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Date: Fri, 5 Oct 2012 10:00:43 +0900 From: Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com> To: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com> CC: <wency@...fujitsu.com>, <linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>, <rientjes@...gle.com>, <liuj97@...il.com>, <len.brown@...el.com>, <benh@...nel.crashing.org>, <paulus@...ba.org>, <minchan.kim@...il.com>, <akpm@...ux-foundation.org> Subject: Re: [PATCH 2/4] memory-hotplug: add node_device_release Hi Kosaki-san, 2012/10/02 3:12, KOSAKI Motohiro wrote: > On Mon, Oct 1, 2012 at 2:54 AM, Yasuaki Ishimatsu > <isimatu.yasuaki@...fujitsu.com> 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 > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@...r.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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