2013/5/21 Steven Rostedt <rost...@goodmis.org>: > commit a382bf934449 "nohz: Assign timekeeping duty to a CPU outside the > full dynticks range" added a cpu notifier callback that would prevent > the time keeping CPU from going offline if the have_nohz_full_mask was > set. > > This also prevents the CPU from going offline on system reboot. > > Worse yet, the return code was -EINVAL, but the notifier does not > recognize error codes, and it must be wrapped by a notifier_from_errno() > function. This means that even though the CPU would fail to go down, the > notifier would think it succeeded, and the cpu down process would > continue. > > This caused two different problems. One, the migration thread after > moving tasks from the CPU would park itself and then a task, namely the > reboot task, could migrate onto that CPU. Then the reboot task spins > waiting for the cpu to go idle. But because the reboot task happens to > be spinning on the cpu its waiting for, the system hangs. > > The other error that happened was that the sched_domain re-setup would > get confused, and in get_group() the cpu = cpumask_first() would process > a mask that had nothing set, and return cpu > nr_cpu_ids. Later it would > reference the per_cpu sg with this CPU and get a bogus pointer and > crash. > > This fix simply fixes the issue with the return code of the cpu > notifier. This prevents all non-boot CPUs from going down, but that only > gives us the following warnings and does not crash or lockup the system. > > [ 73.655698] _cpu_down: attempt to take down CPU 2 failed > [ 73.661874] Error taking CPU2 down: -22 > [ 73.665727] Non-boot CPUs are not disabled > [ 73.669853] Restarting system. > > And because of this, we get this warning too. But at least the system > reboots. > > [ 73.432740] ------------[ cut here ]------------ > [ 73.433003] WARNING: at > /home/rostedt/work/git/linux-trace.git/kernel/workqueue.c:4584 > workqueue_cpu_up_callback+0x24b/0x48c() > [ 73.433003] Modules linked in: ebtables ipt_MASQUERADE sunrpc bridge stp > llc ip6t_REJECT nf_conntrack_ipv6 nf_defrag_ipv6 ipv6 uinput > snd_hda_codec_idt snd_hda_intel snd_hda_codec kvm_intel kvm snd_hwdep snd_seq > snd_seq_device snd_pcm snd_timer snd soundcore snd_page_alloc shpchp i2c_i801 > microcode pata_acpi firewire_ohci firewire_core crc_itu_t ata_generic i915 > drm_kms_helper drm i2c_algo_bit i2c_core video [last unloaded: ip6_tables] > [ 73.433003] CPU: 0 PID: 2765 Comm: reboot Not tainted 3.10.0-rc2-test+ #124 > [ 73.433003] Hardware name: To Be Filled By O.E.M. To Be Filled By > O.E.M./To be filled by O.E.M., BIOS SDBLI944.86P 05/08/2007 > [ 73.433003] ffffffff817d0b08 ffff88006a95bc28 ffffffff814ca368 > ffff88006a95bc68 > [ 73.433003] ffffffff81035267 0000000000000002 0000000000000000 > ffff88007d512e00 > [ 73.433003] 0000000000000002 ffff88007a809cc0 ffff88007d513260 > ffff88006a95bc78 > [ 73.433003] Call Trace: > [ 73.433003] [<ffffffff814ca368>] dump_stack+0x19/0x1b > [ 73.433003] [<ffffffff81035267>] warn_slowpath_common+0x67/0x80 > [ 73.433003] [<ffffffff8103529a>] warn_slowpath_null+0x1a/0x1c > [ 73.433003] [<ffffffff814bee83>] workqueue_cpu_up_callback+0x24b/0x48c > [ 73.433003] [<ffffffff810679fd>] ? cpumask_weight+0x13/0x14 > [ 73.433003] [<ffffffff814d22dd>] notifier_call_chain+0x37/0x63 > [ 73.433003] [<ffffffff8105c19a>] __raw_notifier_call_chain+0xe/0x10 > [ 73.433003] [<ffffffff810383d8>] __cpu_notify+0x20/0x32 > [ 73.433003] [<ffffffff814b3122>] _cpu_down+0x90/0x229 > [ 73.433003] [<ffffffff81038687>] disable_nonboot_cpus+0x5a/0xfb > [ 73.433003] [<ffffffff81049d87>] kernel_restart+0x18/0x5a > [ 73.433003] [<ffffffff81049f52>] SYSC_reboot+0x177/0x1d9 > [ 73.433003] [<ffffffff810ca70a>] ? trace_preempt_on+0x1b/0x2f > [ 73.433003] [<ffffffff81085eac>] ? trace_hardirqs_on+0xd/0xf > [ 73.433003] [<ffffffff810e571e>] ? user_exit+0x69/0x70 > [ 73.433003] [<ffffffff810e571e>] ? user_exit+0x69/0x70 > [ 73.433003] [<ffffffff81085e68>] ? trace_hardirqs_on_caller+0x160/0x197 > [ 73.433003] [<ffffffff81085eac>] ? trace_hardirqs_on+0xd/0xf > [ 73.433003] [<ffffffff8100c7b7>] ? syscall_trace_enter+0xdb/0x1b3 > [ 73.433003] [<ffffffff81049fc2>] SyS_reboot+0xe/0x10 > [ 73.433003] [<ffffffff814d5814>] tracesys+0xdd/0xe2 > [ 73.433003] ---[ end trace 1a5fc10dcbddf506 ]--- > > Signed-off-by: Steven Rostedt <rost...@goodmis.org>
There has been this patch that makes it return -EPERM instead: https://lkml.org/lkml/2013/5/20/386 Not sure which is best. Both sort of make sense to me. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
