![Eric W. Biederman](/assets/img/avatar_default.png)
Holding locks over device_del -> kobject_del -> sysfs_deactivate can cause deadlocks if those same locks are grabbed in sysfs show or store methods. The I model s_active count + completion as a sleeping read/write lock. I describe to lockdep sysfs_get_active as a read_trylock, sysfs_put_active as a read_unlock, and sysfs_deactivate as a write_lock and write_unlock pair. This seems to capture the essence for purposes of finding deadlocks, and in my testing gives finds real issues and ignores non-issues. This brings us back to holding locks over kobject_del is a problem that ideally we should find a way of addressing, but at least lockdep can tell us about the problems instead of requiring developers to debug rare strange system deadlocks, that happen when sysfs files are removed while being written to. Signed-off-by: Eric W. Biederman <ebiederm@xmission.com> Acked-by: Tejun Heo <tj@kernel.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
202 lines
5.4 KiB
C
202 lines
5.4 KiB
C
/*
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* fs/sysfs/sysfs.h - sysfs internal header file
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*
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* Copyright (c) 2001-3 Patrick Mochel
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* Copyright (c) 2007 SUSE Linux Products GmbH
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* Copyright (c) 2007 Tejun Heo <teheo@suse.de>
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*
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* This file is released under the GPLv2.
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*/
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#include <linux/lockdep.h>
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#include <linux/fs.h>
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struct sysfs_open_dirent;
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/* type-specific structures for sysfs_dirent->s_* union members */
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struct sysfs_elem_dir {
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struct kobject *kobj;
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/* children list starts here and goes through sd->s_sibling */
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struct sysfs_dirent *children;
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};
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struct sysfs_elem_symlink {
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struct sysfs_dirent *target_sd;
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};
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struct sysfs_elem_attr {
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struct attribute *attr;
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struct sysfs_open_dirent *open;
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};
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struct sysfs_elem_bin_attr {
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struct bin_attribute *bin_attr;
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struct hlist_head buffers;
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};
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struct sysfs_inode_attrs {
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struct iattr ia_iattr;
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void *ia_secdata;
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u32 ia_secdata_len;
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};
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/*
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* sysfs_dirent - the building block of sysfs hierarchy. Each and
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* every sysfs node is represented by single sysfs_dirent.
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*
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* As long as s_count reference is held, the sysfs_dirent itself is
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* accessible. Dereferencing s_elem or any other outer entity
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* requires s_active reference.
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*/
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struct sysfs_dirent {
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atomic_t s_count;
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atomic_t s_active;
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#ifdef CONFIG_DEBUG_LOCK_ALLOC
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struct lockdep_map dep_map;
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#endif
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struct sysfs_dirent *s_parent;
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struct sysfs_dirent *s_sibling;
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const char *s_name;
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union {
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struct sysfs_elem_dir s_dir;
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struct sysfs_elem_symlink s_symlink;
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struct sysfs_elem_attr s_attr;
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struct sysfs_elem_bin_attr s_bin_attr;
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};
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unsigned int s_flags;
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ino_t s_ino;
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umode_t s_mode;
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struct sysfs_inode_attrs *s_iattr;
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};
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#define SD_DEACTIVATED_BIAS INT_MIN
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#define SYSFS_TYPE_MASK 0x00ff
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#define SYSFS_DIR 0x0001
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#define SYSFS_KOBJ_ATTR 0x0002
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#define SYSFS_KOBJ_BIN_ATTR 0x0004
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#define SYSFS_KOBJ_LINK 0x0008
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#define SYSFS_COPY_NAME (SYSFS_DIR | SYSFS_KOBJ_LINK)
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#define SYSFS_FLAG_MASK ~SYSFS_TYPE_MASK
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#define SYSFS_FLAG_REMOVED 0x0200
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static inline unsigned int sysfs_type(struct sysfs_dirent *sd)
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{
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return sd->s_flags & SYSFS_TYPE_MASK;
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}
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#ifdef CONFIG_DEBUG_LOCK_ALLOC
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#define sysfs_dirent_init_lockdep(sd) \
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do { \
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static struct lock_class_key __key; \
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\
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lockdep_init_map(&sd->dep_map, "s_active", &__key, 0); \
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} while(0)
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#else
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#define sysfs_dirent_init_lockdep(sd) do {} while(0)
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#endif
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/*
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* Context structure to be used while adding/removing nodes.
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*/
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struct sysfs_addrm_cxt {
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struct sysfs_dirent *parent_sd;
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struct sysfs_dirent *removed;
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};
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/*
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* mount.c
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*/
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extern struct sysfs_dirent sysfs_root;
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extern struct super_block *sysfs_sb;
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extern struct kmem_cache *sysfs_dir_cachep;
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/*
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* dir.c
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*/
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extern struct mutex sysfs_mutex;
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extern spinlock_t sysfs_assoc_lock;
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extern const struct file_operations sysfs_dir_operations;
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extern const struct inode_operations sysfs_dir_inode_operations;
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struct dentry *sysfs_get_dentry(struct sysfs_dirent *sd);
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struct sysfs_dirent *sysfs_get_active_two(struct sysfs_dirent *sd);
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void sysfs_put_active_two(struct sysfs_dirent *sd);
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void sysfs_addrm_start(struct sysfs_addrm_cxt *acxt,
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struct sysfs_dirent *parent_sd);
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int __sysfs_add_one(struct sysfs_addrm_cxt *acxt, struct sysfs_dirent *sd);
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int sysfs_add_one(struct sysfs_addrm_cxt *acxt, struct sysfs_dirent *sd);
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void sysfs_remove_one(struct sysfs_addrm_cxt *acxt, struct sysfs_dirent *sd);
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void sysfs_addrm_finish(struct sysfs_addrm_cxt *acxt);
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struct sysfs_dirent *sysfs_find_dirent(struct sysfs_dirent *parent_sd,
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const unsigned char *name);
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struct sysfs_dirent *sysfs_get_dirent(struct sysfs_dirent *parent_sd,
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const unsigned char *name);
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struct sysfs_dirent *sysfs_new_dirent(const char *name, umode_t mode, int type);
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void release_sysfs_dirent(struct sysfs_dirent *sd);
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int sysfs_create_subdir(struct kobject *kobj, const char *name,
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struct sysfs_dirent **p_sd);
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void sysfs_remove_subdir(struct sysfs_dirent *sd);
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int sysfs_rename(struct sysfs_dirent *sd,
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struct sysfs_dirent *new_parent_sd, const char *new_name);
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static inline struct sysfs_dirent *__sysfs_get(struct sysfs_dirent *sd)
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{
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if (sd) {
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WARN_ON(!atomic_read(&sd->s_count));
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atomic_inc(&sd->s_count);
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}
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return sd;
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}
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#define sysfs_get(sd) __sysfs_get(sd)
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static inline void __sysfs_put(struct sysfs_dirent *sd)
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{
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if (sd && atomic_dec_and_test(&sd->s_count))
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release_sysfs_dirent(sd);
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}
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#define sysfs_put(sd) __sysfs_put(sd)
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/*
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* inode.c
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*/
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struct inode *sysfs_get_inode(struct sysfs_dirent *sd);
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void sysfs_delete_inode(struct inode *inode);
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int sysfs_sd_setattr(struct sysfs_dirent *sd, struct iattr *iattr);
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int sysfs_permission(struct inode *inode, int mask);
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int sysfs_setattr(struct dentry *dentry, struct iattr *iattr);
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int sysfs_getattr(struct vfsmount *mnt, struct dentry *dentry, struct kstat *stat);
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int sysfs_setxattr(struct dentry *dentry, const char *name, const void *value,
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size_t size, int flags);
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int sysfs_hash_and_remove(struct sysfs_dirent *dir_sd, const char *name);
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int sysfs_inode_init(void);
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/*
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* file.c
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*/
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extern const struct file_operations sysfs_file_operations;
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int sysfs_add_file(struct sysfs_dirent *dir_sd,
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const struct attribute *attr, int type);
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int sysfs_add_file_mode(struct sysfs_dirent *dir_sd,
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const struct attribute *attr, int type, mode_t amode);
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/*
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* bin.c
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*/
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extern const struct file_operations bin_fops;
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void unmap_bin_file(struct sysfs_dirent *attr_sd);
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/*
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* symlink.c
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*/
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extern const struct inode_operations sysfs_symlink_inode_operations;
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