Re: [PATCH 2/4] memory-hotplug: add node_device_release
From: Yasuaki Ishimatsu
Date: Thu Oct 04 2012 - 21:01:33 EST
Hi Kosaki-san,
2012/10/02 3:12, KOSAKI Motohiro wrote:
On Mon, Oct 1, 2012 at 2:54 AM, Yasuaki Ishimatsu
<isimatu.yasuaki@xxxxxxxxxxxxxx> wrote:
Hi Kosaki-san,
2012/09/29 7:19, KOSAKI Motohiro wrote:
I don't understand it. How can we get rid of the warning?
See cpu_device_release() for example.
If we implement a function like cpu_device_release(), the warning
disappears. But the comment says in the function "Never copy this
way...".
So I think it is illegal way.
What does "illegal" mean?
The "illegal" means the code should not be mimicked.
You still haven't explain any benefit of your code. If there is zero
benefit, just kill it.
I believe everybody think so.
Again, Which benefit do you have?
The patch has a benefit to delets a warning message.
Why do we need this node_device_release() implementation?
I think that this is a manner of releasing object related kobject.
No. Usually we never call memset() from release callback.
What we want to release is a part of array, not a pointer.
Therefore, there is only this way instead of kfree().
Why? Before your patch, we don't have memset() and did work it.
If we does not apply the patch, a warning message is shown.
So I think it did not work well.
I can't understand what mean "only way".
For deleting a warning message, I created a node_device_release().
In the manner of releasing kobject, the function frees a object related
to the kobject. So most functions calls kfree() for releasing it.
In node_device_release(), we need to free a node struct. If the node
struct is pointer, I can free it by kfree. But the node struct is a part
of node_devices[] array. I cannot free it. So I filled the node struct
with 0.
But you think it is not good. Do you have a good solution?
Do nothing. just add empty release function and kill a warning.
Obviously do nothing can't make any performance drop nor any
side effect.
meaningless memset() is just silly from point of cache pollution view.
I have the reason to have to fill the node struct with 0 by memset.
The node is a part of node struct array (node_devices[]).
If we add empty release function for suppressing warning,
some data remains in the node struct after hot removing memory.
So if we re-hot adds the memory, the node struct is reused by
register_onde_node(). But the node struct has some data, because
it was not initialized with 0. As a result, more waning is shown
by the remained data at hot addinig memory as follows:
[ 374.037710] kobject (ffffffff82c15718): tried to init an initialized object, something is seriously wrong.
[ 374.153169] Pid: 4, comm: kworker/0:0 Tainted: G W 3.6.0 #5
[ 374.230279] Call Trace:
[ 374.259647] [<ffffffff8133cf39>] kobject_init+0x89/0xa0
[ 374.323286] [<ffffffff8143632c>] device_initialize+0x2c/0xc0
[ 374.392086] [<ffffffff814376a6>] device_register+0x16/0x30
[ 374.458856] [<ffffffff81449b15>] register_node+0x25/0xe0
[ 374.523434] [<ffffffff8144a057>] register_one_node+0x67/0x140
[ 374.593306] [<ffffffff81652e40>] add_memory+0x100/0x1f0
[ 374.656961] [<ffffffffa00a31c6>] acpi_memory_enable_device+0x92/0xdf [acpi_memhotplug]
[ 374.752811] [<ffffffffa00a3753>] acpi_memory_device_add+0x10d/0x116 [acpi_memhotplug]
[ 374.847622] [<ffffffff813a4376>] acpi_device_probe+0x50/0x18a
[ 374.917504] [<ffffffff8124b053>] ? sysfs_create_link+0x13/0x20
[ 374.988426] [<ffffffff81439d7c>] really_probe+0x6c/0x320
[ 375.053061] [<ffffffff8143a077>] driver_probe_device+0x47/0xa0
[ 375.123922] [<ffffffff8143a180>] ? __driver_attach+0xb0/0xb0
[ 375.192709] [<ffffffff8143a180>] ? __driver_attach+0xb0/0xb0
[ 375.261494] [<ffffffff8143a1d3>] __device_attach+0x53/0x60
[ 375.328206] [<ffffffff81437dac>] bus_for_each_drv+0x6c/0xa0
[ 375.395950] [<ffffffff81439cf8>] device_attach+0xa8/0xc0
[ 375.460578] [<ffffffff814389d0>] bus_probe_device+0xb0/0xe0
[ 375.528318] [<ffffffff81437421>] device_add+0x301/0x570
[ 375.591883] [<ffffffff814376ae>] device_register+0x1e/0x30
[ 375.658568] [<ffffffff813a56bf>] acpi_device_register+0x1af/0x2bf
[ 375.732590] [<ffffffff813a59ae>] acpi_add_single_object+0x1df/0x2b9
[ 375.808640] [<ffffffff813ce320>] ? acpi_ut_release_mutex+0xac/0xb5
[ 375.883646] [<ffffffff813a5b93>] acpi_bus_check_add+0x10b/0x166
[ 375.955529] [<ffffffff810db4ad>] ? trace_hardirqs_on+0xd/0x10
[ 376.025327] [<ffffffff8109fa4f>] ? up+0x2f/0x50
[ 376.080639] [<ffffffff813a0cc1>] ? acpi_os_signal_semaphore+0x6b/0x74
[ 376.158792] [<ffffffff813c3f1d>] acpi_ns_walk_namespace+0xbe/0x17d
[ 376.233854] [<ffffffff813a5a88>] ? acpi_add_single_object+0x2b9/0x2b9
[ 376.312012] [<ffffffff813a5a88>] ? acpi_add_single_object+0x2b9/0x2b9
[ 376.390162] [<ffffffff813c43b3>] acpi_walk_namespace+0x8a/0xc4
[ 376.461051] [<ffffffff813a5c49>] acpi_bus_scan+0x5b/0x7c
[ 376.525707] [<ffffffff813a5cd6>] acpi_bus_add+0x2a/0x2c
[ 376.589344] [<ffffffff813d5dc6>] container_notify_cb+0x103/0x18d
[ 376.662309] [<ffffffff813b3946>] acpi_ev_notify_dispatch+0x41/0x5f
[ 376.737386] [<ffffffff813a0f47>] acpi_os_execute_deferred+0x27/0x34
[ 376.813507] [<ffffffff81090279>] process_one_work+0x219/0x680
[ 376.883357] [<ffffffff81090218>] ? process_one_work+0x1b8/0x680
[ 376.955312] [<ffffffff813a0f20>] ? acpi_os_wait_events_complete+0x23/0x23
[ 377.037615] [<ffffffff8109212e>] worker_thread+0x12e/0x320
[ 377.104365] [<ffffffff81092000>] ? manage_workers+0x190/0x190
[ 377.174274] [<ffffffff81098106>] kthread+0xc6/0xd0
[ 377.232697] [<ffffffff81678b04>] kernel_thread_helper+0x4/0x10
[ 377.303588] [<ffffffff8166e570>] ? retint_restore_args+0x13/0x13
[ 377.376550] [<ffffffff81098040>] ? __init_kthread_worker+0x70/0x70
[ 377.451591] [<ffffffff81678b00>] ? gs_change+0x13/0x13
[ 377.514247] ------------[ cut here ]------------
[ 377.569481] WARNING: at lib/kobject.c:166 kobject_add_internal+0x1b3/0x260()
[ 377.653796] Hardware name: PRIMEQUEST 1800E
[ 377.703865] kobject: (ffffffff82c15718): attempted to be registered with empty name!
[ 377.796584] Modules linked in: bridge stp llc sunrpc ipt_REJECT nf_conntrack_ipv4 nf_defrag_ipv4 iptable_filter ip_tables ip6t_REJECT nf_conntrack_ipv6 nf_defrag_ipv6 xt_state nf_conntrack ip6table_filter ip6_tables binfmt_misc vfat fat dm_mirror dm_region_hash dm_log dm_mod uinput iTCO_wdt iTCO_vendor_support coretemp kvm_intel kvm crc32c_intel microcode pcspkr lpc_ich mfd_core i2c_i801 i2c_core ioatdma i7core_edac edac_core sg acpi_memhotplug e1000e igb dca sd_mod crc_t10dif lpfc scsi_transport_fc scsi_tgt mptsas mptscsih mptbase scsi_transport_sas scsi_mod
[ 378.400511] Pid: 4, comm: kworker/0:0 Tainted: G W 3.6.0 #5
[ 378.477614] Call Trace:
[ 378.506916] [<ffffffff8106c10f>] warn_slowpath_common+0x7f/0xc0
[ 378.578843] [<ffffffff8106c206>] warn_slowpath_fmt+0x46/0x50
[ 378.647658] [<ffffffff810db09d>] ? mark_held_locks+0x8d/0x140
[ 378.717504] [<ffffffff8133cda3>] kobject_add_internal+0x1b3/0x260
[ 378.791507] [<ffffffff8133cff8>] kobject_add_varg+0x38/0x60
[ 378.859187] [<ffffffff8133d0d4>] kobject_add+0x44/0x70
[ 378.921769] [<ffffffff81098d76>] ? __init_waitqueue_head+0x46/0x60
[ 378.996747] [<ffffffff814371f4>] device_add+0xd4/0x570
[ 379.059342] [<ffffffff814376ae>] device_register+0x1e/0x30
[ 379.126042] [<ffffffff81449b15>] register_node+0x25/0xe0
[ 379.190652] [<ffffffff8144a057>] register_one_node+0x67/0x140
[ 379.260532] [<ffffffff81652e40>] add_memory+0x100/0x1f0
[ 379.324175] [<ffffffffa00a31c6>] acpi_memory_enable_device+0x92/0xdf [acpi_memhotplug]
[ 379.419903] [<ffffffffa00a3753>] acpi_memory_device_add+0x10d/0x116 [acpi_memhotplug]
[ 379.514628] [<ffffffff813a4376>] acpi_device_probe+0x50/0x18a
[ 379.584489] [<ffffffff8124b053>] ? sysfs_create_link+0x13/0x20
[ 379.655351] [<ffffffff81439d7c>] really_probe+0x6c/0x320
[ 379.720047] [<ffffffff8143a077>] driver_probe_device+0x47/0xa0
[ 379.790863] [<ffffffff8143a180>] ? __driver_attach+0xb0/0xb0
[ 379.859667] [<ffffffff8143a180>] ? __driver_attach+0xb0/0xb0
[ 379.928526] [<ffffffff8143a1d3>] __device_attach+0x53/0x60
[ 379.995218] [<ffffffff81437dac>] bus_for_each_drv+0x6c/0xa0
[ 380.063010] [<ffffffff81439cf8>] device_attach+0xa8/0xc0
[ 380.127664] [<ffffffff814389d0>] bus_probe_device+0xb0/0xe0
[ 380.195449] [<ffffffff81437421>] device_add+0x301/0x570
[ 380.259081] [<ffffffff814376ae>] device_register+0x1e/0x30
[ 380.325840] [<ffffffff813a56bf>] acpi_device_register+0x1af/0x2bf
[ 380.399852] [<ffffffff813a59ae>] acpi_add_single_object+0x1df/0x2b9
[ 380.475874] [<ffffffff813ce320>] ? acpi_ut_release_mutex+0xac/0xb5
[ 380.550884] [<ffffffff813a5b93>] acpi_bus_check_add+0x10b/0x166
[ 380.622761] [<ffffffff810db4ad>] ? trace_hardirqs_on+0xd/0x10
[ 380.692529] [<ffffffff8109fa4f>] ? up+0x2f/0x50
[ 380.747792] [<ffffffff813a0cc1>] ? acpi_os_signal_semaphore+0x6b/0x74
[ 380.825974] [<ffffffff813c3f1d>] acpi_ns_walk_namespace+0xbe/0x17d
[ 380.901027] [<ffffffff813a5a88>] ? acpi_add_single_object+0x2b9/0x2b9
[ 380.979208] [<ffffffff813a5a88>] ? acpi_add_single_object+0x2b9/0x2b9
[ 381.057328] [<ffffffff813c43b3>] acpi_walk_namespace+0x8a/0xc4
[ 381.128253] [<ffffffff813a5c49>] acpi_bus_scan+0x5b/0x7c
[ 381.192922] [<ffffffff813a5cd6>] acpi_bus_add+0x2a/0x2c
[ 381.256577] [<ffffffff813d5dc6>] container_notify_cb+0x103/0x18d
[ 381.329551] [<ffffffff813b3946>] acpi_ev_notify_dispatch+0x41/0x5f
[ 381.404612] [<ffffffff813a0f47>] acpi_os_execute_deferred+0x27/0x34
[ 381.480709] [<ffffffff81090279>] process_one_work+0x219/0x680
[ 381.550600] [<ffffffff81090218>] ? process_one_work+0x1b8/0x680
[ 381.622535] [<ffffffff813a0f20>] ? acpi_os_wait_events_complete+0x23/0x23
[ 381.704882] [<ffffffff8109212e>] worker_thread+0x12e/0x320
[ 381.771655] [<ffffffff81092000>] ? manage_workers+0x190/0x190
[ 381.841554] [<ffffffff81098106>] kthread+0xc6/0xd0
[ 381.899995] [<ffffffff81678b04>] kernel_thread_helper+0x4/0x10
[ 381.970815] [<ffffffff8166e570>] ? retint_restore_args+0x13/0x13
[ 382.043793] [<ffffffff81098040>] ? __init_kthread_worker+0x70/0x70
[ 382.118880] [<ffffffff81678b00>] ? gs_change+0x13/0x13
[ 382.181437] ---[ end trace a3ee526778d7b765 ]---
Thanks,
Yasuaki Ishimatsu
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