From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753701Ab2G2VFP (ORCPT ); Sun, 29 Jul 2012 17:05:15 -0400 Received: from mail-bk0-f46.google.com ([209.85.214.46]:35287 "EHLO mail-bk0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753646Ab2G2VFN (ORCPT ); Sun, 29 Jul 2012 17:05:13 -0400 Message-ID: <5015A5A8.7030601@gmail.com> Date: Sun, 29 Jul 2012 23:05:44 +0200 From: Sasha Levin User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:13.0) Gecko/20120713 Thunderbird/13.0 MIME-Version: 1.0 To: Avi Kivity CC: paulmck@linux.vnet.ibm.com, "linux-kernel@vger.kernel.org" Subject: Re: rcu: INFO: rcu_preempt detected stalls on CPUs/tasks on v3.6 References: <500ED719.2010002@gmail.com> <50112D3B.4020201@redhat.com> <50127B16.5040401@gmail.com> <50153138.4020304@redhat.com> In-Reply-To: <50153138.4020304@redhat.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 07/29/2012 02:48 PM, Avi Kivity wrote: > On 07/27/2012 02:27 PM, Sasha Levin wrote: >> On 07/26/2012 01:42 PM, Avi Kivity wrote: >>> On 07/24/2012 08:10 PM, Sasha Levin wrote: >>>> [ 215.026612] NMI backtrace for cpu 1 >>>> [ 215.026612] CPU 1 >>>> [ 215.026612] Pid: 2395, comm: pageattr-test Tainted: G W 3.5.0-sasha-01644-g824681b #267 >>>> [ 215.026612] RIP: 0010:[] [] native_write_msr_safe+0xa/0x10 >>>> [ 215.026612] RSP: 0018:ffff88001b803f70 EFLAGS: 00000046 >>>> [ 215.026612] RAX: 0000000000000000 RBX: 000000000000ef80 RCX: 000000000000080b >>>> [ 215.026612] RDX: 0000000000000000 RSI: 0000000000000000 RDI: 000000000000080b >>>> [ 215.026612] RBP: ffff88001b803f70 R08: 00003ffffffff000 R09: ffff880000000000 >>>> [ 215.026612] R10: 0000000000000001 R11: 0000000000000000 R12: 0000000000000000 >>>> [ 215.026612] R13: ffff880007a98000 R14: ffff88001fc3a4b8 R15: ffff880000000000 >>>> [ 215.026612] FS: 0000000000000000(0000) GS:ffff88001b800000(0000) knlGS:0000000000000000 >>>> [ 215.026612] CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b >>>> [ 215.026612] CR2: 000000000000000c CR3: 0000000019dcf000 CR4: 00000000000406e0 >>>> [ 215.026612] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 >>>> [ 215.026612] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400 >>>> [ 215.026612] Process pageattr-test (pid: 2395, threadinfo ffff88000ced0000, task ffff88000d773000) >>>> [ 215.026612] Stack: >>>> [ 215.026612] ffff88001b803f88 ffffffff81095d07 000000000000ef80 ffff88001b803fa8 >>>> [ 215.026612] ffffffff810901c4 ffff88000ced1db0 0000000000007a98 ffff88000ced1d00 >>>> [ 215.026612] ffffffff8369c4af ffff88000ced1c78 ffff88000ced1d00 ffffffff8369aeb4 >>>> [ 215.026612] Call Trace: >>>> [ 215.026612] >>>> [ 215.026612] [] native_apic_msr_eoi_write+0x27/0x30 >>>> [ 215.026612] [] smp_apic_timer_interrupt+0x34/0xa0 >>>> [ 215.026612] [] apic_timer_interrupt+0x6f/0x80 >>>> [ 215.026612] >>>> [ 215.026612] [] ? retint_restore_args+0x13/0x13 >>>> [ 215.026612] [] ? lookup_address+0x112/0x170 >>>> [ 215.026612] [] print_split+0x7e/0x200 >>>> [ 215.026612] [] pageattr_test+0x80/0x4a0 >>>> [ 215.026612] [] ? trace_hardirqs_on_caller+0x118/0x140 >>>> [ 215.026612] [] ? schedule_timeout+0x2ce/0x370 >>>> [ 215.026612] [] ? retint_restore_args+0x13/0x13 >>>> [ 215.026612] [] ? pageattr_test+0x4a0/0x4a0 >>>> [ 215.026612] [] do_pageattr_test+0x1f/0x50 >>>> [ 215.026612] [] kthread+0xad/0xc0 >>>> [ 215.026612] [] kernel_thread_helper+0x4/0x10 >>>> [ 215.026612] [] ? retint_restore_args+0x13/0x13 >>>> [ 215.026612] [] ? kthread_flush_work_fn+0x10/0x10 >>>> [ 215.026612] [] ? gs_change+0x13/0x13 >>>> [ 215.026612] Code: 00 55 89 f9 48 89 e5 0f 32 45 31 c0 89 c7 48 89 d0 44 89 06 48 c1 e0 20 89 f9 5d 48 09 c8 c3 66 90 55 89 f0 89 f9 48 89 e5 0f 30 <31> c0 5d c3 66 90 55 89 f9 48 89 e5 0f 33 89 c7 48 89 d0 5d 48 >>> >>> This is immediately after the EOI. It looks like the timer interrupt is >>> stuck somehow. Can you run kvm_stat and confirm? >> >> Yup, looks like it. kvm_stats is something like this: >> >> kvm_entry 142104033 939393 >> kvm_exit 142104004 939390 >> kvm_apic 84781115 582714 >> kvm_msr 84682085 582714 >> kvm_apic_accept_irq 65219959 522263 >> kvm_inj_virq 43173709 291385 >> >> With everything else at 0 when it happens. > > Please run a trace and verify that the injected vector is indeed the > timer interrupt. Looks like it is. > Then work backwards to see the last place it is > programmed (APIC_TMICT/APIC_TDCR). This looks like what you're looking for: kvm_apic: apic_write APIC_TMICT = 0x3e Basically it's spinning on the following 4 lines of trace when it happens: 16063.549189: kvm_apic: apic_write APIC_TMICT = 0x3e 16063.549190: kvm_msr: msr_write 838 = 0x3e 16063.549190: kvm_exit: reason EXTERNAL_INTERRUPT rip 0xffffffff8115de02 info 0 0 16063.549190: kvm_entry: vcpu 2