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Date: Wed, 5 May 2010 00:33:50 +0200
From: Arnd Bergmann <arnd@...db.de>
To: linux-kernel@...r.kernel.org
Cc: Arnd Bergmann <arnd@...db.de>, Alan Cox <alan@...rguk.ukuu.org.uk>,
Greg KH <gregkh@...e.de>,
Frederic Weisbecker <fweisbec@...il.com>,
Thomas Gleixner <tglx@...utronix.de>,
Andrew Morton <akpm@...ux-foundation.org>,
John Kacur <jkacur@...hat.com>,
Al Viro <viro@...iv.linux.org.uk>, Ingo Molnar <mingo@...e.hu>
Subject: [PATCH 11/13] tty: remove tty_lock_nested
This changes all remaining users of tty_lock_nested
to be non-recursive, which lets us kill this function.
As a consequence, we won't need to keep the lock count
any more, which allows more simplifications later.
Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
drivers/char/pty.c | 2 +-
drivers/char/selection.c | 4 ++--
drivers/char/tty_io.c | 41 ++++++++++++++++++++---------------------
drivers/char/tty_ldisc.c | 3 +--
drivers/char/tty_mutex.c | 15 ---------------
drivers/serial/crisv10.c | 7 ++++---
include/linux/tty.h | 17 +----------------
7 files changed, 29 insertions(+), 60 deletions(-)
diff --git a/drivers/char/pty.c b/drivers/char/pty.c
index 889de89..76de961 100644
--- a/drivers/char/pty.c
+++ b/drivers/char/pty.c
@@ -62,7 +62,7 @@ static void pty_close(struct tty_struct *tty, struct file *filp)
if (tty->driver == ptm_driver)
devpts_pty_kill(tty->link);
#endif
- tty_vhangup(tty->link);
+ tty_vhangup_locked(tty->link);
}
}
diff --git a/drivers/char/selection.c b/drivers/char/selection.c
index 85211a3..8e314bb 100644
--- a/drivers/char/selection.c
+++ b/drivers/char/selection.c
@@ -313,7 +313,8 @@ int paste_selection(struct tty_struct *tty)
struct tty_ldisc *ld;
DECLARE_WAITQUEUE(wait, current);
- tty_lock_nested(); /* always called with BTM from vt_ioctl */
+ /* always called with BTM from vt_ioctl */
+ WARN_ON(!tty_locked());
acquire_console_sem();
poke_blanked_console();
@@ -338,6 +339,5 @@ int paste_selection(struct tty_struct *tty)
__set_current_state(TASK_RUNNING);
tty_ldisc_deref(ld);
- tty_unlock();
return 0;
}
diff --git a/drivers/char/tty_io.c b/drivers/char/tty_io.c
index e1b2fca..4e16b34 100644
--- a/drivers/char/tty_io.c
+++ b/drivers/char/tty_io.c
@@ -492,10 +492,8 @@ EXPORT_SYMBOL_GPL(tty_wakeup);
* tasklist_lock to walk task list for hangup event
* ->siglock to protect ->signal/->sighand
*/
-static void do_tty_hangup(struct work_struct *work)
+void tty_vhangup_locked(struct tty_struct *tty)
{
- struct tty_struct *tty =
- container_of(work, struct tty_struct, hangup_work);
struct file *cons_filp = NULL;
struct file *filp, *f = NULL;
struct task_struct *p;
@@ -517,8 +515,6 @@ static void do_tty_hangup(struct work_struct *work)
/* inuse_filps is protected by the single tty lock,
this really needs to change if we want to flush the
workqueue with the lock held */
- tty_lock_nested(); /* called with BTM held from pty_close and
- others */
check_tty_count(tty, "do_tty_hangup");
file_list_lock();
@@ -598,11 +594,20 @@ static void do_tty_hangup(struct work_struct *work)
*/
set_bit(TTY_HUPPED, &tty->flags);
tty_ldisc_enable(tty);
- tty_unlock();
if (f)
fput(f);
}
+static void do_tty_hangup(struct work_struct *work)
+{
+ struct tty_struct *tty =
+ container_of(work, struct tty_struct, hangup_work);
+
+ tty_lock();
+ tty_vhangup_locked(tty);
+ tty_unlock();
+}
+
/**
* tty_hangup - trigger a hangup event
* @tty: tty to hangup
@@ -638,7 +643,9 @@ void tty_vhangup(struct tty_struct *tty)
printk(KERN_DEBUG "%s vhangup...\n", tty_name(tty, buf));
#endif
- do_tty_hangup(&tty->hangup_work);
+ tty_lock();
+ tty_vhangup_locked(tty);
+ tty_unlock();
}
EXPORT_SYMBOL(tty_vhangup);
@@ -719,10 +726,12 @@ void disassociate_ctty(int on_exit)
tty = get_current_tty();
if (tty) {
tty_pgrp = get_pid(tty->pgrp);
- tty_lock_nested(); /* see above */
- if (on_exit && tty->driver->type != TTY_DRIVER_TYPE_PTY)
- tty_vhangup(tty);
- tty_unlock();
+ if (on_exit) {
+ tty_lock();
+ if (tty->driver->type != TTY_DRIVER_TYPE_PTY)
+ tty_vhangup_locked(tty);
+ tty_unlock();
+ }
tty_kref_put(tty);
} else if (on_exit) {
struct pid *old_pgrp;
@@ -1218,18 +1227,14 @@ static int tty_driver_install_tty(struct tty_driver *driver,
int ret;
if (driver->ops->install) {
- tty_lock_nested(); /* already called with BTM held */
ret = driver->ops->install(driver, tty);
- tty_unlock();
return ret;
}
if (tty_init_termios(tty) == 0) {
- tty_lock_nested();
tty_driver_kref_get(driver);
tty->count++;
driver->ttys[idx] = tty;
- tty_unlock();
return 0;
}
return -ENOMEM;
@@ -1322,15 +1327,11 @@ struct tty_struct *tty_init_dev(struct tty_driver *driver, int idx,
struct tty_struct *tty;
int retval;
- tty_lock_nested(); /* always called with tty lock held already */
-
/* Check if pty master is being opened multiple times */
if (driver->subtype == PTY_TYPE_MASTER &&
(driver->flags & TTY_DRIVER_DEVPTS_MEM) && !first_ok) {
- tty_unlock();
return ERR_PTR(-EIO);
}
- tty_unlock();
/*
* First time open is complex, especially for PTY devices.
@@ -1374,9 +1375,7 @@ release_mem_out:
if (printk_ratelimit())
printk(KERN_INFO "tty_init_dev: ldisc open failed, "
"clearing slot %d\n", idx);
- tty_lock_nested();
release_tty(tty, idx);
- tty_unlock();
return ERR_PTR(retval);
}
diff --git a/drivers/char/tty_ldisc.c b/drivers/char/tty_ldisc.c
index d4259cf..c71a94a 100644
--- a/drivers/char/tty_ldisc.c
+++ b/drivers/char/tty_ldisc.c
@@ -458,9 +458,8 @@ static int tty_ldisc_open(struct tty_struct *tty, struct tty_ldisc *ld)
if (ld->ops->open) {
int ret;
/* BTM here locks versus a hangup event */
- tty_lock_nested(); /* always held here already */
+ WARN_ON(!tty_locked());
ret = ld->ops->open(tty);
- tty_unlock();
return ret;
}
return 0;
diff --git a/drivers/char/tty_mutex.c b/drivers/char/tty_mutex.c
index 51e0852..6bd47e1 100644
--- a/drivers/char/tty_mutex.c
+++ b/drivers/char/tty_mutex.c
@@ -73,21 +73,6 @@ void __lockfunc tty_lock(void)
}
EXPORT_SYMBOL(tty_lock);
-void __lockfunc tty_lock_nested(void)
-{
- struct task_struct *task = current;
- int depth = task->tty_lock_depth + 1;
-
- if (likely(!depth))
- /*
- * No recursion worries - we set up tty_lock_depth _after_
- */
- mutex_lock(&big_tty_mutex);
-
- task->tty_lock_depth = depth;
-}
-EXPORT_SYMBOL(tty_lock_nested);
-
void __lockfunc tty_unlock(void)
{
struct task_struct *task = current;
diff --git a/drivers/serial/crisv10.c b/drivers/serial/crisv10.c
index 9047384..28ff46a 100644
--- a/drivers/serial/crisv10.c
+++ b/drivers/serial/crisv10.c
@@ -3254,9 +3254,10 @@ rs_write(struct tty_struct *tty,
*/
/* Sleep until all sent */
- tty_lock_nested();
- tty_wait_until_sent_locked(tty, 0);
- tty_unlock();
+ if (tty_locked())
+ tty_wait_until_sent_locked(tty, 0);
+ else
+ tty_wait_until_sent(tty, 0);
#ifdef CONFIG_ETRAX_FAST_TIMER
/* Now sleep a little more so that shift register is empty */
schedule_usleep(info->char_time_usec * 2);
diff --git a/include/linux/tty.h b/include/linux/tty.h
index 8ddd952..3cf4556 100644
--- a/include/linux/tty.h
+++ b/include/linux/tty.h
@@ -416,6 +416,7 @@ extern int is_ignored(int sig);
extern int tty_signal(int sig, struct tty_struct *tty);
extern void tty_hangup(struct tty_struct *tty);
extern void tty_vhangup(struct tty_struct *tty);
+extern void tty_vhangup_locked(struct tty_struct *tty);
extern void tty_vhangup_self(void);
extern void tty_unhangup(struct file *filp);
extern int tty_hung_up_p(struct file *filp);
@@ -575,19 +576,7 @@ extern long vt_compat_ioctl(struct tty_struct *tty, struct file * file,
/* tty_mutex.c */
/* functions for preparation of BKL removal */
-
-/*
- * tty_lock_nested get the tty_lock while potentially holding it
- *
- * The Big TTY Mutex is a recursive lock, meaning you can take it
- * from a thread that is already holding it.
- * This is bad for a number of reasons, so tty_lock_nested should
- * really be used as rarely as possible. If a code location can
- * be shown to never get called with this held already, it should
- * use tty_lock() instead.
- */
#ifdef CONFIG_TTY_MUTEX
-extern void __lockfunc tty_lock_nested(void) __acquires(tty_lock);
extern void __lockfunc tty_lock(void) __acquires(tty_lock);
extern void __lockfunc tty_unlock(void) __releases(tty_lock);
#define tty_locked() (current->tty_lock_depth >= 0)
@@ -602,10 +591,6 @@ void __lockfunc __release_tty_lock(void);
__reacquire_tty_lock() : 0 )
#else
-static inline void __lockfunc tty_lock_nested(void) __acquires(kernel_lock)
-{
- lock_kernel();
-}
static inline void tty_lock(void) __acquires(kernel_lock)
{
WARN_ON(kernel_locked());
--
1.7.0.4
--
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