From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:37440) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZQgRF-0000yn-UK for qemu-devel@nongnu.org; Sat, 15 Aug 2015 14:44:18 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ZQgR9-0007PF-Hv for qemu-devel@nongnu.org; Sat, 15 Aug 2015 14:44:17 -0400 Received: from mail-ph.de-nserver.de ([85.158.179.214]:14446) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZQgR9-0007Nv-7P for qemu-devel@nongnu.org; Sat, 15 Aug 2015 14:44:11 -0400 From: Stefan Priebe Message-ID: <55CF8877.30802@profihost.ag> Date: Sat, 15 Aug 2015 20:44:07 +0200 MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Subject: [Qemu-devel] guest: NO_HZ FULL will not work with unstable sched clock List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel Hi, while switching to a FULL tickless kernel i detected that all our VMs produce the following stack trace while running under qemu 2.3.0. [ 0.195160] HPET: 3 timers in total, 0 timers will be used for per-cpu timer [ 0.195181] hpet0: at MMIO 0xfed00000, IRQs 2, 8, 0 [ 0.195188] hpet0: 3 comparators, 64-bit 100.000000 MHz counter [ 0.200119] Switched to clocksource hpet [ 0.201164] ------------[ cut here ]------------ [ 0.201193] WARNING: CPU: 1 PID: 1 at kernel/time/tick-sched.c:192 can_stop_full_tick+0x1c1/0x200() [ 0.201199] NO_HZ FULL will not work with unstable sched clock [ 0.201203] Modules linked in: [ 0.201214] CPU: 1 PID: 1 Comm: swapper/0 Not tainted 3.18.20+55-ph #1 [ 0.201219] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.8.1-0-g4adadbd-20150316_085822-nilsson.home.kraxel.org 04/01/2014 [ 0.201226] 0000000000000009 ffff88023fc43e88 ffffffff815f5889 00000000000008df [ 0.201230] ffff88023fc43ed8 ffff88023fc43ec8 ffffffff8107433c ffff88023fc43ea8 [ 0.201233] 0000000000000000 0000000000000001 ffff880236c41300 00000000cbbde78b [ 0.201237] Call Trace: [ 0.201240] [] dump_stack+0x46/0x58 [ 0.201260] [] warn_slowpath_common+0x8c/0xc0 [ 0.201264] [] warn_slowpath_fmt+0x46/0x50 [ 0.201270] [] can_stop_full_tick+0x1c1/0x200 [ 0.201274] [] tick_nohz_irq_exit+0x97/0xd0 [ 0.201277] [] irq_exit+0xcd/0x130 [ 0.201286] [] smp_apic_timer_interrupt+0x4a/0x60 [ 0.201293] [] apic_timer_interrupt+0x6a/0x70 [ 0.201296] [] ? __d_lookup+0x55/0x160 [ 0.201309] [] d_lookup+0x35/0x60 [ 0.201312] [] lookup_dcache+0x3b/0xd0 [ 0.201315] [] __lookup_hash+0x23/0x50 [ 0.201319] [] lookup_one_len+0xce/0x120 [ 0.201328] [] __create_file+0x8f/0x260 [ 0.201332] [] debugfs_create_dir+0x1b/0x20 [ 0.201338] [] event_create_dir+0x68/0x520 [ 0.201342] [] event_trace_init+0x188/0x210 [ 0.201348] [] ? trace_create_file+0x1b/0x50 [ 0.201352] [] ? event_trace_enable+0x1a2/0x1a2 [ 0.201359] [] do_one_initcall+0xd8/0x200 [ 0.201368] [] ? parse_args+0x1f0/0x470 [ 0.201373] [] ? __wake_up+0x53/0x70 [ 0.201378] [] kernel_init_freeable+0x168/0x1ff [ 0.201381] [] ? do_early_param+0x8c/0x8c [ 0.201389] [] ? cryptomgr_probe+0x60/0xe0 [ 0.201398] [] ? rest_init+0x80/0x80 [ 0.201401] [] kernel_init+0xe/0xf0 [ 0.201405] [] ret_from_fork+0x58/0x90 [ 0.201408] [] ? rest_init+0x80/0x80 [ 0.201415] ---[ end trace a15ba3bc1d247b4c ]--- Stefan