提交 a4e8b912 编写于 作者: T Tejun Heo 提交者: Greg Kroah-Hartman

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: NTejun Heo <htejun@gmail.com>
Acked-by: NCornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>
上级 85a4ffad
......@@ -318,7 +318,6 @@ struct sysfs_dirent *sysfs_new_dirent(const char *name, umode_t mode, int type)
atomic_set(&sd->s_count, 1);
atomic_set(&sd->s_active, 0);
atomic_set(&sd->s_event, 1);
sd->s_name = name;
sd->s_mode = mode;
......
......@@ -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);
......
......@@ -46,7 +46,6 @@ struct sysfs_dirent {
ino_t s_ino;
umode_t s_mode;
struct iattr *s_iattr;
atomic_t s_event;
};
#define SD_DEACTIVATED_BIAS INT_MIN
......
......@@ -66,7 +66,6 @@ struct kobject {
struct kset * kset;
struct kobj_type * ktype;
struct sysfs_dirent * sd;
wait_queue_head_t poll;
};
extern int kobject_set_name(struct kobject *, const char *, ...)
......
......@@ -131,7 +131,6 @@ void kobject_init(struct kobject * kobj)
return;
kref_init(&kobj->kref);
INIT_LIST_HEAD(&kobj->entry);
init_waitqueue_head(&kobj->poll);
kobj->kset = kset_get(kobj->kset);
}
......
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