From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756687Ab2GCP1S (ORCPT ); Tue, 3 Jul 2012 11:27:18 -0400 Received: from mx1.redhat.com ([209.132.183.28]:32271 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752181Ab2GCP1Q (ORCPT ); Tue, 3 Jul 2012 11:27:16 -0400 Message-ID: <4FF30F48.3030702@redhat.com> Date: Tue, 03 Jul 2012 11:27:04 -0400 From: Prarit Bhargava User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.17) Gecko/20110419 Red Hat/3.1.10-1.el6_0 Thunderbird/3.1.10 MIME-Version: 1.0 To: John Stultz CC: Linux Kernel , stable@vger.kernel.org, Thomas Gleixner Subject: Re: [PATCH 0/3][RFC] Potential fix for leapsecond caused futex issue (v3) References: <1341281766-22722-1-git-send-email-johnstul@us.ibm.com> <4FF28CB1.7020304@us.ibm.com> In-Reply-To: <4FF28CB1.7020304@us.ibm.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 07/03/2012 02:09 AM, John Stultz wrote: > On 07/02/2012 07:16 PM, John Stultz wrote: >> NOTE: Some reports have been of a hard hang right at or before >> the leapsecond. I've not been able to reproduce or diagnose >> this, so this fix does not likely address the reported hard >> hangs (unless they end up being connected to the futex/hrtimer >> issue). Please email lkml and me if you experienced this. > > Since as noted above, I've seen some sporadic reports of hard hangs. Some seem > connected to the hrtimer problem, where ksoftirq seems to go crazy and cause nmi > watchdog lockups, but others are less clear. > > I wanted to try to provide a way to stress both the kernel's leapsecond code as > well as provide a way for folks to be able to test their application's > robustness in the face of leapsecond inconsistencies. > > Attached is my first attempt at such a test. > > It is designed to be run on a server, where it will schedule a leapsecond every > day at midnight GMT. So every day, while it runs, the server will see a > leapsecond. This allows the the leap second, as well as any suspected timer > related lockups that might happen when the leapsecond is scheduled to be stressed. > > The test also outputs time samples right before, during and after the leapsecond > is applied, so you can watch it happen. > > Also since once a day is a fairly low frequency, if you pass a "-s" to the test, > it will jump the system time forward to 10 seconds right before the scheduled > leapsecond for that day. Allowing a leapsecond to occur every ~13 seconds. This > mode may cause application disruption, as it also causes the system to advance a > day every ~13 seconds. > > The test additionally will note if it observes the hrtimer early expiration > problem that was widely seen over the weekend. > > Hopefully this will provide a mechanism to test and maintain the kernel's > correct behaviour for these rare events, as well as allowing folks to get more > comfortable with leapsecond behaviour and test how it might impact their > applications. > > If anyone who observed a hard hang is able to use this to reproduce the problem, > I'd greatly like to hear about it. > > Build instructions are in the test file. Thanks John -- I moved to using this for testing and hit the following softlockup when running latest + your patchset: [ 1084.433362] BUG: soft lockup - CPU#17 stuck for 22s! [leap-a-day:1275]^M [ 1084.440700] Modules linked in: nfs nfs_acl auth_rpcgss fscache lockd sunrpc kvm_intel ixgbe coretemp kvm igb ptp pps_core mdio ioatdma lpc_ich crc32c_intel joydev mfd_core i2c_i801 ghash_clmulni_intel tpm_tis wmi dca sb_edac microcode edac_core pcspkr tpm tpm_bios hid_generic isci libsas scsi_transport_sas mgag200 i2c_algo_bit drm_kms_helper ttm drm i2c_core [last unloaded: scsi_wait_scan]^M [ 1084.479183] CPU 17 ^M [ 1084.481568] Modules linked in: nfs nfs_acl auth_rpcgss fscache lockd sunrpc kvm_intel ixgbe coretemp kvm igb ptp pps_core mdio ioatdma lpc_ich crc32c_intel joydev mfd_core i2c_i801 ghash_clmulni_intel tpm_tis wmi dca sb_edac microcode edac_core pcspkr tpm tpm_bios hid_generic isci libsas scsi_transport_sas mgag200 i2c_algo_bit drm_kms_helper ttm drm i2c_core [last unloaded: scsi_wait_scan]^M [ 1084.520061] ^M [ 1084.521740] Pid: 1275, comm: leap-a-day Not tainted 3.5.0-rc4+ #1 Intel Corporation S2600CP/S2600CP^M [ 1084.531860] RIP: 0010:[] [] smp_call_function_many+0x1f7/0x260^M [ 1084.541962] RSP: 0018:ffff88042769fdf8 EFLAGS: 00000202^M [ 1084.547891] RAX: 0000000000000080 RBX: 0000000000000292 RCX: 0000000000000020^M [ 1084.555858] RDX: 0000000000000080 RSI: 0000000000000080 RDI: 0000000000000292^M [ 1084.563826] RBP: ffff88042769fe48 R08: ffffffff81cd7200 R09: 0000000000000080^M [ 1084.571790] R10: ffff88042f7342f0 R11: 0000000000000216 R12: ffffffff8137cd43^M [ 1084.579758] R13: ffff88042769fd88 R14: 0000000000000292 R15: ffff88042769fda8^M [ 1084.587727] FS: 00007fba8d48b740(0000) GS:ffff88042f720000(0000) knlGS:0000000000000000^M [ 1084.596758] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033^M [ 1084.603174] CR2: 0000003d72e18c48 CR3: 0000000415d66000 CR4: 00000000000407e0^M [ 1084.611141] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000^M [ 1084.619120] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400^M [ 1084.627092] Process leap-a-day (pid: 1275, threadinfo ffff88042769e000, task ffff880425fd1720)^M [ 1084.636694] Stack:^M [ 1084.638950] 0000000000000003 0100000000000019 0000000000000000 ffffffff8107e960^M [ 1084.647211] ffff88042769fe58 ffff88042769ff58 ffffffff8107e960 0000000000000000^M [ 1084.655479] 0000000000000000 0000000000000000 ffff88042769fe58 ffffffff810b3f12^M [ 1084.663723] Call Trace:^M [ 1084.666466] [] ? hrtimer_wakeup+0x30/0x30^M [ 1084.672784] [] ? hrtimer_wakeup+0x30/0x30^M [ 1084.679107] [] smp_call_function+0x22/0x30^M [ 1084.685530] [] on_each_cpu+0x28/0x70^M [ 1084.691371] [] do_clock_was_set+0x1c/0x30^M [ 1084.697691] [] clock_was_set+0x55/0x60^M [ 1084.703732] [] do_settimeofday+0xd3/0xe0^M [ 1084.709971] [] do_sys_settimeofday+0xb5/0x110^M [ 1084.716677] [] sys_settimeofday+0x83/0xb0^M [ 1084.723012] [] system_call_fastpath+0x16/0x1b^M [ 1084.729782] Code: f7 ff 15 95 89 b6 00 80 7d bf 00 0f 84 9c fe ff ff 41 f6 47 20 01 0f 84 91 fe ff ff 0f 1f 84 00 00 00 00 00 f3 90 41 f6 47 20 01 <75> f7 e9 7b fe ff ff 66 90 4c 89 e2 4c 89 ee 89 df e8 53 8b 21 ^M I'm taking a look now ... I'm not sure I believe the hrtimer_wakeup() calls on the stack. P. > > thanks > -john