Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751178AbcCWEuY (ORCPT ); Wed, 23 Mar 2016 00:50:24 -0400 Received: from mail-wm0-f43.google.com ([74.125.82.43]:36248 "EHLO mail-wm0-f43.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750716AbcCWEuS (ORCPT ); Wed, 23 Mar 2016 00:50:18 -0400 Message-ID: <1458708614.14170.11.camel@gmail.com> Subject: Re: rcu stalls and soft lockups with recent kernels From: Mike Galbraith To: Ion Badulescu , linux-kernel@vger.kernel.org Cc: "Paul E. McKenney" Date: Wed, 23 Mar 2016 05:50:14 +0100 In-Reply-To: <56F1A995.4000006@badula.org> References: <56B39F0C.7070406@badula.org> <56B3A2A8.6000302@badula.org> <56E9868E.4000006@badula.org> <1458268137.3859.5.camel@gmail.com> <56F1A995.4000006@badula.org> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.16.5 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4834 Lines: 105 (cc) On Tue, 2016-03-22 at 16:22 -0400, Ion Badulescu wrote: > On 03/17/2016 10:28 PM, Mike Galbraith wrote: > > On Wed, 2016-03-16 at 12:15 -0400, Ion Badulescu wrote: > > > Just following up to my own email: > > > > > > It turns out that we can eliminate the RCU stalls by changing from > > > CONFIG_RCU_NOCB_CPU_ALL to CONFIG_RCU_NOCB_CPU_NONE. Letting each cpu > > > handle its own RCU callbacks completely fixes the problems for us. > > > > > > Now, CONFIG_NO_HZ_FULL and CONFIG_RCU_NOCB_CPU_ALL is the default config > > > for fedora and rhel7. Ho-humm... > > > > All RCU offloaded to CPU0 of a big box seems like a very bad idea. > > > It's not offloaded to CPU0, is it? Those rcuo* threads are not cpu-bound > and can run on any cpu the scheduler will put them on. In any case, > there was no indication that the rcuo* threads wanted to run but > couldn't get cpu time. Right, my thinker was screwed on cross-threaded. > Anyway, looks like I spoke too soon. It's less often with > RCU_NOCB_CPU_NONE than with RCU_NOCB_CPU_ALL, but the soft lockups and > rcu stalls are still happening. > > [44206.316711] clocksource: timekeeping watchdog: Marking clocksource > 'tsc' as unstable because the skew is too large: > [44206.328463] clocksource: 'hpet' wd_now: > ffffffff wd_last: 5f03cdca mask: ffffffff > [44206.339037] clocksource: 'tsc' cs_now: > 64788b443c3a cs_last: 647840eea919 mask: ffffffffffffffff > [44206.351253] clocksource: Switched to clocksource hpet > [44922.301452] INFO: rcu_sched detected stalls on CPUs/tasks: > [44922.307644] 0-...: (1 GPs behind) idle=53d/140000000000001/0 > softirq=8515474/8515477 fqs=6994 > [44922.317435] (detected by 1, t=21019 jiffies, g=2011397, c=2011396, > q=3263) > [44922.325274] Task dump for CPU 0: > [44922.325276] python R running task 0 257113 257112 > 0x00080088 0 FAIR 1 0 152294 48373 > [44922.325283] ffffffff8152ca8e ffff881b76870000 ffff880e83669000 > 0000000000007d54 > [44922.333671] ffff881b1cdc7a48 ffff880a58a57e58 0000000000000086 > 0000000000000000 > [44922.342060] 0000000000000000 0000000000003fa1 ffff880a58a54000 > ffff880a58a57e88 > [44922.350446] Call Trace: > [44922.353215] [] ? __schedule+0x38e/0xa90 > [44922.359388] [] ? rcu_eqs_enter_common+0x66/0x130 > [44922.366437] [] ? acct_account_cputime+0x1c/0x20 > [44922.373388] [] ? account_user_time+0x78/0x80 > [44922.380045] [] ? vtime_account_user+0x43/0x60 > [44922.386801] [] ? __context_tracking_exit+0x70/0xc0 > [44922.394044] [] ? enter_from_user_mode+0x1f/0x50 > [44922.400994] [] ? apic_timer_interrupt+0x69/0x90 > [44923.210453] NMI watchdog: BUG: soft lockup - CPU#0 stuck for 21s! > [python:257113] > [44923.218890] Modules linked in: nfsv3 nfs_acl nfs msr autofs4 lockd > grace sunrpc cachefiles fscache binfmt_misc nls_iso8859_1 nls_cp437 vfat > fat vhost_net vhost tun kvm irqbypass input_leds hid_generic iTCO_wdt > iTCO_vendor_support pcspkr sfc mtd i2c_algo_bit sb_edac sg l > pc_ich mfd_core ehci_pci ehci_hcd xhci_pci xhci_hcd i2c_i801 i2c_core > ixgbe ptp pps_core mdio ipmi_devintf ipmi_si ipmi_msghandler tpm_tis tpm > acpi_power_meter hwmon ext4 jbd2 mbcache crc16 raid1 dm_mirror > dm_region_hash dm_log dm_mod > [44923.269289] CPU: 0 PID: 257113 Comm: python Tainted: G I > 4.4.5-el6.ia32e.lime.0 #1 > [44923.279089] Hardware name: Intel Corporation S2600WTT/S2600WTT, BIOS > SE5C610.86B.01.01.0011.081020151200 08/10/2015 > [44923.290824] task: ffff880e83669000 ti: ffff880a58a54000 task.ti: > ffff880a58a54000 > [44923.299253] RIP: 0033:[<00002b5ee4e0502d>] [<00002b5ee4e0502d>] > 0x2b5ee4e0502d > [44923.307508] RSP: 002b:00007ffe4120b170 EFLAGS: 00000212 > [44923.313494] RAX: 0000000000000008 RBX: 0000000003fe1480 RCX: > 0000000003fc9b00 > [44923.321513] RDX: 00002b5ee34b4260 RSI: 0000000000002248 RDI: > 00000000000000d4 > [44923.329530] RBP: 0000000003fe1800 R08: 0000000000000078 R09: > 0000000000000800 > [44923.337548] R10: 00007ffe4120b550 R11: 0000000000011240 R12: > 00002b5ee34ba938 > [44923.345566] R13: 00002b5ee34c1010 R14: 00007ffe4120b428 R15: > 0000000000000400 > [44923.353580] FS: 00002b5ec7fe98c0(0000) GS:ffff88103fc00000(0000) > knlGS:0000000000000000 > [44923.362689] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > [44923.369147] CR2: 00002b5ee4190000 CR3: 00000005ac81b000 CR4: > 00000000001406f0 > > That rcu_eqs_enter_common function seems to be a fairly common > occurrence in these stack traces. Not sure if it means anything, though. > > Also, this seems to be a sock lockup with RIP in userspace. Does it mean > timer interrupts are disabled? Somehow it fails to reschedule the NMI timer. > > We're at our wits' end here... > > This, btw, is a 2x12 core Haswell box. > > Thanks, > -Ion