From: Sukadev Bhattiprolu <[EMAIL PROTECTED]>
Subject: [RFC][PATCH 2/3] Move some init_dev() code to callers
init_dev() tries to find a tty and if it finds an existing tty, does
a 'fast' open. If its not an existing tty, init_dev does a slower
first time open requiring allocation and complex initialization.
All these seem to make the code more complex. When opening /dev/tty,
the caller already has the tty so there is no need to find it. Further
the fast and slow opens in init_dev() don't really share much code
and could be in separate functions.
With only two callers, init_dev() does not really need to be that
generalized and some of the pieces can be moved into the callers.
---
drivers/char/tty_io.c | 71 +++++++++++++++++++++++++++++++++-----------------
1 file changed, 47 insertions(+), 24 deletions(-)
Index: linux-next/drivers/char/tty_io.c
===================================================================
--- linux-next.orig/drivers/char/tty_io.c 2008-08-25 12:31:15.000000000
-0700
+++ linux-next/drivers/char/tty_io.c 2008-08-25 12:54:35.000000000 -0700
@@ -1322,20 +1322,6 @@ static int init_dev(struct tty_driver *d
struct ktermios *ltp, **ltp_loc, *o_ltp, **o_ltp_loc;
int retval = 0;
- tty = find_tty(driver, idx);
- if (IS_ERR(tty)) {
- retval = PTR_ERR(tty);
- goto end_init;
- }
-
- if (tty) {
- retval = fast_tty_open(tty);
- if (retval)
- return retval;
- *ret_tty = tty;
- return 0;
- }
-
/* Check if pty master is being opened multiple times */
if (driver->subtype == PTY_TYPE_MASTER &&
(driver->flags & TTY_DRIVER_DEVPTS_MEM) && !first_ok) {
@@ -1476,9 +1462,7 @@ static int init_dev(struct tty_driver *d
if (retval)
goto release_mem_out;
- goto success;
-success:
*ret_tty = tty;
/* All paths come through here to release the mutex */
@@ -1853,14 +1837,15 @@ static void release_dev(struct file *fil
* The termios state of a pty is reset on first open so that
* settings don't persist across reuse.
*
- * Locking: tty_mutex protects tty, get_tty_driver and init_dev work.
+ * Locking: tty_mutex protects tty, get_tty_driver, find_tty,
+ * fast_tty_open and init_dev work.
* tty->count should protect the rest.
* ->siglock protects ->signal/->sighand
*/
static int __tty_open(struct inode *inode, struct file *filp)
{
- struct tty_struct *tty;
+ struct tty_struct *tty = NULL;
int noctty, retval;
struct tty_driver *driver;
int index;
@@ -1917,8 +1902,19 @@ retry_open:
return -ENODEV;
}
got_driver:
- retval = init_dev(driver, index, &tty, 0);
+ if (!tty) {
+ tty = find_tty(driver, index);
+ if (IS_ERR(tty))
+ return PTR_ERR(tty);
+ }
+
+ if (tty)
+ retval = fast_tty_open(tty);
+ else
+ retval = init_dev(driver, index, &tty, 0);
+
mutex_unlock(&tty_mutex);
+
if (retval)
return retval;
@@ -1986,8 +1982,24 @@ static int tty_open(struct inode *inode,
}
-
#ifdef CONFIG_UNIX98_PTYS
+
+static struct tty_struct *find_open_tty(struct tty_driver *driver, int index)
+{
+ int retval;
+ struct tty_struct *tty;
+
+ tty = find_tty(driver, index);
+ if (!tty || IS_ERR(tty))
+ return tty;
+
+ retval = fast_tty_open(tty);
+ if (retval)
+ tty = ERR_PTR(retval);
+
+ return tty;
+}
+
/**
* ptmx_open - open a unix 98 pty master
* @inode: inode of device file
@@ -1995,15 +2007,15 @@ static int tty_open(struct inode *inode,
*
* Allocate a unix98 pty master device from the ptmx driver.
*
- * Locking: tty_mutex protects theinit_dev work. tty->count should
- * protect the rest.
+ * Locking: tty_mutex protects the find_open_tty and init_dev work.
+ * tty->count should protect the rest.
* allocated_ptys_lock handles the list of free pty numbers
*/
static int __ptmx_open(struct inode *inode, struct file *filp)
{
struct tty_struct *tty;
- int retval;
+ int retval = 0;
int index;
nonseekable_open(inode, filp);
@@ -2014,7 +2026,18 @@ static int __ptmx_open(struct inode *ino
return index;
mutex_lock(&tty_mutex);
- retval = init_dev(ptm_driver, index, &tty, 1);
+
+ /*
+ * TODO: We just allocated the index, will find_open_tty() ever
+ * find a tty ? Keep the find for now for compatiblity with
+ * old init_dev().
+ */
+ tty = find_open_tty(ptm_driver, index);
+ if (IS_ERR(tty))
+ retval = PTR_ERR(tty);
+ else if (!tty)
+ retval = init_dev(ptm_driver, index, &tty, 1);
+
mutex_unlock(&tty_mutex);
if (retval)
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