Hi Rafael,
The warning is still there, though the detail info is a bit different.
[ 389.589955] ======================================================
[ 389.590064] [ INFO: possible circular locking dependency detected ]
[ 389.590064] 3.16.0-rc7+ #119 Not tainted
[ 389.590064] -------------------------------------------------------
[ 389.590064] kworker/u8:3/62 is trying to acquire lock:
[ 389.590064] (s_active#53){++++.+}, at: [<ffffffff811d4ad8>] kernfs_remove_by_name_ns+0x70/0x8c
[ 389.590064]
[ 389.590064] but task is already holding lock:
[ 389.590064] (cpu_hotplug.lock#2){+.+.+.}, at: [<ffffffff810628f9>] cpu_hotplug_begin+0x4f/0x79
[ 389.606161]
[ 389.606161] which lock already depends on the new lock.
[ 389.606161]
[ 389.606161]
[ 389.606161] the existing dependency chain (in reverse order) is:
[ 389.606161]
-> #3 (cpu_hotplug.lock#2){+.+.+.}:
[ 389.606161] [<ffffffff810a1081>] lock_acquire+0xdb/0x101
[ 389.606161] [<ffffffff81596187>] mutex_lock_nested+0x6d/0x37a
[ 389.606161] [<ffffffff810628f9>] cpu_hotplug_begin+0x4f/0x79
[ 389.606161] [<ffffffff81062992>] _cpu_up+0x35/0x126
[ 389.606161] [<ffffffff81062af2>] cpu_up+0x6f/0x81
[ 389.606161] [<ffffffff81d11809>] smp_init+0x53/0x93
[ 389.606161] [<ffffffff81cf5fe2>] kernel_init_freeable+0x13d/0x24b
[ 389.606161] [<ffffffff8158557a>] kernel_init+0xe/0xdf
[ 389.606161] [<ffffffff8159952c>] ret_from_fork+0x7c/0xb0
[ 389.606161]
-> #2 (cpu_hotplug.lock){++++++}:
[ 389.606161] [<ffffffff810a1081>] lock_acquire+0xdb/0x101
[ 389.606161] [<ffffffff810628eb>] cpu_hotplug_begin+0x41/0x79
[ 389.606161] [<ffffffff81062992>] _cpu_up+0x35/0x126
[ 389.606161] [<ffffffff81062af2>] cpu_up+0x6f/0x81
[ 389.606161] [<ffffffff81d11809>] smp_init+0x53/0x93
[ 389.606161] [<ffffffff81cf5fe2>] kernel_init_freeable+0x13d/0x24b
[ 389.606161] [<ffffffff8158557a>] kernel_init+0xe/0xdf
[ 389.638245] [<ffffffff8159952c>] ret_from_fork+0x7c/0xb0
[ 389.638245]
[ 389.638245] -> #1 (cpu_add_remove_lock){+.+.+.}:
[ 389.638245] [<ffffffff810a1081>] lock_acquire+0xdb/0x101
[ 389.638245] [<ffffffff81598726>] _raw_spin_lock+0x3e/0x73
[ 389.638245] [<ffffffff81590182>] get_partial_node+0x4b/0x1e7
[ 389.638245] [<ffffffff815904d8>] __slab_alloc+0x1ba/0x466
[ 389.638245] [<ffffffff81167239>] kmem_cache_alloc+0x86/0x157
[ 389.638245] [<ffffffff8117237d>] create_object+0x36/0x2a0
[ 389.638245] [<ffffffff815880df>] kmemleak_alloc+0x72/0x96
[ 389.638245] [<ffffffff81164c29>] slab_post_alloc_hook+0x28/0x2a
[ 389.638245] [<ffffffff81166f76>] kmem_cache_alloc_trace+0xf0/0x11a
[ 389.638245] [<ffffffff811923d9>] seq_open+0x37/0xac
[ 389.638245] [<ffffffff811d5511>] kernfs_fop_open+0x169/0x2ca
[ 389.638245] [<ffffffff81173822>] do_dentry_open+0x1ac/0x2ca
[ 389.638245] [<ffffffff81173c39>] finish_open+0x35/0x40
[ 389.638245] [<ffffffff81181f4c>] do_last+0x833/0x9d2
[ 389.638245] [<ffffffff81182320>] path_openat+0x235/0x4c3
[ 389.638245] [<ffffffff811828f9>] do_filp_open+0x3a/0x8a
[ 389.638245] [<ffffffff811749f3>] do_sys_open+0x70/0x102
[ 389.638245] [<ffffffff81174aa3>] SyS_open+0x1e/0x20
[ 389.638245] [<ffffffff815995d2>] system_call_fastpath+0x16/0x1b
[ 389.638245]
[ 389.638245] -> #0 (s_active#53){++++.+}:
[ 389.638245] [<ffffffff810a088a>] __lock_acquire+0xb3b/0xe41
[ 389.638245] [<ffffffff810a1081>] lock_acquire+0xdb/0x101
[ 389.638245] [<ffffffff811d3f97>] __kernfs_remove+0x169/0x2be
[ 389.638245] [<ffffffff811d4ad8>] kernfs_remove_by_name_ns+0x70/0x8c
[ 389.638245] [<ffffffff811d604c>] sysfs_remove_file_ns+0x15/0x17
[ 389.638245] [<ffffffff8138143e>] device_remove_file+0x19/0x1b
[ 389.638245] [<ffffffff813814f6>] device_remove_attrs+0x2e/0x68
[ 389.638245] [<ffffffff81381658>] device_del+0x128/0x187
[ 389.638245] [<ffffffff813816ff>] device_unregister+0x48/0x54
[ 389.638245] [<ffffffff81387366>] unregister_cpu+0x39/0x55
[ 389.638245] [<ffffffff81008c03>] arch_unregister_cpu+0x23/0x28
[ 389.638245] [<ffffffff812f7a75>] acpi_processor_remove+0x91/0xca
[ 389.638245] [<ffffffff812f51d1>] acpi_bus_trim+0x5a/0x8d
[ 389.638245] [<ffffffff812f71c6>] acpi_device_hotplug+0x301/0x3ff
[ 389.638245] [<ffffffff812f0760>] acpi_hotplug_work_fn+0x20/0x2d
[ 389.638245] [<ffffffff81078ff5>] process_one_work+0x207/0x375
[ 389.638245] [<ffffffff8107944f>] worker_thread+0x2bd/0x329
[ 389.638245] [<ffffffff8107ef6e>] kthread+0xba/0xc2
[ 389.638245] [<ffffffff8159952c>] ret_from_fork+0x7c/0xb0
[ 389.638245]
[ 389.638245] other info that might help us debug this:
[ 389.638245]
[ 389.638245] Chain exists of:
[ 389.638245] s_active#53 --> cpu_hotplug.lock --> cpu_hotplug.lock#2
[ 389.638245]
[ 389.638245] Possible unsafe locking scenario:
[ 389.638245]
[ 389.638245] CPU0 CPU1
[ 389.638245] ---- ----
[ 389.638245] lock(cpu_hotplug.lock#2);
[ 389.638245] lock(cpu_hotplug.lock);
[ 389.638245] lock(cpu_hotplug.lock#2);
[ 389.638245] lock(s_active#53);
[ 389.638245]
[ 389.638245] *** DEADLOCK ***
[ 389.638245]
[ 389.638245] 7 locks held by kworker/u8:3/62:
[ 389.638245] #0: ("kacpi_hotplug"){.+.+.+}, at: [<ffffffff81078f4d>] process_one_work+0x15f/0x375
[ 389.638245] #1: ((&hpw->work)){+.+.+.}, at: [<ffffffff81078f4d>] process_one_work+0x15f/0x375
[ 389.638245] #2: (device_hotplug_lock){+.+.+.}, at: [<ffffffff81381f7a>] lock_device_hotplug+0x17/0x19
[ 389.638245] #3: (acpi_scan_lock){+.+.+.}, at: [<ffffffff812f6ef2>] acpi_device_hotplug+0x2d/0x3ff
[ 389.638245] #4: (cpu_add_remove_lock){+.+.+.}, at: [<ffffffff81062722>] cpu_maps_update_begin+0x17/0x19
[ 389.638245] #5: (cpu_hotplug.lock){++++++}, at: [<ffffffff810628af>] cpu_hotplug_begin+0x5/0x79
[ 389.638245] #6: (cpu_hotplug.lock#2){+.+.+.}, at: [<ffffffff810628f9>] cpu_hotplug_begin+0x4f/0x79
[ 389.638245]
[ 389.638245] stack backtrace:
[ 389.638245] CPU: 1 PID: 62 Comm: kworker/u8:3 Not tainted 3.16.0-rc7+ #119
[ 389.638245] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.7.5-0-ge51488c-20140602_164612-nilsson.home.kraxel.org 04/01/2014
[ 389.638245] Workqueue: kacpi_hotplug acpi_hotplug_work_fn
[ 389.638245] ffffffff8209cc80 ffff8800372df968 ffffffff8159266c 0000000000000b3c
[ 389.638245] ffffffff820f2840 ffff8800372df9b8 ffffffff8158e0ce ffff8800372df9a8
[ 389.638245] ffffffff82486070 ffff8800372e0000 ffff8800372e09d8 ffff8800372e0000
[ 389.638245] Call Trace:
[ 389.638245] [<ffffffff8159266c>] dump_stack+0x4e/0x68
[ 389.638245] [<ffffffff8158e0ce>] print_circular_bug+0x1f8/0x209
[ 389.638245] [<ffffffff810a088a>] __lock_acquire+0xb3b/0xe41
[ 389.638245] [<ffffffff811d4ad8>] ? kernfs_remove_by_name_ns+0x70/0x8c
[ 389.638245] [<ffffffff810a1081>] lock_acquire+0xdb/0x101
[ 389.638245] [<ffffffff811d4ad8>] ? kernfs_remove_by_name_ns+0x70/0x8c
[ 389.638245] [<ffffffff811d3f97>] __kernfs_remove+0x169/0x2be
[ 389.638245] [<ffffffff811d4ad8>] ? kernfs_remove_by_name_ns+0x70/0x8c
[ 389.638245] [<ffffffff811d3412>] ? kernfs_find_ns+0xdc/0x104
[ 389.638245] [<ffffffff811d4ad8>] kernfs_remove_by_name_ns+0x70/0x8c
[ 389.638245] [<ffffffff811d604c>] sysfs_remove_file_ns+0x15/0x17
[ 389.638245] [<ffffffff8138143e>] device_remove_file+0x19/0x1b
[ 389.638245] [<ffffffff813814f6>] device_remove_attrs+0x2e/0x68
[ 389.638245] [<ffffffff81381658>] device_del+0x128/0x187
[ 389.638245] [<ffffffff813816ff>] device_unregister+0x48/0x54
[ 389.638245] [<ffffffff81387366>] unregister_cpu+0x39/0x55
[ 389.638245] [<ffffffff81008c03>] arch_unregister_cpu+0x23/0x28
[ 389.638245] [<ffffffff812f7a75>] acpi_processor_remove+0x91/0xca
[ 389.638245] [<ffffffff812f51d1>] acpi_bus_trim+0x5a/0x8d
[ 389.638245] [<ffffffff812f71c6>] acpi_device_hotplug+0x301/0x3ff
[ 389.638245] [<ffffffff812f0760>] acpi_hotplug_work_fn+0x20/0x2d
[ 389.638245] [<ffffffff81078ff5>] process_one_work+0x207/0x375
[ 389.638245] [<ffffffff81078f4d>] ? process_one_work+0x15f/0x375
[ 389.638245] [<ffffffff8107944f>] worker_thread+0x2bd/0x329
[ 389.638245] [<ffffffff81079192>] ? process_scheduled_works+0x2f/0x2f
[ 389.638245] [<ffffffff8107ef6e>] kthread+0xba/0xc2
[ 389.638245] [<ffffffff810a1511>] ? trace_hardirqs_on+0xd/0xf
[ 389.638245] [<ffffffff8107eeb4>] ? __init_kthread_worker+0x59/0x59
[ 389.638245] [<ffffffff8159952c>] ret_from_fork+0x7c/0xb0
[ 389.638245] [<ffffffff8107eeb4>] ? __init_kthread_worker+0x59/0x59
On 07/30/2014 09:12 PM, Rafael J. Wysocki wrote:
> On Wednesday, July 30, 2014 02:10:35 PM Gu Zheng wrote:
>> Hi Rafael,
>
> Hi,
>
>> A lockdep warning occurs when hot removing a cpu via sysfs:
>> echo 1 > /sys/bus/acpi/devices/LNXCPU\:02/eject
>> The kernel is latest upstream, and the test box is a kvm vm,
>> detail info as following.
>
> Well, I have a theory.
>
> Is the splat still reproducible with the patch below applied?
>
> Rafael
>
> ---
> kernel/smp.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> Index: linux-pm/kernel/smp.c
> ===================================================================
> --- linux-pm.orig/kernel/smp.c
> +++ linux-pm/kernel/smp.c
> @@ -542,6 +542,7 @@ void __init smp_init(void)
>
> idle_threads_init();
>
> + lock_device_hotplug();
> /* FIXME: This should be done in userspace --RR */
> for_each_present_cpu(cpu) {
> if (num_online_cpus() >= setup_max_cpus)
> @@ -549,6 +550,7 @@ void __init smp_init(void)
> if (!cpu_online(cpu))
> cpu_up(cpu);
> }
> + unlock_device_hotplug();
>
> /* Any cleanup work */
> smp_announce();
>
> .
>
--
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