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DAHDI-linux: Fix "surprise removal" problems

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* Added a nodev_*() file_operations that handle system calls
  from user-space after surprise device removal.

Signed-off-by: Oron Peled <oron.peled@xorcom.com>
Acked-by: Tzafrir Cohen <tzafrir.cohen@xorcom.com>
Acked-by: Shaun Ruffell <sruffell@digium.com>

git-svn-id: http://svn.asterisk.org/svn/dahdi/linux/trunk@10381 a0bf4364-ded3-4de4-8d8a-66a801d63aff
This commit is contained in:
Oron Peled
2011-12-14 19:27:27 +00:00
committed by Tzafrir Cohen
parent 6b6d047241
commit 2b11667c47
1 changed files with 122 additions and 29 deletions
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151
drivers/dahdi/dahdi-base.c
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@@ -2150,6 +2150,8 @@ static unsigned long _chan_cleanup(struct dahdi_chan *pos, unsigned long data)
return 0;
}
static const struct file_operations nodev_fops;
static void dahdi_chan_unreg(struct dahdi_chan *chan)
{
unsigned long flags;
@@ -2164,6 +2166,11 @@ static void dahdi_chan_unreg(struct dahdi_chan *chan)
"%s: surprise removal: chan %d\n",
__func__, chan->channo);
chan->file->private_data = NULL;
chan->file->f_op = &nodev_fops;
/*
* From now on, any file_operations for this device
* would call the nodev_fops methods.
*/
}
spin_lock_irqsave(&chan->lock, flags);
@@ -2240,14 +2247,12 @@ static ssize_t dahdi_chan_read(struct file *file, char __user *usrbuf,
count &= 0xffff;
if (unlikely(!chan)) {
/* We would typically be here because of surprise hardware
* removal or driver unbinding while a user space application
* has a channel open. Most telephony applications are run at
* elevated priorities so this sleep can prevent the high
* priority threads from consuming the CPU if they're not
* expecting surprise device removal.
/*
* This should never happen. Surprise device removal
* should lead us to the nodev_* file_operations
*/
msleep(5);
module_printk(KERN_ERR, "%s: NODEV\n", __func__);
return -ENODEV;
}
@@ -2363,14 +2368,12 @@ static ssize_t dahdi_chan_write(struct file *file, const char __user *usrbuf,
count &= 0xffff;
if (unlikely(!chan)) {
/* We would typically be here because of surprise hardware
* removal or driver unbinding while a user space application
* has a channel open. Most telephony applications are run at
* elevated priorities so this sleep can prevent the high
* priority threads from consuming the CPU if they're not
* expecting surprise device removal.
/*
* This should never happen. Surprise device removal
* should lead us to the nodev_* file_operations
*/
msleep(5);
module_printk(KERN_ERR, "%s: NODEV\n", __func__);
return -ENODEV;
}
@@ -5500,13 +5503,12 @@ static int dahdi_ioctl_iomux(struct file *file, unsigned long data)
wait_result = 0;
prepare_to_wait(&chan->waitq, &wait, TASK_INTERRUPTIBLE);
if (unlikely(!chan->file->private_data)) {
static int rate_limit;
if ((rate_limit++ % 1000) == 0)
module_printk(KERN_NOTICE,
"%s: (%d) nodev\n",
__func__, rate_limit);
/*
* This should never happen. Surprise device removal
* should lead us to the nodev_* file_operations
*/
msleep(5);
module_printk(KERN_ERR, "%s: NODEV\n", __func__);
ret = -ENODEV;
break;
}
@@ -9171,12 +9173,12 @@ static unsigned int dahdi_timer_poll(struct file *file, struct poll_table_struct
ret |= POLLPRI;
spin_unlock_irqrestore(&dahdi_timer_lock, flags);
} else {
static int rate_limit;
if ((rate_limit++ % 1000) == 0)
module_printk(KERN_NOTICE, "%s: (%d) nodev\n",
__func__, rate_limit);
/*
* This should never happen. Surprise device removal
* should lead us to the nodev_* file_operations
*/
msleep(5);
module_printk(KERN_ERR, "%s: NODEV\n", __func__);
return POLLERR | POLLHUP | POLLRDHUP | POLLNVAL | POLLPRI;
}
return ret;
@@ -9191,12 +9193,12 @@ dahdi_chan_poll(struct file *file, struct poll_table_struct *wait_table)
unsigned long flags;
if (unlikely(!c)) {
static int rate_limit;
if ((rate_limit++ % 1000) == 0)
module_printk(KERN_NOTICE, "%s: (%d) nodev\n",
__func__, rate_limit);
msleep(20);
/*
* This should never happen. Surprise device removal
* should lead us to the nodev_* file_operations
*/
msleep(5);
module_printk(KERN_ERR, "%s: NODEV\n", __func__);
return POLLERR | POLLHUP | POLLRDHUP | POLLNVAL | POLLPRI;
}
@@ -9833,6 +9835,97 @@ static const struct file_operations dahdi_fops = {
.poll = dahdi_poll,
};
/*
* DAHDI stability should not depend on the calling process behaviour.
* In case of suprise device removal, we should be able to return
* sane results (-ENODEV) even after the underlying device was released.
*
* This should be OK even if the calling process (hint, hint Asterisk)
* ignores the system calls return value.
*
* We simply use dummy file_operations to implement this.
*/
/*
* Common behaviour called from all other nodev_*() file_operations
*/
static int nodev_common(const char msg[])
{
if (printk_ratelimit()) {
module_printk(KERN_NOTICE,
"nodev: %s: process %d still calling\n",
msg, current->tgid);
}
msleep(5);
return -ENODEV;
}
static ssize_t nodev_chan_read(struct file *file, char __user *usrbuf,
size_t count, loff_t *ppos)
{
return nodev_common("read");
}
static ssize_t nodev_chan_write(struct file *file, const char __user *usrbuf,
size_t count, loff_t *ppos)
{
return nodev_common("write");
}
static unsigned int
nodev_chan_poll(struct file *file, struct poll_table_struct *wait_table)
{
return nodev_common("poll");
}
static long
nodev_unlocked_ioctl(struct file *file, unsigned int cmd, unsigned long data)
{
switch (cmd) {
case DAHDI_GETEVENT: /* Get event on queue */
/*
* Hint the bugger that the channel is gone for good
*/
put_user(DAHDI_EVENT_REMOVED, (int __user *)data);
break;
}
return nodev_common("ioctl");
}
#ifndef HAVE_UNLOCKED_IOCTL
static int nodev_ioctl(struct inode *inode, struct file *file,
unsigned int cmd, unsigned long data)
{
return nodev_unlocked_ioctl(file, cmd, data);
}
#endif
#ifdef HAVE_COMPAT_IOCTL
static long nodev_ioctl_compat(struct file *file, unsigned int cmd,
unsigned long data)
{
if (cmd == DAHDI_SFCONFIG)
return -ENOTTY; /* Not supported yet */
return nodev_unlocked_ioctl(file, cmd, data);
}
#endif
static const struct file_operations nodev_fops = {
.owner = THIS_MODULE,
#ifdef HAVE_UNLOCKED_IOCTL
.unlocked_ioctl = nodev_unlocked_ioctl,
#ifdef HAVE_COMPAT_IOCTL
.compat_ioctl = nodev_ioctl_compat,
#endif
#else
.ioctl = nodev_ioctl,
#endif
.read = nodev_chan_read,
.write = nodev_chan_write,
.poll = nodev_chan_poll,
};
static const struct file_operations dahdi_chan_fops = {
.owner = THIS_MODULE,
.open = dahdi_open,