Revision 2cc78eb52bc1ae89f0a4fa5a00eb998dffde4a9f authored by Linus Torvalds on 17 October 2005, 16:10:15 UTC, committed by Linus Torvalds on 17 October 2005, 16:10:15 UTC
Dipankar made RCU limit the batch size to improve latency, but that approach is unworkable: it can cause the RCU queues to grow without bounds, since the batch limiter ended up limiting the callbacks. So make the limit much higher, and start planning on instead limiting the batch size by doing RCU callbacks more often if the queue looks like it might be growing too long. Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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char_dev.c
/*
* linux/fs/char_dev.c
*
* Copyright (C) 1991, 1992 Linus Torvalds
*/
#include <linux/config.h>
#include <linux/init.h>
#include <linux/fs.h>
#include <linux/slab.h>
#include <linux/string.h>
#include <linux/major.h>
#include <linux/errno.h>
#include <linux/module.h>
#include <linux/smp_lock.h>
#include <linux/devfs_fs_kernel.h>
#include <linux/kobject.h>
#include <linux/kobj_map.h>
#include <linux/cdev.h>
#ifdef CONFIG_KMOD
#include <linux/kmod.h>
#endif
static struct kobj_map *cdev_map;
#define MAX_PROBE_HASH 255 /* random */
static DECLARE_MUTEX(chrdevs_lock);
static struct char_device_struct {
struct char_device_struct *next;
unsigned int major;
unsigned int baseminor;
int minorct;
const char *name;
struct file_operations *fops;
struct cdev *cdev; /* will die */
} *chrdevs[MAX_PROBE_HASH];
/* index in the above */
static inline int major_to_index(int major)
{
return major % MAX_PROBE_HASH;
}
/* get char device names in somewhat random order */
int get_chrdev_list(char *page)
{
struct char_device_struct *cd;
int i, len;
len = sprintf(page, "Character devices:\n");
down(&chrdevs_lock);
for (i = 0; i < ARRAY_SIZE(chrdevs) ; i++) {
for (cd = chrdevs[i]; cd; cd = cd->next) {
/*
* if the current name, plus the 5 extra characters
* in the device line for this entry
* would run us off the page, we're done
*/
if ((len+strlen(cd->name) + 5) >= PAGE_SIZE)
goto page_full;
len += sprintf(page+len, "%3d %s\n",
cd->major, cd->name);
}
}
page_full:
up(&chrdevs_lock);
return len;
}
/*
* Register a single major with a specified minor range.
*
* If major == 0 this functions will dynamically allocate a major and return
* its number.
*
* If major > 0 this function will attempt to reserve the passed range of
* minors and will return zero on success.
*
* Returns a -ve errno on failure.
*/
static struct char_device_struct *
__register_chrdev_region(unsigned int major, unsigned int baseminor,
int minorct, const char *name)
{
struct char_device_struct *cd, **cp;
int ret = 0;
int i;
cd = kmalloc(sizeof(struct char_device_struct), GFP_KERNEL);
if (cd == NULL)
return ERR_PTR(-ENOMEM);
memset(cd, 0, sizeof(struct char_device_struct));
down(&chrdevs_lock);
/* temporary */
if (major == 0) {
for (i = ARRAY_SIZE(chrdevs)-1; i > 0; i--) {
if (chrdevs[i] == NULL)
break;
}
if (i == 0) {
ret = -EBUSY;
goto out;
}
major = i;
ret = major;
}
cd->major = major;
cd->baseminor = baseminor;
cd->minorct = minorct;
cd->name = name;
i = major_to_index(major);
for (cp = &chrdevs[i]; *cp; cp = &(*cp)->next)
if ((*cp)->major > major ||
((*cp)->major == major && (*cp)->baseminor >= baseminor))
break;
if (*cp && (*cp)->major == major &&
(*cp)->baseminor < baseminor + minorct) {
ret = -EBUSY;
goto out;
}
cd->next = *cp;
*cp = cd;
up(&chrdevs_lock);
return cd;
out:
up(&chrdevs_lock);
kfree(cd);
return ERR_PTR(ret);
}
static struct char_device_struct *
__unregister_chrdev_region(unsigned major, unsigned baseminor, int minorct)
{
struct char_device_struct *cd = NULL, **cp;
int i = major_to_index(major);
down(&chrdevs_lock);
for (cp = &chrdevs[i]; *cp; cp = &(*cp)->next)
if ((*cp)->major == major &&
(*cp)->baseminor == baseminor &&
(*cp)->minorct == minorct)
break;
if (*cp) {
cd = *cp;
*cp = cd->next;
}
up(&chrdevs_lock);
return cd;
}
int register_chrdev_region(dev_t from, unsigned count, const char *name)
{
struct char_device_struct *cd;
dev_t to = from + count;
dev_t n, next;
for (n = from; n < to; n = next) {
next = MKDEV(MAJOR(n)+1, 0);
if (next > to)
next = to;
cd = __register_chrdev_region(MAJOR(n), MINOR(n),
next - n, name);
if (IS_ERR(cd))
goto fail;
}
return 0;
fail:
to = n;
for (n = from; n < to; n = next) {
next = MKDEV(MAJOR(n)+1, 0);
kfree(__unregister_chrdev_region(MAJOR(n), MINOR(n), next - n));
}
return PTR_ERR(cd);
}
int alloc_chrdev_region(dev_t *dev, unsigned baseminor, unsigned count,
const char *name)
{
struct char_device_struct *cd;
cd = __register_chrdev_region(0, baseminor, count, name);
if (IS_ERR(cd))
return PTR_ERR(cd);
*dev = MKDEV(cd->major, cd->baseminor);
return 0;
}
int register_chrdev(unsigned int major, const char *name,
struct file_operations *fops)
{
struct char_device_struct *cd;
struct cdev *cdev;
char *s;
int err = -ENOMEM;
cd = __register_chrdev_region(major, 0, 256, name);
if (IS_ERR(cd))
return PTR_ERR(cd);
cdev = cdev_alloc();
if (!cdev)
goto out2;
cdev->owner = fops->owner;
cdev->ops = fops;
kobject_set_name(&cdev->kobj, "%s", name);
for (s = strchr(kobject_name(&cdev->kobj),'/'); s; s = strchr(s, '/'))
*s = '!';
err = cdev_add(cdev, MKDEV(cd->major, 0), 256);
if (err)
goto out;
cd->cdev = cdev;
return major ? 0 : cd->major;
out:
kobject_put(&cdev->kobj);
out2:
kfree(__unregister_chrdev_region(cd->major, 0, 256));
return err;
}
void unregister_chrdev_region(dev_t from, unsigned count)
{
dev_t to = from + count;
dev_t n, next;
for (n = from; n < to; n = next) {
next = MKDEV(MAJOR(n)+1, 0);
if (next > to)
next = to;
kfree(__unregister_chrdev_region(MAJOR(n), MINOR(n), next - n));
}
}
int unregister_chrdev(unsigned int major, const char *name)
{
struct char_device_struct *cd;
cd = __unregister_chrdev_region(major, 0, 256);
if (cd && cd->cdev)
cdev_del(cd->cdev);
kfree(cd);
return 0;
}
static DEFINE_SPINLOCK(cdev_lock);
static struct kobject *cdev_get(struct cdev *p)
{
struct module *owner = p->owner;
struct kobject *kobj;
if (owner && !try_module_get(owner))
return NULL;
kobj = kobject_get(&p->kobj);
if (!kobj)
module_put(owner);
return kobj;
}
void cdev_put(struct cdev *p)
{
if (p) {
struct module *owner = p->owner;
kobject_put(&p->kobj);
module_put(owner);
}
}
/*
* Called every time a character special file is opened
*/
int chrdev_open(struct inode * inode, struct file * filp)
{
struct cdev *p;
struct cdev *new = NULL;
int ret = 0;
spin_lock(&cdev_lock);
p = inode->i_cdev;
if (!p) {
struct kobject *kobj;
int idx;
spin_unlock(&cdev_lock);
kobj = kobj_lookup(cdev_map, inode->i_rdev, &idx);
if (!kobj)
return -ENXIO;
new = container_of(kobj, struct cdev, kobj);
spin_lock(&cdev_lock);
p = inode->i_cdev;
if (!p) {
inode->i_cdev = p = new;
inode->i_cindex = idx;
list_add(&inode->i_devices, &p->list);
new = NULL;
} else if (!cdev_get(p))
ret = -ENXIO;
} else if (!cdev_get(p))
ret = -ENXIO;
spin_unlock(&cdev_lock);
cdev_put(new);
if (ret)
return ret;
filp->f_op = fops_get(p->ops);
if (!filp->f_op) {
cdev_put(p);
return -ENXIO;
}
if (filp->f_op->open) {
lock_kernel();
ret = filp->f_op->open(inode,filp);
unlock_kernel();
}
if (ret)
cdev_put(p);
return ret;
}
void cd_forget(struct inode *inode)
{
spin_lock(&cdev_lock);
list_del_init(&inode->i_devices);
inode->i_cdev = NULL;
spin_unlock(&cdev_lock);
}
static void cdev_purge(struct cdev *cdev)
{
spin_lock(&cdev_lock);
while (!list_empty(&cdev->list)) {
struct inode *inode;
inode = container_of(cdev->list.next, struct inode, i_devices);
list_del_init(&inode->i_devices);
inode->i_cdev = NULL;
}
spin_unlock(&cdev_lock);
}
/*
* Dummy default file-operations: the only thing this does
* is contain the open that then fills in the correct operations
* depending on the special file...
*/
struct file_operations def_chr_fops = {
.open = chrdev_open,
};
static struct kobject *exact_match(dev_t dev, int *part, void *data)
{
struct cdev *p = data;
return &p->kobj;
}
static int exact_lock(dev_t dev, void *data)
{
struct cdev *p = data;
return cdev_get(p) ? 0 : -1;
}
int cdev_add(struct cdev *p, dev_t dev, unsigned count)
{
p->dev = dev;
p->count = count;
return kobj_map(cdev_map, dev, count, NULL, exact_match, exact_lock, p);
}
static void cdev_unmap(dev_t dev, unsigned count)
{
kobj_unmap(cdev_map, dev, count);
}
void cdev_del(struct cdev *p)
{
cdev_unmap(p->dev, p->count);
kobject_put(&p->kobj);
}
static void cdev_default_release(struct kobject *kobj)
{
struct cdev *p = container_of(kobj, struct cdev, kobj);
cdev_purge(p);
}
static void cdev_dynamic_release(struct kobject *kobj)
{
struct cdev *p = container_of(kobj, struct cdev, kobj);
cdev_purge(p);
kfree(p);
}
static struct kobj_type ktype_cdev_default = {
.release = cdev_default_release,
};
static struct kobj_type ktype_cdev_dynamic = {
.release = cdev_dynamic_release,
};
struct cdev *cdev_alloc(void)
{
struct cdev *p = kmalloc(sizeof(struct cdev), GFP_KERNEL);
if (p) {
memset(p, 0, sizeof(struct cdev));
p->kobj.ktype = &ktype_cdev_dynamic;
INIT_LIST_HEAD(&p->list);
kobject_init(&p->kobj);
}
return p;
}
void cdev_init(struct cdev *cdev, struct file_operations *fops)
{
memset(cdev, 0, sizeof *cdev);
INIT_LIST_HEAD(&cdev->list);
cdev->kobj.ktype = &ktype_cdev_default;
kobject_init(&cdev->kobj);
cdev->ops = fops;
}
static struct kobject *base_probe(dev_t dev, int *part, void *data)
{
if (request_module("char-major-%d-%d", MAJOR(dev), MINOR(dev)) > 0)
/* Make old-style 2.4 aliases work */
request_module("char-major-%d", MAJOR(dev));
return NULL;
}
void __init chrdev_init(void)
{
cdev_map = kobj_map_init(base_probe, &chrdevs_lock);
}
/* Let modules do char dev stuff */
EXPORT_SYMBOL(register_chrdev_region);
EXPORT_SYMBOL(unregister_chrdev_region);
EXPORT_SYMBOL(alloc_chrdev_region);
EXPORT_SYMBOL(cdev_init);
EXPORT_SYMBOL(cdev_alloc);
EXPORT_SYMBOL(cdev_del);
EXPORT_SYMBOL(cdev_add);
EXPORT_SYMBOL(register_chrdev);
EXPORT_SYMBOL(unregister_chrdev);
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