: 0000000000004000 R14: ffff8800797ead52 R15: >> 0000000000000206 >> >> [ 0.855335] FS: 0000000000000000(0000) GS:ffff88007aa00000(0000) >> knlGS:0000000000000000 >> >> [ 0.864387] CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b >> >> [ 0.870817] CR2: ffff8800997ea928 CR3: 000000000220b000 CR4: >> 00000000001007f0 >> >> [ 0.878796] Stack: >> >> [ 0.881046] 0000000000000001 ffff8800797ea650 0000000000004000 >> 0000000000000000 >> >> [ 0.889363] 000000000000003c ffff88007955ddf0 ffffffff8107ddfd >> ffffffff810b6a95 >> >> [ 0.897680] 0000000000000000 ffff8800796beb00 ffff880000000000 >> ffffffff81000000 >> >> [ 0.905998] Call Trace: >> >> [ 0.908752] [] do_fork+0x12d/0x3b0 >> >> [ 0.914416] [] ? set_next_entity+0x95/0xb0 >> >> [ 0.920856] [] kernel_thread+0x26/0x30 >> >> [ 0.926903] [] __call_usermodehelper+0x2e/0x90 >> >> [ 0.933730] [] process_one_work+0x171/0x490 >> >> [ 0.940264] [] worker_thread+0x11b/0x3a0 >> >> [ 0.946508] [] ? manage_workers.isra.27+0x2b0/0x2b0 >> >> [ 0.953821] [] kthread+0xd2/0xf0 >> >> [ 0.959289] [] ? kthread_create_on_node+0x170/0x170 >> >> [ 0.966602] [] ret_from_fork+0x7c/0xb0 >> >> [ 0.972652] [] ? kthread_create_on_node+0x170/0x170 >> >> [ 0.979956] Code: 49 89 fc 4c 89 f7 53 e8 bc 5c a4 00 49 8b 54 24 08 31 c9 49 >> 89 c7 49 8b 44 24 60 4c 89 e7 8b 72 18 ba 08 00 00 00 ff 50 40 89 >> >> c2 <49> 0f a3 94 24 e0 02 00 00 19 c9 85 c9 0f 84 34 01 00 00 48 8b >> >> [ 1.001809] RIP [] wake_up_new_task+0x43/0x1b0 >> >> [ 1.008641] RSP >> >> [ 1.012544] CR2: ffff8800997ea928 >> >> [ 1.016279] --[ end trace 9737aaa337a5ca10 ]-- >> >> >> >> Signed-off-by: zhang jun >> >> Signed-off-by: Chuansheng Liu >> >> Signed-off-by: Changcheng Liu >> >> --- >> >> kernel/sched/fair.c | 2 ++ >> >> 1 file changed, 2 insertions(+) >> >> >> >> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c >> >> index 34baa60..123153f 100644 >> >> --- a/kernel/sched/fair.c >> >> +++ b/kernel/sched/fair.c >> >> @@ -4587,6 +4587,8 @@ select_task_rq_fair(struct task_struct *p, int >> prev_cpu, int sd_flag, int wake_f >> >> if (new_cpu == -1 || new_cpu == cpu) { >> >> /* Now try balancing at a lower domain level of >> cpu */ >> >> sd = sd->child; >> >> + if ((!sd) && (new_cpu == -1)) >> >> + new_cpu = smp_processor_id(); >> >> continue; >> >> } >> >> >> > In 3.18-rc7 is -1 still selected? >> >> find_idlest_cpu doesn't return -1 anymore but always a valid cpu. The >> local cpu will be used if no better cpu has been found > > So I guess we can make one similar patch based on 3.14.x branch? > Latest: > find_idlest_cpu(struct sched_group *group, struct task_struct *p, int this_cpu) > return shallowest_idle_cpu != -1 ? shallowest_idle_cpu : least_loaded_cpu; > > 3.14.X: > find_idlest_cpu(struct sched_group *group, struct task_struct *p, int this_cpu) > return idlest; The change below will give a similar behavior than 3.18 for 3.14 and we still match the condition if (new_cpu == -1 || new_cpu == cpu) in order to go in the child level --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -4151,7 +4151,7 @@ static int find_idlest_cpu(struct sched_group *group, struct task_struct *p, int this_cpu) { unsigned long load, min_load = ULONG_MAX; - int idlest = -1; + int idlest = this_cpu; int i; /* Traverse only the allowed CPUs */ > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/