diff options
| -rw-r--r-- | fs/sysfs/dir.c | 74 | ||||
| -rw-r--r-- | fs/sysfs/sysfs.h | 13 |
2 files changed, 50 insertions, 37 deletions
diff --git a/fs/sysfs/dir.c b/fs/sysfs/dir.c index f5f0b936f181..40596a0eee52 100644 --- a/fs/sysfs/dir.c +++ b/fs/sysfs/dir.c @@ -10,6 +10,7 @@ #include <linux/kobject.h> #include <linux/namei.h> #include <linux/idr.h> +#include <linux/completion.h> #include <asm/semaphore.h> #include "sysfs.h" @@ -32,11 +33,24 @@ static DEFINE_IDA(sysfs_ino_ida); */ struct sysfs_dirent *sysfs_get_active(struct sysfs_dirent *sd) { - if (sd) { - if (unlikely(!down_read_trylock(&sd->s_active))) - sd = NULL; + if (unlikely(!sd)) + return NULL; + + while (1) { + int v, t; + + v = atomic_read(&sd->s_active); + if (unlikely(v < 0)) + return NULL; + + t = atomic_cmpxchg(&sd->s_active, v, v + 1); + if (likely(t == v)) + return sd; + if (t < 0) + return NULL; + + cpu_relax(); } - return sd; } /** @@ -48,8 +62,21 @@ struct sysfs_dirent *sysfs_get_active(struct sysfs_dirent *sd) */ void sysfs_put_active(struct sysfs_dirent *sd) { - if (sd) - up_read(&sd->s_active); + struct completion *cmpl; + int v; + + if (unlikely(!sd)) + return; + + v = atomic_dec_return(&sd->s_active); + if (likely(v != SD_DEACTIVATED_BIAS)) + return; + + /* atomic_dec_return() is a mb(), we'll always see the updated + * sd->s_sibling.next. + */ + cmpl = (void *)sd->s_sibling.next; + complete(cmpl); } /** @@ -95,17 +122,25 @@ void sysfs_put_active_two(struct sysfs_dirent *sd) * sysfs_deactivate - deactivate sysfs_dirent * @sd: sysfs_dirent to deactivate * - * Deny new active references and drain existing ones. s_active - * will be unlocked when the sysfs_dirent is released. + * Deny new active references and drain existing ones. */ void sysfs_deactivate(struct sysfs_dirent *sd) { - down_write_nested(&sd->s_active, SYSFS_S_ACTIVE_DEACTIVATE); + DECLARE_COMPLETION_ONSTACK(wait); + int v; + + BUG_ON(!list_empty(&sd->s_sibling)); + sd->s_sibling.next = (void *)&wait; - /* s_active will be unlocked by the thread doing the final put - * on @sd. Lie to lockdep. + /* atomic_add_return() is a mb(), put_active() will always see + * the updated sd->s_sibling.next. */ - rwsem_release(&sd->s_active.dep_map, 1, _RET_IP_); + v = atomic_add_return(SD_DEACTIVATED_BIAS, &sd->s_active); + + if (v != SD_DEACTIVATED_BIAS) + wait_for_completion(&wait); + + INIT_LIST_HEAD(&sd->s_sibling); } static int sysfs_alloc_ino(ino_t *pino) @@ -141,19 +176,6 @@ void release_sysfs_dirent(struct sysfs_dirent * sd) repeat: parent_sd = sd->s_parent; - /* If @sd is being released after deletion, s_active is write - * locked. If @sd is cursor for directory walk or being - * released prematurely, s_active has no reader or writer. - * - * sysfs_deactivate() lies to lockdep that s_active is - * unlocked immediately. Lie one more time to cover the - * previous lie. - */ - if (!down_write_trylock(&sd->s_active)) - rwsem_acquire(&sd->s_active.dep_map, - SYSFS_S_ACTIVE_DEACTIVATE, 0, _RET_IP_); - up_write(&sd->s_active); - if (sd->s_type & SYSFS_KOBJ_LINK) sysfs_put(sd->s_elem.symlink.target_sd); if (sd->s_type & SYSFS_COPY_NAME) @@ -213,8 +235,8 @@ struct sysfs_dirent *sysfs_new_dirent(const char *name, umode_t mode, int type) goto err_out; atomic_set(&sd->s_count, 1); + atomic_set(&sd->s_active, 0); atomic_set(&sd->s_event, 1); - init_rwsem(&sd->s_active); INIT_LIST_HEAD(&sd->s_children); INIT_LIST_HEAD(&sd->s_sibling); diff --git a/fs/sysfs/sysfs.h b/fs/sysfs/sysfs.h index f8779eaa53ff..ae006b070bf0 100644 --- a/fs/sysfs/sysfs.h +++ b/fs/sysfs/sysfs.h @@ -21,7 +21,7 @@ struct sysfs_elem_bin_attr { */ struct sysfs_dirent { atomic_t s_count; - struct rw_semaphore s_active; + atomic_t s_active; struct sysfs_dirent * s_parent; struct list_head s_sibling; struct list_head s_children; @@ -42,16 +42,7 @@ struct sysfs_dirent { atomic_t s_event; }; -/* - * A sysfs file which deletes another file when written to need to - * write lock the s_active of the victim while its s_active is read - * locked for the write operation. Tell lockdep that this is okay. - */ -enum sysfs_s_active_class -{ - SYSFS_S_ACTIVE_NORMAL, /* file r/w access, etc - default */ - SYSFS_S_ACTIVE_DEACTIVATE, /* file deactivation */ -}; +#define SD_DEACTIVATED_BIAS INT_MIN extern struct vfsmount * sysfs_mount; extern struct kmem_cache *sysfs_dir_cachep; |