ping ... On 2014/10/9 20:47, Weng Meiling wrote: > On 2014/10/9 20:43, Weng Meiling wrote: >> Hi guys, >> >> I see the mails you discussed the BUG at fs/sysfs/group.c:65! triggered by >> duplicated sysfs link. >> >> the detail mail: >> >> https://lkml.org/lkml/2013/3/8/370 >> >> but it seems the problems has no conclusion. In our environment, we >> triggered the bug too, but for error ENOENT: >> >> we use 3.4 kernel, and do virtual disk device create / remove for many >> times. Before remove we can see the devices: >> >> #ll /sys/devices/virtual/block/ >> drwxr-xr-x 7 root root 0 Oct 6 09:17 sd-1a >> drwxr-xr-x 7 root root 0 Oct 6 09:17 sd-2a >> >> when the two virtual devices were removed, the directory block/ was delete >> too. >> >> after many times create / remove, the kernel trigger the bug (just the main >> call trace): >> >> [ 3965.441713] WARNING: at >> /usr/src/packages/BUILD/linux-3.4/lib/kobject.c:202 >> kobject_add_internal+0x11f/0x280() >> [ 3965.441716] Hardware name: Romley >> [ 3965.441718] kobject_add_internal failed for sd-1a (error: -2 parent: >> block) >> >> [ 3965.441817] Call Trace: >> [ 3965.441820] [<ffffffff8103717a>] warn_slowpath_common+0x7a/0xb0 >> [ 3965.441823] [<ffffffff81037251>] warn_slowpath_fmt+0x41/0x50 >> [ 3965.441826] [<ffffffff81215e0f>] kobject_add_internal+0x11f/0x280 >> [ 3965.441830] [<ffffffff81216267>] kobject_add+0x67/0xc0 >> [ 3965.441833] [<ffffffff812d2305>] device_add+0x105/0x6d0 >> [ 3965.441836] [<ffffffff812d0dbc>] ? dev_set_name+0x3c/0x40 >> [ 3965.441839] [<ffffffff812030ac>] add_disk+0x1bc/0x490 >> >> [ 3965.441912] kernel BUG at >> /usr/src/packages/BUILD/linux-3.4/fs/sysfs/group.c:65! >> [ 3965.441915] invalid opcode: 0000 [#1] SMP >> [ 3965.686738] Call Trace: >> [ 3965.686743] [<ffffffff811a677e>] sysfs_create_group+0xe/0x10 >> [ 3965.686748] [<ffffffff810cfb04>] blk_trace_init_sysfs+0x14/0x20 >> [ 3965.686753] [<ffffffff811fcabb>] blk_register_queue+0x3b/0x120 >> [ 3965.686756] [<ffffffff812030bc>] add_disk+0x1cc/0x490 >> >> from the error "kobject_add_internal failed for sd-1a (error: -2 parent: >> block)", we found that the first >> warning was caused by the disk device's parent_sd was null when it was added >> into sysfs: >> >> int sysfs_create_dir(struct kobject * kobj) >> { >> ... >> if (kobj->parent) >> parent_sd = kobj->parent->sd; >> else >> parent_sd = &sysfs_root; >> >> if (!parent_sd) >> return -ENOENT; >> ... >> } >> >> The virtual disk device was not added into sysfs because of the above >> failure, and the kobj->sd was >> not set, then trigger the bug when creating attribute group under the >> device's directory: >> >> static int internal_create_group(struct kobject *kobj, int update, >> const struct attribute_group *grp) >> { >> ... >> BUG_ON(!kobj || (!update && !kobj->sd)); >> ... >> } >> >> Walk the code, it seems there maybe a race between block/ remove and virtual >> disk devices' register: >> >> when the two virtual devices were removed, the block/ directory's refcount >> became 0, will into: >> >> path0(remove the block/) >> path1(register virtual device sd-1a) >> >> kobject_del(){ >> get_device_parent(){ >> ... ... >> sysfs_remove_dir(kobj); //kobj->sd=0 >> spin_lock(&dev->class->p->glue_dirs.list_lock); > > this should be kobj->sd = NULL >> ... <========= >> list_for_each_entry(k, &dev->class->p->glue_dirs.list, entry) //get parent >> kobject from kset list >> kobj_kset_leave(kobj); //remove kobj from kset list ... >> } } >> >> If getting parent object between " kobj->sd=0 " and >> "remove_kset_leave(kobj)", the sysfs_create_dir() will return ENOENT and >> trigger the BUG later. >> > this should be kobj->sd = NULL > >> The lastest kernel seems to be the same. But I am not familiar with block >> device, I am not sure whether the analysis is right or I am missing >> something. >> what do you think about this situation? Any suggestion is appreciative. >> Thanks! >> >> > >
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