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Message-Id: <2122191432730028@web8g.yandex.ru> Date: Wed, 27 May 2015 15:33:48 +0300 From: Kirill Tkhai <tkhai@...dex.ru> To: "bsegall@...gle.com" <bsegall@...gle.com> Cc: Mohammed Naser <mnaser@...xhost.com>, Peter Zijlstra <peterz@...radead.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "mingo@...hat.com" <mingo@...hat.com>, Konstantin Khlebnikov <khlebnikov@...dex-team.ru> Subject: Re: [PATCH] sched/fair: Fix null pointer dereference of empty queues Hi, Ben, 26.05.2015, 20:39, "bsegall@...gle.com" <bsegall@...gle.com>: > Kirill Tkhai <tkhai@...dex.ru> writes: >> Hi, >> >> 25.05.2015, 23:53, "Mohammed Naser" <mnaser@...xhost.com>: >>> Hi Peter, >>> >>> (resending as plain text, my bad) >>> >>> Thank you for reply. >>> >>> Would you have any ideas on why this would have occurred or other >>> steps to look at? It's my first time attempting to help fix a problem >>> like this. >>> >>> I have a crashdump of the kernel since this issue repeated itself a >>> few times on a loaded KVM host (it's 12GB however). I can also >>> provide the values of cfs_rq before the kernel crash. >>> >>> =================================== >>> [146055.357476] BUG: unable to handle kernel NULL pointer dereference >>> at 0000000000000038 >>> [146055.359620] IP: [<ffffffff810a7d31>] set_next_entity+0x11/0xb0 >>> [146055.361890] PGD 0 >>> [146055.364131] Oops: 0000 [#1] SMP >>> [146055.366475] Modules linked in: vhost_net vhost macvtap macvlan >>> act_police cls_u32 sch_ingress ipmi_si xt_multiport nf_conntrack_ipv6 >>> nf_defrag_ipv6 xt_mac xt_physdev xt_set iptable_raw ip_set_hash_ip >>> ip_set nfnetlink mpt3sas mpt2sas raid_class scsi_transport_sas mptctl >>> mptbase veth xt_CHECKSUM iptable_mangle ipt_MASQUERADE iptable_nat >>> nf_nat_ipv4 nf_nat nf_conntrack_ipv4 nf_defrag_ipv4 xt_conntrack >>> nf_conntrack ipt_REJECT xt_tcpudp dell_rbu bridge stp llc >>> ebtable_filter ebtables ip6table_filter ip6_tables iptable_filter >>> ip_tables x_tables nbd openvswitch gre vxlan libcrc32c ib_iser rdma_cm >>> iw_cm ib_cm ib_sa ib_mad ib_core ib_addr iscsi_tcp libiscsi_tcp >>> libiscsi scsi_transport_iscsi ipmi_devintf intel_rapl >>> x86_pkg_temp_thermal intel_powerclamp coretemp kvm_intel dcdbas kvm >>> crct10dif_pclmul crc32_pclmul >>> [146055.388889] ghash_clmulni_intel aesni_intel aes_x86_64 lrw >>> gf128mul dm_multipath glue_helper ablk_helper scsi_dh cryptd mei_me >>> mei lpc_ich ipmi_msghandler shpchp wmi acpi_power_meter mac_hid lp >>> parport nls_iso8859_1 igb ixgbe i2c_algo_bit dca ptp ahci pps_core >>> megaraid_sas libahci mdio [last unloaded: ipmi_si] >>> [146055.404208] CPU: 31 PID: 67922 Comm: qemu-system-x86 Not tainted >>> 3.16.0-37-generic #51~14.04.1-Ubuntu >>> [146055.409906] Hardware name: Dell Inc. PowerEdge R630/0CNCJW, BIOS >>> 1.0.4 08/28/2014 >>> [146055.415754] task: ffff883fcab69e90 ti: ffff883a1c168000 task.ti: >>> ffff883a1c168000 >>> [146055.421817] RIP: 0010:[<ffffffff810a7d31>] [<ffffffff810a7d31>] >>> set_next_entity+0x11/0xb0 >>> [146055.428079] RSP: 0018:ffff883a1c16bce8 EFLAGS: 00010092 >>> [146055.434377] RAX: 0000000000000000 RBX: 0000000000000000 RCX: >>> 00000000044aa200 >>> [146055.440913] RDX: 0000000000000000 RSI: 0000000000000000 RDI: >>> ffff883ffedf3140 >>> [146055.447474] RBP: ffff883a1c16bd00 R08: 0000000000000000 R09: >>> 0000000000000001 >>> [146055.454181] R10: 0000000000000004 R11: 0000000000000206 R12: >>> ffff883ffedf3140 >>> [146055.460968] R13: 000000000000001f R14: 0000000000000001 R15: >>> ffff883ffedf30c0 >>> [146055.467722] FS: 00007f404919d700(0000) GS:ffff883ffede0000(0000) >>> knlGS:ffff880002380000 >>> [146055.474756] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 >>> [146055.481830] CR2: 0000000000000038 CR3: 0000003a1c45b000 CR4: >>> 00000000001427e0 >>> [146055.489134] Stack: >>> [146055.496412] 0000000000000000 ffff883ffedf3140 000000000000001f >>> ffff883a1c16bd68 >>> [146055.504053] ffffffff810af2f8 ffff883ffedf3140 00000000000130c0 >>> ffff883fcab69e90 >>> [146055.511786] ffffffff8101c3b9 ffff883a1c16bd50 ffffffff810a4895 >>> ffff883fcab6a3c8 >>> [146055.519551] Call Trace: >>> [146055.527330] [<ffffffff810af2f8>] pick_next_task_fair+0x78/0x880 >>> [146055.535292] [<ffffffff8101c3b9>] ? sched_clock+0x9/0x10 >>> [146055.543379] [<ffffffff810a4895>] ? sched_clock_cpu+0x85/0xc0 >>> [146055.551519] [<ffffffff81768afb>] __schedule+0x11b/0x7a0 >>> [146055.559722] [<ffffffff81769579>] _cond_resched+0x29/0x40 >>> [146055.568020] [<ffffffffc0338289>] kvm_arch_vcpu_ioctl_run+0x3e9/0x460 [kvm] >>> [146055.576509] [<ffffffffc0321ce2>] kvm_vcpu_ioctl+0x2a2/0x5e0 [kvm] >>> [146055.585045] [<ffffffff81156952>] ? perf_event_context_sched_in+0xa2/0xc0 >>> [146055.593771] [<ffffffff811e7250>] do_vfs_ioctl+0x2e0/0x4c0 >>> [146055.602531] [<ffffffff8109dec8>] ? finish_task_switch+0x108/0x180 >>> [146055.611413] [<ffffffffc032bcd4>] ? kvm_on_user_return+0x74/0x80 [kvm] >>> [146055.620339] [<ffffffff811e74b1>] SyS_ioctl+0x81/0xa0 >>> [146055.629396] [<ffffffff8176d20d>] system_call_fastpath+0x1a/0x1f >>> [146055.638500] Code: 83 c4 10 4c 89 f2 4c 89 ee ff d0 49 8b 04 24 48 >>> 85 c0 75 e6 eb 99 0f 1f 40 00 0f 1f 44 00 00 55 48 89 e5 41 55 41 54 >>> 49 89 fc 53 <8b> 46 38 48 89 f3 85 c0 75 5d 49 8b 84 24 b0 00 00 00 48 >>> 8b 80 >>> [146055.657833] RIP [<ffffffff810a7d31>] set_next_entity+0x11/0xb0 >>> [146055.667524] RSP <ffff883a1c16bce8> >>> [146055.677082] CR2: 0000000000000038 >>> =================================== >> This looks like https://lkml.org/lkml/2015/4/3/231 > > If you're using cfs_bandwidth, it's possible (though I can't tell just > from that). If so and you can reproduce this, could you test > https://lkml.org/lkml/2015/4/6/396 (assuming it still applies at all > anyway)? I skipped you patch, I thought the issue hasn't fixed yet. Thanks for pointing on it. > If you want to provide a bunch of debugging info, rq->clock, > rq->clock_task, *cfs_rq and *se for all rqs and cgroups would be ideal, > but getting all that is kinda annoying. The most basic info would be > *cfs_rq of the crashing cpu and *cfs_rq->tg. Kirill -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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