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SubjectRe: [GIT PATCH] TTY patches for 2.6.33-git

* Ingo Molnar <mingo@elte.hu> wrote:

>
> * Andrew Morton <akpm@linux-foundation.org> wrote:
>
> > Have a trace. I'm actually wondering if perhaps there's a missing
> > unlock_kernel() somewhere else, and the tty code is just the victim of
> > that.
>
> Unlikely i'd say. I have 1000+ successful overnight tests on the latest
> tree Linus pushed out:
>
> 3ef884b: Merge branch 'drm-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/airlied/d
>
> So that's a guaranteed 'good' kernel.
>
> The moment i merged 053fe57 into -tip the lockups started, so that's a
> guaranteed 'bad' kernel. There's only the TTY changes between those two
> points that look remotely related.
>
> It's spurious though so quite hard to bisect. I tried one bisection
> today already and it got on the wrong track. I'll do a brute-force
> revert of the commits i quoted, lets see what happens.

i'm testing the series of 5 reverts below. It's looking good so far. You
might want to try them - how quickly can you reproduce the hangs?

Ingo

--------------->
From 95b532d4e2f9a82c1dedf7ea4a6c2702402237e6 Mon Sep 17 00:00:00 2001
From: Ingo Molnar <mingo@elte.hu>
Date: Sat, 12 Dec 2009 11:08:04 +0100
Subject: [PATCH] Revert "tty: push the BKL down into the handlers a bit"
This reverts commit eeb89d918c2fa2b809e464136bbafdaec2aacb30.

diff --git a/drivers/char/pty.c b/drivers/char/pty.c
index 385c44b..d86c0bc 100644
--- a/drivers/char/pty.c
+++ b/drivers/char/pty.c
@@ -659,7 +659,7 @@ static int __ptmx_open(struct inode *inode, struct file *filp)
if (!retval)
return 0;
out1:
- tty_release(inode, filp);
+ tty_release_dev(filp);
return retval;
out:
devpts_kill_index(inode, index);
diff --git a/drivers/char/tty_io.c b/drivers/char/tty_io.c
index 1e24130..59499ee 100644
--- a/drivers/char/tty_io.c
+++ b/drivers/char/tty_io.c
@@ -142,6 +142,7 @@ ssize_t redirected_tty_write(struct file *, const char __user *,
size_t, loff_t *);
static unsigned int tty_poll(struct file *, poll_table *);
static int tty_open(struct inode *, struct file *);
+static int tty_release(struct inode *, struct file *);
long tty_ioctl(struct file *file, unsigned int cmd, unsigned long arg);
#ifdef CONFIG_COMPAT
static long tty_compat_ioctl(struct file *file, unsigned int cmd,
@@ -1016,16 +1017,14 @@ out:

void tty_write_message(struct tty_struct *tty, char *msg)
{
+ lock_kernel();
if (tty) {
mutex_lock(&tty->atomic_write_lock);
- lock_kernel();
- if (tty->ops->write && !test_bit(TTY_CLOSING, &tty->flags)) {
- unlock_kernel();
+ if (tty->ops->write && !test_bit(TTY_CLOSING, &tty->flags))
tty->ops->write(tty, msg, strlen(msg));
- } else
- unlock_kernel();
tty_write_unlock(tty);
}
+ unlock_kernel();
return;
}

@@ -1203,21 +1202,14 @@ static int tty_driver_install_tty(struct tty_driver *driver,
struct tty_struct *tty)
{
int idx = tty->index;
- int ret;

- if (driver->ops->install) {
- lock_kernel();
- ret = driver->ops->install(driver, tty);
- unlock_kernel();
- return ret;
- }
+ if (driver->ops->install)
+ return driver->ops->install(driver, tty);

if (tty_init_termios(tty) == 0) {
- lock_kernel();
tty_driver_kref_get(driver);
tty->count++;
driver->ttys[idx] = tty;
- unlock_kernel();
return 0;
}
return -ENOMEM;
@@ -1310,14 +1302,10 @@ struct tty_struct *tty_init_dev(struct tty_driver *driver, int idx,
struct tty_struct *tty;
int retval;

- lock_kernel();
/* Check if pty master is being opened multiple times */
if (driver->subtype == PTY_TYPE_MASTER &&
- (driver->flags & TTY_DRIVER_DEVPTS_MEM) && !first_ok) {
- unlock_kernel();
+ (driver->flags & TTY_DRIVER_DEVPTS_MEM) && !first_ok)
return ERR_PTR(-EIO);
- }
- unlock_kernel();

/*
* First time open is complex, especially for PTY devices.
@@ -1347,9 +1335,8 @@ struct tty_struct *tty_init_dev(struct tty_driver *driver, int idx,
* If we fail here just call release_tty to clean up. No need
* to decrement the use counts, as release_tty doesn't care.
*/
- lock_kernel();
+
retval = tty_ldisc_setup(tty, tty->link);
- unlock_kernel();
if (retval)
goto release_mem_out;
return tty;
@@ -1363,9 +1350,7 @@ release_mem_out:
if (printk_ratelimit())
printk(KERN_INFO "tty_init_dev: ldisc open failed, "
"clearing slot %d\n", idx);
- lock_kernel();
release_tty(tty, idx);
- unlock_kernel();
return ERR_PTR(retval);
}

@@ -1479,17 +1464,7 @@ static void release_tty(struct tty_struct *tty, int idx)
tty_kref_put(tty);
}

-/**
- * tty_release - vfs callback for close
- * @inode: inode of tty
- * @filp: file pointer for handle to tty
- *
- * Called the last time each file handle is closed that references
- * this tty. There may however be several such references.
- *
- * Locking:
- * Takes bkl. See tty_release_dev
- *
+/*
* Even releasing the tty structures is a tricky business.. We have
* to be very careful that the structures are all released at the
* same time, as interrupts might otherwise get the wrong pointers.
@@ -1497,20 +1472,20 @@ static void release_tty(struct tty_struct *tty, int idx)
* WSH 09/09/97: rewritten to avoid some nasty race conditions that could
* lead to double frees or releasing memory still in use.
*/
-
-int tty_release(struct inode *inode, struct file *filp)
+void tty_release_dev(struct file *filp)
{
struct tty_struct *tty, *o_tty;
int pty_master, tty_closing, o_tty_closing, do_sleep;
int devpts;
int idx;
char buf[64];
+ struct inode *inode;

+ inode = filp->f_path.dentry->d_inode;
tty = (struct tty_struct *)filp->private_data;
if (tty_paranoia_check(tty, inode, "tty_release_dev"))
- return 0;
+ return;

- lock_kernel();
check_tty_count(tty, "tty_release_dev");

tty_fasync(-1, filp, 0);
@@ -1525,22 +1500,19 @@ int tty_release(struct inode *inode, struct file *filp)
if (idx < 0 || idx >= tty->driver->num) {
printk(KERN_DEBUG "tty_release_dev: bad idx when trying to "
"free (%s)\n", tty->name);
- unlock_kernel();
- return 0;
+ return;
}
if (!devpts) {
if (tty != tty->driver->ttys[idx]) {
- unlock_kernel();
printk(KERN_DEBUG "tty_release_dev: driver.table[%d] not tty "
"for (%s)\n", idx, tty->name);
- return 0;
+ return;
}
if (tty->termios != tty->driver->termios[idx]) {
- unlock_kernel();
printk(KERN_DEBUG "tty_release_dev: driver.termios[%d] not termios "
"for (%s)\n",
idx, tty->name);
- return 0;
+ return;
}
}
#endif
@@ -1554,30 +1526,26 @@ int tty_release(struct inode *inode, struct file *filp)
if (tty->driver->other &&
!(tty->driver->flags & TTY_DRIVER_DEVPTS_MEM)) {
if (o_tty != tty->driver->other->ttys[idx]) {
- unlock_kernel();
printk(KERN_DEBUG "tty_release_dev: other->table[%d] "
"not o_tty for (%s)\n",
idx, tty->name);
- return 0 ;
+ return;
}
if (o_tty->termios != tty->driver->other->termios[idx]) {
- unlock_kernel();
printk(KERN_DEBUG "tty_release_dev: other->termios[%d] "
"not o_termios for (%s)\n",
idx, tty->name);
- return 0;
+ return;
}
if (o_tty->link != tty) {
- unlock_kernel();
printk(KERN_DEBUG "tty_release_dev: bad pty pointers\n");
- return 0;
+ return;
}
}
#endif
if (tty->ops->close)
tty->ops->close(tty, filp);

- unlock_kernel();
/*
* Sanity check: if tty->count is going to zero, there shouldn't be
* any waiters on tty->read_wait or tty->write_wait. We test the
@@ -1600,7 +1568,6 @@ int tty_release(struct inode *inode, struct file *filp)
opens on /dev/tty */

mutex_lock(&tty_mutex);
- lock_kernel();
tty_closing = tty->count <= 1;
o_tty_closing = o_tty &&
(o_tty->count <= (pty_master ? 1 : 0));
@@ -1631,7 +1598,6 @@ int tty_release(struct inode *inode, struct file *filp)

printk(KERN_WARNING "tty_release_dev: %s: read/write wait queue "
"active!\n", tty_name(tty, buf));
- unlock_kernel();
mutex_unlock(&tty_mutex);
schedule();
}
@@ -1695,10 +1661,8 @@ int tty_release(struct inode *inode, struct file *filp)
mutex_unlock(&tty_mutex);

/* check whether both sides are closing ... */
- if (!tty_closing || (o_tty && !o_tty_closing)) {
- unlock_kernel();
- return 0;
- }
+ if (!tty_closing || (o_tty && !o_tty_closing))
+ return;

#ifdef TTY_DEBUG_HANGUP
printk(KERN_DEBUG "freeing tty structure...");
@@ -1716,12 +1680,10 @@ int tty_release(struct inode *inode, struct file *filp)
/* Make this pty number available for reallocation */
if (devpts)
devpts_kill_index(inode, idx);
- unlock_kernel();
- return 0;
}

/**
- * tty_open - open a tty device
+ * __tty_open - open a tty device
* @inode: inode of device file
* @filp: file pointer to tty
*
@@ -1741,7 +1703,7 @@ int tty_release(struct inode *inode, struct file *filp)
* ->siglock protects ->signal/->sighand
*/

-static int tty_open(struct inode *inode, struct file *filp)
+static int __tty_open(struct inode *inode, struct file *filp)
{
struct tty_struct *tty = NULL;
int noctty, retval;
@@ -1758,12 +1720,10 @@ retry_open:
retval = 0;

mutex_lock(&tty_mutex);
- lock_kernel();

if (device == MKDEV(TTYAUX_MAJOR, 0)) {
tty = get_current_tty();
if (!tty) {
- unlock_kernel();
mutex_unlock(&tty_mutex);
return -ENXIO;
}
@@ -1795,14 +1755,12 @@ retry_open:
goto got_driver;
}
}
- unlock_kernel();
mutex_unlock(&tty_mutex);
return -ENODEV;
}

driver = get_tty_driver(device, &index);
if (!driver) {
- unlock_kernel();
mutex_unlock(&tty_mutex);
return -ENODEV;
}
@@ -1812,7 +1770,6 @@ got_driver:
tty = tty_driver_lookup_tty(driver, inode, index);

if (IS_ERR(tty)) {
- unlock_kernel();
mutex_unlock(&tty_mutex);
return PTR_ERR(tty);
}
@@ -1827,10 +1784,8 @@ got_driver:

mutex_unlock(&tty_mutex);
tty_driver_kref_put(driver);
- if (IS_ERR(tty)) {
- unlock_kernel();
+ if (IS_ERR(tty))
return PTR_ERR(tty);
- }

filp->private_data = tty;
file_move(filp, &tty->tty_files);
@@ -1858,15 +1813,11 @@ got_driver:
printk(KERN_DEBUG "error %d in opening %s...", retval,
tty->name);
#endif
- tty_release(inode, filp);
- if (retval != -ERESTARTSYS) {
- unlock_kernel();
+ tty_release_dev(filp);
+ if (retval != -ERESTARTSYS)
return retval;
- }
- if (signal_pending(current)) {
- unlock_kernel();
+ if (signal_pending(current))
return retval;
- }
schedule();
/*
* Need to reset f_op in case a hangup happened.
@@ -1875,11 +1826,8 @@ got_driver:
filp->f_op = &tty_fops;
goto retry_open;
}
- unlock_kernel();
-

mutex_lock(&tty_mutex);
- lock_kernel();
spin_lock_irq(&current->sighand->siglock);
if (!noctty &&
current->signal->leader &&
@@ -1887,13 +1835,44 @@ got_driver:
tty->session == NULL)
__proc_set_tty(current, tty);
spin_unlock_irq(&current->sighand->siglock);
- unlock_kernel();
mutex_unlock(&tty_mutex);
return 0;
}

+/* BKL pushdown: scary code avoidance wrapper */
+static int tty_open(struct inode *inode, struct file *filp)
+{
+ int ret;
+
+ lock_kernel();
+ ret = __tty_open(inode, filp);
+ unlock_kernel();
+ return ret;
+}


+
+
+/**
+ * tty_release - vfs callback for close
+ * @inode: inode of tty
+ * @filp: file pointer for handle to tty
+ *
+ * Called the last time each file handle is closed that references
+ * this tty. There may however be several such references.
+ *
+ * Locking:
+ * Takes bkl. See tty_release_dev
+ */
+
+static int tty_release(struct inode *inode, struct file *filp)
+{
+ lock_kernel();
+ tty_release_dev(filp);
+ unlock_kernel();
+ return 0;
+}
+
/**
* tty_poll - check tty status
* @filp: file being polled
@@ -2338,7 +2317,9 @@ static int tiocsetd(struct tty_struct *tty, int __user *p)
if (get_user(ldisc, p))
return -EFAULT;

+ lock_kernel();
ret = tty_set_ldisc(tty, ldisc);
+ unlock_kernel();

return ret;
}
diff --git a/drivers/char/tty_ldisc.c b/drivers/char/tty_ldisc.c
index d914e77..feb5507 100644
--- a/drivers/char/tty_ldisc.c
+++ b/drivers/char/tty_ldisc.c
@@ -34,8 +34,6 @@
#include <linux/vt_kern.h>
#include <linux/selection.h>

-#include <linux/smp_lock.h> /* For the moment */
-
#include <linux/kmod.h>
#include <linux/nsproxy.h>

@@ -547,7 +545,6 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc)
if (IS_ERR(new_ldisc))
return PTR_ERR(new_ldisc);

- lock_kernel();
/*
* We need to look at the tty locking here for pty/tty pairs
* when both sides try to change in parallel.
@@ -561,7 +558,6 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc)
*/

if (tty->ldisc->ops->num == ldisc) {
- unlock_kernel();
tty_ldisc_put(new_ldisc);
return 0;
}
@@ -573,7 +569,6 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc)

tty_wait_until_sent(tty, 0);

- unlock_kernel();
mutex_lock(&tty->ldisc_mutex);

/*
@@ -587,9 +582,6 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc)
test_bit(TTY_LDISC_CHANGING, &tty->flags) == 0);
mutex_lock(&tty->ldisc_mutex);
}
-
- lock_kernel();
-
set_bit(TTY_LDISC_CHANGING, &tty->flags);

/*
@@ -600,8 +592,6 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc)
tty->receive_room = 0;

o_ldisc = tty->ldisc;
-
- unlock_kernel();
/*
* Make sure we don't change while someone holds a
* reference to the line discipline. The TTY_LDISC bit
@@ -627,14 +617,12 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc)
flush_scheduled_work();

mutex_lock(&tty->ldisc_mutex);
- lock_kernel();
if (test_bit(TTY_HUPPED, &tty->flags)) {
/* We were raced by the hangup method. It will have stomped
the ldisc data and closed the ldisc down */
clear_bit(TTY_LDISC_CHANGING, &tty->flags);
mutex_unlock(&tty->ldisc_mutex);
tty_ldisc_put(new_ldisc);
- unlock_kernel();
return -EIO;
}

@@ -676,7 +664,6 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc)
if (o_work)
schedule_delayed_work(&o_tty->buf.work, 1);
mutex_unlock(&tty->ldisc_mutex);
- unlock_kernel();
return retval;
}

diff --git a/include/linux/tty.h b/include/linux/tty.h
index 405a903..e6da667 100644
--- a/include/linux/tty.h
+++ b/include/linux/tty.h
@@ -449,7 +449,7 @@ extern void initialize_tty_struct(struct tty_struct *tty,
struct tty_driver *driver, int idx);
extern struct tty_struct *tty_init_dev(struct tty_driver *driver, int idx,
int first_ok);
-extern int tty_release(struct inode *inode, struct file *filp);
+extern void tty_release_dev(struct file *filp);
extern int tty_init_termios(struct tty_struct *tty);

extern struct tty_struct *tty_pair_get_tty(struct tty_struct *tty);
From bd9a619494c123470a081e5e30602c307de2bba3 Mon Sep 17 00:00:00 2001
From: Ingo Molnar <mingo@elte.hu>
Date: Sat, 12 Dec 2009 11:07:55 +0100
Subject: [PATCH] Revert "tty: Push the lock down further into the ldisc code"

This reverts commit f18f9498e90327b9b0e245e191029e6e1996d203.

diff --git a/drivers/char/tty_io.c b/drivers/char/tty_io.c
index c408c81..1e24130 100644
--- a/drivers/char/tty_io.c
+++ b/drivers/char/tty_io.c
@@ -1347,7 +1347,9 @@ struct tty_struct *tty_init_dev(struct tty_driver *driver, int idx,
* If we fail here just call release_tty to clean up. No need
* to decrement the use counts, as release_tty doesn't care.
*/
+ lock_kernel();
retval = tty_ldisc_setup(tty, tty->link);
+ unlock_kernel();
if (retval)
goto release_mem_out;
return tty;
diff --git a/drivers/char/tty_ldisc.c b/drivers/char/tty_ldisc.c
index 3f653f7..d914e77 100644
--- a/drivers/char/tty_ldisc.c
+++ b/drivers/char/tty_ldisc.c
@@ -445,14 +445,8 @@ static void tty_set_termios_ldisc(struct tty_struct *tty, int num)
static int tty_ldisc_open(struct tty_struct *tty, struct tty_ldisc *ld)
{
WARN_ON(test_and_set_bit(TTY_LDISC_OPEN, &tty->flags));
- if (ld->ops->open) {
- int ret;
- /* BKL here locks verus a hangup event */
- lock_kernel();
- ret = ld->ops->open(tty);
- unlock_kernel();
- return ret;
- }
+ if (ld->ops->open)
+ return ld->ops->open(tty);
return 0;
}

@@ -572,7 +566,6 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc)
return 0;
}

- unlock_kernel();
/*
* Problem: What do we do if this blocks ?
* We could deadlock here
@@ -580,6 +573,7 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc)

tty_wait_until_sent(tty, 0);

+ unlock_kernel();
mutex_lock(&tty->ldisc_mutex);

/*
From 8e991a5112643a63820a1088860f0c7c869d6f25 Mon Sep 17 00:00:00 2001
From: Ingo Molnar <mingo@elte.hu>
Date: Sat, 12 Dec 2009 11:07:46 +0100
Subject: [PATCH] Revert "tty: Push the bkl down a bit in the hangup code"

This reverts commit 38c70b27f9502c31c1d0c29676275f7362cdb0d9.

diff --git a/drivers/char/tty_io.c b/drivers/char/tty_io.c
index cc941a3..c408c81 100644
--- a/drivers/char/tty_io.c
+++ b/drivers/char/tty_io.c
@@ -505,6 +505,8 @@ static void do_tty_hangup(struct work_struct *work)
if (!tty)
return;

+ /* inuse_filps is protected by the single kernel lock */
+ lock_kernel();

spin_lock(&redirect_lock);
if (redirect && redirect->private_data == tty) {
@@ -513,8 +515,6 @@ static void do_tty_hangup(struct work_struct *work)
}
spin_unlock(&redirect_lock);

- /* inuse_filps is protected by the single kernel lock */
- lock_kernel();
check_tty_count(tty, "do_tty_hangup");
file_list_lock();
/* This breaks for file handles being sent over AF_UNIX sockets ? */
From 9d6d77b3c56e6c169e50b6bb9033e4a2e7d4ec71 Mon Sep 17 00:00:00 2001
From: Ingo Molnar <mingo@elte.hu>
Date: Sat, 12 Dec 2009 11:07:38 +0100
Subject: [PATCH] Revert "tty: Move the leader test in disassociate"

This reverts commit 5ec93d1154fd1e269162398f8e70efc7e004485d.

diff --git a/drivers/char/tty_io.c b/drivers/char/tty_io.c
index a19fef2..cc941a3 100644
--- a/drivers/char/tty_io.c
+++ b/drivers/char/tty_io.c
@@ -707,8 +707,6 @@ void disassociate_ctty(int on_exit)
struct tty_struct *tty;
struct pid *tty_pgrp = NULL;

- if (!current->signal->leader)
- return;

tty = get_current_tty();
if (tty) {
@@ -774,7 +772,8 @@ void no_tty(void)
{
struct task_struct *tsk = current;
lock_kernel();
- disassociate_ctty(0);
+ if (tsk->signal->leader)
+ disassociate_ctty(0);
unlock_kernel();
proc_clear_tty(tsk);
}
diff --git a/kernel/exit.c b/kernel/exit.c
index 6f50ef5..1143012 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -971,7 +971,7 @@ NORET_TYPE void do_exit(long code)
exit_thread();
cgroup_exit(tsk, 1);

- if (group_dead)
+ if (group_dead && tsk->signal->leader)
disassociate_ctty(1);

module_put(task_thread_info(tsk)->exec_domain->module);
From 153d2afe47cc994d35adc7e61be13bf840fd0b47 Mon Sep 17 00:00:00 2001
From: Ingo Molnar <mingo@elte.hu>
Date: Sat, 12 Dec 2009 11:07:28 +0100
Subject: [PATCH] Revert "tty: split the lock up a bit further"

This reverts commit 36ba782e9674cdc29ec7003757df0b375e99fa96.

diff --git a/drivers/char/tty_io.c b/drivers/char/tty_io.c
index 684f0e0..a19fef2 100644
--- a/drivers/char/tty_io.c
+++ b/drivers/char/tty_io.c
@@ -516,8 +516,6 @@ static void do_tty_hangup(struct work_struct *work)
/* inuse_filps is protected by the single kernel lock */
lock_kernel();
check_tty_count(tty, "do_tty_hangup");
- unlock_kernel();
-
file_list_lock();
/* This breaks for file handles being sent over AF_UNIX sockets ? */
list_for_each_entry(filp, &tty->tty_files, f_u.fu_list) {
@@ -531,7 +529,6 @@ static void do_tty_hangup(struct work_struct *work)
}
file_list_unlock();

- lock_kernel();
tty_ldisc_hangup(tty);

read_lock(&tasklist_lock);


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