On Fri, 2012-02-10 at 15:36 +0530, Srivatsa S. Bhat wrote: > >>> [ 32.448626] ------------[ cut here ]------------ > >>> [ 32.449160] WARNING: at arch/x86/kernel/smp.c:119 native_smp_send_reschedule+0x25/0x43() > >>> [ 32.449621] Pid: 1, comm: init_stage2 Not tainted 3.2.0+ #14 > >>> [ 32.449621] Call Trace: > >>> [ 32.449621] <IRQ> [<ffffffff81041a44>] ? native_smp_send_reschedule+0x25/0x43 > >>> [ 32.449621] [<ffffffff810735b2>] warn_slowpath_common+0x7b/0x93 > >>> [ 32.449621] [<ffffffff810962cc>] ? tick_nohz_handler+0xc9/0xc9 > >>> [ 32.449621] [<ffffffff81073675>] warn_slowpath_null+0x15/0x18 > >>> [ 32.449621] [<ffffffff81041a44>] native_smp_send_reschedule+0x25/0x43 > >>> [ 32.449621] [<ffffffff81067a00>] smp_send_reschedule+0xa/0xc > >>> [ 32.449621] [<ffffffff8106f25e>] scheduler_tick+0x21a/0x242 > >>> [ 32.449621] [<ffffffff8107da10>] update_process_times+0x62/0x73 > >>> [ 32.449621] [<ffffffff81096336>] tick_sched_timer+0x6a/0x8a > >>> [ 32.449621] [<ffffffff8108c5eb>] __run_hrtimer.clone.26+0x55/0xcb > >>> [ 32.449621] [<ffffffff8108cd77>] hrtimer_interrupt+0xcb/0x19b > >>> [ 32.449621] [<ffffffff810428a8>] smp_apic_timer_interrupt+0x72/0x85 > >>> [ 32.449621] [<ffffffff8165a8de>] apic_timer_interrupt+0x6e/0x80 > >>> [ 32.449621] <EOI> [<ffffffff8165928e>] ? _raw_spin_unlock_irqrestore+0x3a/0x3e > >>> [ 32.449621] [<ffffffff81042f4e>] ? arch_local_irq_restore+0x6/0xd > >>> [ 32.449621] [<ffffffff810430c4>] default_send_IPI_mask_allbutself_phys+0x78/0x88 > >>> [ 32.449621] [<ffffffff8106c3c4>] ? __migrate_task+0xf1/0xf1 > >>> [ 32.449621] [<ffffffff81045445>] physflat_send_IPI_allbutself+0x12/0x14 > >>> [ 32.449621] [<ffffffff81041aaf>] native_stop_other_cpus+0x4d/0xa8 > >>> [ 32.449621] [<ffffffff810411c6>] native_machine_shutdown+0x56/0x6d > >>> [ 32.449621] [<ffffffff81048499>] kvm_shutdown+0x1a/0x1c > >>> [ 32.449621] [<ffffffff810411f9>] machine_shutdown+0xa/0xc > >>> [ 32.449621] [<ffffffff81041265>] native_machine_restart+0x20/0x32 > >>> [ 32.449621] [<ffffffff81041297>] machine_restart+0xa/0xc > >>> [ 32.449621] [<ffffffff81081d53>] kernel_restart+0x49/0x4d > >>> [ 32.449621] [<ffffffff81081f26>] sys_reboot+0x14b/0x18a > >>> [ 32.449621] [<ffffffff81089937>] ? remove_wait_queue+0x4c/0x51 > >>> [ 32.449621] [<ffffffff8107637f>] ? do_wait+0x1a4/0x1e7 > >>> [ 32.449621] [<ffffffff8107735a>] ? sys_wait4+0xa8/0xbc > >>> [ 32.449621] [<ffffffff8107522b>] ? clear_tsk_thread_flag+0xf/0xf > >>> [ 32.449621] [<ffffffff81659a25>] ? async_page_fault+0x25/0x30 > >>> [ 32.449621] [<ffffffff81659e92>] system_call_fastpath+0x16/0x1b > >>> [ 32.449621] ---[ end trace d0f03651493fd3d6 ]-- OK, so a 'modern' kernel does it slightly different and I've no idea what exactly goes wrong in your vintage version. But I can see the current stuff going at it all wrong. What seems to happen is that native_nmi_stop_other_cpus() NMI broadcasts for smp_stop_nmi_callback()->stop_this_cpu(). Which without any serialization what so ever marks all remote CPUs offline and calls halt with IRQs disabled -> dead. While we're waiting for this all to complete, the scheduler tries to no_hz load-balance and kick a cpu it thinks is still around and we get the above splat because the NMI just marked it offline without telling anybody about it. Now, arguably you don't want to go through the whole hotplug crap to shut down your machine, esp not on panic, but clearing the online state without telling anybody about it is bound to lead to these things. No immediate solution comes to mind... -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
