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tty: Don't take tty_mutex for tty count changes

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Holding tty_mutex is no longer required to serialize changes to
the tty_count or to prevent concurrent opens of closing ttys;
tty_lock() is sufficient.

Reviewed-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Peter Hurley 2014-11-05 12:12:53 -05:00 committed by Greg Kroah-Hartman
parent 04980706c8
commit 0911261d4c
1 changed files with 0 additions and 6 deletions
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6
drivers/tty/tty_io.c
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@ -1804,10 +1804,6 @@ int tty_release(struct inode *inode, struct file *filp)
* each iteration we avoid any problems. * each iteration we avoid any problems.
*/ */
while (1) { while (1) {
/* Guard against races with tty->count changes elsewhere and
opens on /dev/tty */
mutex_lock(&tty_mutex);
tty_lock_pair(tty, o_tty); tty_lock_pair(tty, o_tty);
tty_closing = tty->count <= 1; tty_closing = tty->count <= 1;
o_tty_closing = o_tty && o_tty_closing = o_tty &&
@ -1840,7 +1836,6 @@ int tty_release(struct inode *inode, struct file *filp)
printk(KERN_WARNING "%s: %s: read/write wait queue active!\n", printk(KERN_WARNING "%s: %s: read/write wait queue active!\n",
__func__, tty_name(tty, buf)); __func__, tty_name(tty, buf));
tty_unlock_pair(tty, o_tty); tty_unlock_pair(tty, o_tty);
mutex_unlock(&tty_mutex);
schedule(); schedule();
} }
@ -1891,7 +1886,6 @@ int tty_release(struct inode *inode, struct file *filp)
read_unlock(&tasklist_lock); read_unlock(&tasklist_lock);
} }
mutex_unlock(&tty_mutex);
tty_unlock_pair(tty, o_tty); tty_unlock_pair(tty, o_tty);
/* At this point, the tty->count == 0 should ensure a dead tty /* At this point, the tty->count == 0 should ensure a dead tty
cannot be re-opened by a racing opener */ cannot be re-opened by a racing opener */