On Tue, Apr 16, 2019 at 06:53:35PM +0300, Konstantin Khorenko wrote: > __kernfs_remove() which is called under kernfs_mutex, > assumes nobody kills kernfs node whie it's working on it > and "get"s current kernfs node for that. > > But we hit a warning in kernfs_get(): kn->counter == 0 already: > ------------[ cut here ]------------ > WARNING: CPU: 2 PID: 63923 at fs/kernfs/dir.c:377 kernfs_get+0x2f/0x40 > ... > Call Trace: > [<ffffffffa7f92e67>] dump_stack+0x19/0x1b > [<ffffffffa78987b8>] __warn+0xd8/0x100 > [<ffffffffa78988fd>] warn_slowpath_null+0x1d/0x20 > [<ffffffffa7aecaff>] kernfs_get+0x2f/0x40 > [<ffffffffa7aed233>] __kernfs_remove+0x113/0x260 > [<ffffffffa7aee201>] kernfs_remove+0x21/0x30 > [<ffffffffa7af1010>] sysfs_remove_dir+0x50/0x80 > [<ffffffffa7b9fb38>] kobject_del+0x18/0x50 > [<ffffffffa7a38a4d>] sysfs_slab_remove+0x3d/0x50 > [<ffffffffa79f1e6b>] do_kmem_cache_release+0x3b/0x70 > [<ffffffffa79f2aa1>] memcg_destroy_kmem_caches+0xb1/0xf0 > [<ffffffffa7a4ed5c>] mem_cgroup_css_free+0x4c/0x280 > [<ffffffffa79377fc>] cgroup_free_fn+0x4c/0x120 > [<ffffffffa78bc222>] process_one_work+0x182/0x440 > [<ffffffffa78bd3d6>] worker_thread+0x126/0x3c0 > [<ffffffffa78c4441>] kthread+0xd1/0xe0 > > This could be for example because of kernfs_notify_workfn() which > does kernfs_put(kn) out of kernfs_mutex held section, > so move kernfs_put(kn) under the mutex.
This patch doesn't really make sense to me. Can you give a more concrete scenario where this would help? Thanks. -- tejun
