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authorTejun Heo <htejun@gmail.com>2007-09-20 16:05:12 +0900
committerGreg Kroah-Hartman <gregkh@suse.de>2007-10-12 14:51:11 -0700
commita4e8b912541d5372ae049a3b7c1979968e52c40b (patch)
treea95937748b6216f914abe55ed47c2627e7856bf7 /fs/sysfs/file.c
parent85a4ffad3de77177591f7c2c18c26c3c8dd28bff (diff)
downloadvexpress-lsk-a4e8b912541d5372ae049a3b7c1979968e52c40b.tar.gz
sysfs: move sysfs file poll implementation to sysfs_open_dirent
Sysfs file poll implementation is scattered over sysfs and kobject. Event numbering is done in sysfs_dirent but wait itself is done on kobject. This not only unecessarily bloats both kobject and sysfs_dirent but is also buggy - if a sysfs_dirent is removed while there still are pollers, the associaton betwen the kobject and sysfs_dirent breaks and kobject may be freed with the pollers still sleeping on it. This patch moves whole poll implementation into sysfs_open_dirent. Each time a sysfs_open_dirent is created, event number restarts from 1 and pollers sleep on sysfs_open_dirent. As event sequence number is meaningless without any open file and pollers should have open file and thus sysfs_open_dirent, this ephemeral event counting works and is a saner implementation. This patch fixes the dnagling sleepers bug and reduces the sizes of kobject and sysfs_dirent by one pointer. Signed-off-by: Tejun Heo <htejun@gmail.com> Acked-by: Cornelia Huck <cornelia.huck@de.ibm.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Diffstat (limited to 'fs/sysfs/file.c')
-rw-r--r--fs/sysfs/file.c25
1 files changed, 19 insertions, 6 deletions
diff --git a/fs/sysfs/file.c b/fs/sysfs/file.c
index b13ba94cf8a..c05f9618b2d 100644
--- a/fs/sysfs/file.c
+++ b/fs/sysfs/file.c
@@ -62,6 +62,8 @@ static spinlock_t sysfs_open_dirent_lock = SPIN_LOCK_UNLOCKED;
struct sysfs_open_dirent {
atomic_t refcnt;
+ atomic_t event;
+ wait_queue_head_t poll;
struct list_head buffers; /* goes through sysfs_buffer.list */
};
@@ -104,7 +106,7 @@ static int fill_read_buffer(struct dentry * dentry, struct sysfs_buffer * buffer
if (!sysfs_get_active_two(attr_sd))
return -ENODEV;
- buffer->event = atomic_read(&attr_sd->s_event);
+ buffer->event = atomic_read(&attr_sd->s_attr.open->event);
count = ops->show(kobj, attr_sd->s_attr.attr, buffer->page);
sysfs_put_active_two(attr_sd);
@@ -301,6 +303,8 @@ static int sysfs_get_open_dirent(struct sysfs_dirent *sd,
return -ENOMEM;
atomic_set(&new_od->refcnt, 0);
+ atomic_set(&new_od->event, 1);
+ init_waitqueue_head(&new_od->poll);
INIT_LIST_HEAD(&new_od->buffers);
goto retry;
}
@@ -443,17 +447,17 @@ static unsigned int sysfs_poll(struct file *filp, poll_table *wait)
{
struct sysfs_buffer * buffer = filp->private_data;
struct sysfs_dirent *attr_sd = filp->f_path.dentry->d_fsdata;
- struct kobject *kobj = attr_sd->s_parent->s_dir.kobj;
+ struct sysfs_open_dirent *od = attr_sd->s_attr.open;
/* need parent for the kobj, grab both */
if (!sysfs_get_active_two(attr_sd))
goto trigger;
- poll_wait(filp, &kobj->poll, wait);
+ poll_wait(filp, &od->poll, wait);
sysfs_put_active_two(attr_sd);
- if (buffer->event != atomic_read(&attr_sd->s_event))
+ if (buffer->event != atomic_read(&od->event))
goto trigger;
return 0;
@@ -474,8 +478,17 @@ void sysfs_notify(struct kobject *k, char *dir, char *attr)
if (sd && attr)
sd = sysfs_find_dirent(sd, attr);
if (sd) {
- atomic_inc(&sd->s_event);
- wake_up_interruptible(&k->poll);
+ struct sysfs_open_dirent *od;
+
+ spin_lock(&sysfs_open_dirent_lock);
+
+ od = sd->s_attr.open;
+ if (od) {
+ atomic_inc(&od->event);
+ wake_up_interruptible(&od->poll);
+ }
+
+ spin_unlock(&sysfs_open_dirent_lock);
}
mutex_unlock(&sysfs_mutex);