[svn-commits] sruffell: branch linux/sruffell/chan_list_refactoring r9255 - /linux/team/sru...
SVN commits to the Digium repositories
svn-commits at lists.digium.com
Thu Sep 2 12:40:50 CDT 2010
Author: sruffell
Date: Thu Sep 2 12:40:45 2010
New Revision: 9255
URL: http://svnview.digium.com/svn/dahdi?view=rev&rev=9255
Log:
dahdi: Be more tolerant of surprise removal of channels.
Enable DAHDI to detect if an operation on a file handle refers to a
channel that may have been unregistered. This can occur, for example,
when a board driver is hot-swapped out in a live system.
This patch ensures that file->private_data is always properly set for
any open channel, and it's set back to NULL when a channel is
unregistered. This way file->private_data can be used to check whether
it's valid to perform an operation on the channel. (NOTE: There is
still a race condition here if the driver was unbound on one processor
during the window of time between when file->private_data was checked
and the system call finishes).
Also, since DAHDI should only return -ENODEV on read or write when there
was a surprise device removal on a running system this sleep can prevent
the system from becoming unresponsive if the userspace application does
not check for the -ENODEV error and constantly tries to call read with
elevated privileges.
(issue #17669)
Reported by: tzafrir
Tested by: sruffell
Signed-off-by: Shaun Ruffell <sruffell at digium.com>
Modified:
linux/team/sruffell/chan_list_refactoring/drivers/dahdi/dahdi-base.c
Modified: linux/team/sruffell/chan_list_refactoring/drivers/dahdi/dahdi-base.c
URL: http://svnview.digium.com/svn/dahdi/linux/team/sruffell/chan_list_refactoring/drivers/dahdi/dahdi-base.c?view=diff&rev=9255&r1=9254&r2=9255
==============================================================================
--- linux/team/sruffell/chan_list_refactoring/drivers/dahdi/dahdi-base.c (original)
+++ linux/team/sruffell/chan_list_refactoring/drivers/dahdi/dahdi-base.c Thu Sep 2 12:40:45 2010
@@ -2000,6 +2000,15 @@
might_sleep();
+ /* In the case of surprise removal of hardware, make sure any open
+ * file handles to this channel are disassociated with the actual
+ * dahdi_chan. */
+ if (chan->file) {
+ chan->file->private_data = NULL;
+ if (chan->span)
+ module_put(chan->span->ops->owner);
+ }
+
release_echocan(chan->ec_factory);
#ifdef CONFIG_DAHDI_NET
@@ -2053,9 +2062,10 @@
write_unlock_irqrestore(&chan_lock, flags);
}
-static ssize_t dahdi_chan_read(struct file *file, char __user *usrbuf, size_t count, int unit)
-{
- struct dahdi_chan *chan = chans[unit];
+static ssize_t dahdi_chan_read(struct file *file, char __user *usrbuf,
+ size_t count)
+{
+ struct dahdi_chan *chan = file->private_data;
int amnt;
int res, rv;
int oldbuf,x;
@@ -2064,10 +2074,19 @@
/* Make sure count never exceeds 65k, and make sure it's unsigned */
count &= 0xffff;
- if (!chan)
- return -EINVAL;
-
- if (count < 1)
+ 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.
+ */
+ msleep(5);
+ return -ENODEV;
+ }
+
+ if (unlikely(count < 1))
return -EINVAL;
for (;;) {
@@ -2179,19 +2198,29 @@
return range1 + range2;
}
-static ssize_t dahdi_chan_write(struct file *file, const char __user *usrbuf, size_t count, int unit)
+static ssize_t dahdi_chan_write(struct file *file, const char __user *usrbuf,
+ size_t count)
{
unsigned long flags;
- struct dahdi_chan *chan = chans[unit];
+ struct dahdi_chan *chan = file->private_data;
int res, amnt, oldbuf, rv, x;
/* Make sure count never exceeds 65k, and make sure it's unsigned */
count &= 0xffff;
- if (!chan)
- return -EINVAL;
-
- if (count < 1) {
+ 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.
+ */
+ msleep(5);
+ return -ENODEV;
+ }
+
+ if (unlikely(count < 1)) {
return -EINVAL;
}
@@ -2777,6 +2806,7 @@
}
if (!res) {
chan->file = file;
+ file->private_data = chan;
spin_unlock_irqrestore(&chan->lock, flags);
} else {
spin_unlock_irqrestore(&chan->lock, flags);
@@ -2941,7 +2971,7 @@
chan = file->private_data;
if (!chan)
return -EINVAL;
- return dahdi_chan_read(file, usrbuf, count, chan->channo);
+ return dahdi_chan_read(file, usrbuf, count);
}
if (unit == 255) {
@@ -2950,12 +2980,12 @@
module_printk(KERN_NOTICE, "No pseudo channel structure to read?\n");
return -EINVAL;
}
- return dahdi_chan_read(file, usrbuf, count, chan->channo);
+ return dahdi_chan_read(file, usrbuf, count);
}
if (count < 0)
return -EINVAL;
- return dahdi_chan_read(file, usrbuf, count, unit);
+ return dahdi_chan_read(file, usrbuf, count);
}
static ssize_t dahdi_write(struct file *file, const char __user *usrbuf, size_t count, loff_t *ppos)
@@ -2973,7 +3003,7 @@
chan = file->private_data;
if (!chan)
return -EINVAL;
- return dahdi_chan_write(file, usrbuf, count, chan->channo);
+ return dahdi_chan_write(file, usrbuf, count);
}
if (unit == 255) {
chan = file->private_data;
@@ -2981,9 +3011,9 @@
module_printk(KERN_NOTICE, "No pseudo channel structure to read?\n");
return -EINVAL;
}
- return dahdi_chan_write(file, usrbuf, count, chan->channo);
- }
- return dahdi_chan_write(file, usrbuf, count, unit);
+ return dahdi_chan_write(file, usrbuf, count);
+ }
+ return dahdi_chan_write(file, usrbuf, count);
}
@@ -5913,6 +5943,12 @@
ret = dahdi_chanandpseudo_ioctl(file, cmd, data, chan->channo);
goto unlock_exit;
}
+
+ if (!file->private_data) {
+ ret = -ENXIO;
+ goto unlock_exit;
+ }
+
ret = dahdi_chan_ioctl(file, cmd, data, unit);
unlock_exit:
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