Merge git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty-2.6
* git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty-2.6: tty-ldisc: be more careful in 'put_ldisc' locking tty-ldisc: turn ldisc user count into a proper refcount tty-ldisc: make refcount be atomic_t 'users' count
This commit is contained in:
commit
9f3eea6a2f
|
@ -48,6 +48,41 @@ static DECLARE_WAIT_QUEUE_HEAD(tty_ldisc_wait);
|
|||
/* Line disc dispatch table */
|
||||
static struct tty_ldisc_ops *tty_ldiscs[NR_LDISCS];
|
||||
|
||||
static inline struct tty_ldisc *get_ldisc(struct tty_ldisc *ld)
|
||||
{
|
||||
if (ld)
|
||||
atomic_inc(&ld->users);
|
||||
return ld;
|
||||
}
|
||||
|
||||
static void put_ldisc(struct tty_ldisc *ld)
|
||||
{
|
||||
unsigned long flags;
|
||||
|
||||
if (WARN_ON_ONCE(!ld))
|
||||
return;
|
||||
|
||||
/*
|
||||
* If this is the last user, free the ldisc, and
|
||||
* release the ldisc ops.
|
||||
*
|
||||
* We really want an "atomic_dec_and_lock_irqsave()",
|
||||
* but we don't have it, so this does it by hand.
|
||||
*/
|
||||
local_irq_save(flags);
|
||||
if (atomic_dec_and_lock(&ld->users, &tty_ldisc_lock)) {
|
||||
struct tty_ldisc_ops *ldo = ld->ops;
|
||||
|
||||
ldo->refcount--;
|
||||
module_put(ldo->owner);
|
||||
spin_unlock_irqrestore(&tty_ldisc_lock, flags);
|
||||
|
||||
kfree(ld);
|
||||
return;
|
||||
}
|
||||
local_irq_restore(flags);
|
||||
}
|
||||
|
||||
/**
|
||||
* tty_register_ldisc - install a line discipline
|
||||
* @disc: ldisc number
|
||||
|
@ -142,7 +177,7 @@ static struct tty_ldisc *tty_ldisc_try_get(int disc)
|
|||
/* lock it */
|
||||
ldops->refcount++;
|
||||
ld->ops = ldops;
|
||||
ld->refcount = 0;
|
||||
atomic_set(&ld->users, 1);
|
||||
err = 0;
|
||||
}
|
||||
}
|
||||
|
@ -181,35 +216,6 @@ static struct tty_ldisc *tty_ldisc_get(int disc)
|
|||
return ld;
|
||||
}
|
||||
|
||||
/**
|
||||
* tty_ldisc_put - drop ldisc reference
|
||||
* @ld: ldisc
|
||||
*
|
||||
* Drop a reference to a line discipline. Manage refcounts and
|
||||
* module usage counts. Free the ldisc once the recount hits zero.
|
||||
*
|
||||
* Locking:
|
||||
* takes tty_ldisc_lock to guard against ldisc races
|
||||
*/
|
||||
|
||||
static void tty_ldisc_put(struct tty_ldisc *ld)
|
||||
{
|
||||
unsigned long flags;
|
||||
int disc = ld->ops->num;
|
||||
struct tty_ldisc_ops *ldo;
|
||||
|
||||
BUG_ON(disc < N_TTY || disc >= NR_LDISCS);
|
||||
|
||||
spin_lock_irqsave(&tty_ldisc_lock, flags);
|
||||
ldo = tty_ldiscs[disc];
|
||||
BUG_ON(ldo->refcount == 0);
|
||||
ldo->refcount--;
|
||||
module_put(ldo->owner);
|
||||
spin_unlock_irqrestore(&tty_ldisc_lock, flags);
|
||||
WARN_ON(ld->refcount);
|
||||
kfree(ld);
|
||||
}
|
||||
|
||||
static void *tty_ldiscs_seq_start(struct seq_file *m, loff_t *pos)
|
||||
{
|
||||
return (*pos < NR_LDISCS) ? pos : NULL;
|
||||
|
@ -234,7 +240,7 @@ static int tty_ldiscs_seq_show(struct seq_file *m, void *v)
|
|||
if (IS_ERR(ld))
|
||||
return 0;
|
||||
seq_printf(m, "%-10s %2d\n", ld->ops->name ? ld->ops->name : "???", i);
|
||||
tty_ldisc_put(ld);
|
||||
put_ldisc(ld);
|
||||
return 0;
|
||||
}
|
||||
|
||||
|
@ -288,20 +294,17 @@ static void tty_ldisc_assign(struct tty_struct *tty, struct tty_ldisc *ld)
|
|||
* Locking: takes tty_ldisc_lock
|
||||
*/
|
||||
|
||||
static int tty_ldisc_try(struct tty_struct *tty)
|
||||
static struct tty_ldisc *tty_ldisc_try(struct tty_struct *tty)
|
||||
{
|
||||
unsigned long flags;
|
||||
struct tty_ldisc *ld;
|
||||
int ret = 0;
|
||||
|
||||
spin_lock_irqsave(&tty_ldisc_lock, flags);
|
||||
ld = tty->ldisc;
|
||||
if (test_bit(TTY_LDISC, &tty->flags)) {
|
||||
ld->refcount++;
|
||||
ret = 1;
|
||||
}
|
||||
ld = NULL;
|
||||
if (test_bit(TTY_LDISC, &tty->flags))
|
||||
ld = get_ldisc(tty->ldisc);
|
||||
spin_unlock_irqrestore(&tty_ldisc_lock, flags);
|
||||
return ret;
|
||||
return ld;
|
||||
}
|
||||
|
||||
/**
|
||||
|
@ -322,10 +325,11 @@ static int tty_ldisc_try(struct tty_struct *tty)
|
|||
|
||||
struct tty_ldisc *tty_ldisc_ref_wait(struct tty_struct *tty)
|
||||
{
|
||||
struct tty_ldisc *ld;
|
||||
|
||||
/* wait_event is a macro */
|
||||
wait_event(tty_ldisc_wait, tty_ldisc_try(tty));
|
||||
WARN_ON(tty->ldisc->refcount == 0);
|
||||
return tty->ldisc;
|
||||
wait_event(tty_ldisc_wait, (ld = tty_ldisc_try(tty)) != NULL);
|
||||
return ld;
|
||||
}
|
||||
EXPORT_SYMBOL_GPL(tty_ldisc_ref_wait);
|
||||
|
||||
|
@ -342,9 +346,7 @@ EXPORT_SYMBOL_GPL(tty_ldisc_ref_wait);
|
|||
|
||||
struct tty_ldisc *tty_ldisc_ref(struct tty_struct *tty)
|
||||
{
|
||||
if (tty_ldisc_try(tty))
|
||||
return tty->ldisc;
|
||||
return NULL;
|
||||
return tty_ldisc_try(tty);
|
||||
}
|
||||
EXPORT_SYMBOL_GPL(tty_ldisc_ref);
|
||||
|
||||
|
@ -360,21 +362,15 @@ EXPORT_SYMBOL_GPL(tty_ldisc_ref);
|
|||
|
||||
void tty_ldisc_deref(struct tty_ldisc *ld)
|
||||
{
|
||||
unsigned long flags;
|
||||
|
||||
BUG_ON(ld == NULL);
|
||||
|
||||
spin_lock_irqsave(&tty_ldisc_lock, flags);
|
||||
if (ld->refcount == 0)
|
||||
printk(KERN_ERR "tty_ldisc_deref: no references.\n");
|
||||
else
|
||||
ld->refcount--;
|
||||
if (ld->refcount == 0)
|
||||
wake_up(&tty_ldisc_wait);
|
||||
spin_unlock_irqrestore(&tty_ldisc_lock, flags);
|
||||
put_ldisc(ld);
|
||||
}
|
||||
EXPORT_SYMBOL_GPL(tty_ldisc_deref);
|
||||
|
||||
static inline void tty_ldisc_put(struct tty_ldisc *ld)
|
||||
{
|
||||
put_ldisc(ld);
|
||||
}
|
||||
|
||||
/**
|
||||
* tty_ldisc_enable - allow ldisc use
|
||||
* @tty: terminal to activate ldisc on
|
||||
|
@ -522,31 +518,6 @@ static int tty_ldisc_halt(struct tty_struct *tty)
|
|||
return cancel_delayed_work(&tty->buf.work);
|
||||
}
|
||||
|
||||
/**
|
||||
* tty_ldisc_wait_idle - wait for the ldisc to become idle
|
||||
* @tty: tty to wait for
|
||||
*
|
||||
* Wait for the line discipline to become idle. The discipline must
|
||||
* have been halted for this to guarantee it remains idle.
|
||||
*
|
||||
* tty_ldisc_lock protects the ref counts currently.
|
||||
*/
|
||||
|
||||
static int tty_ldisc_wait_idle(struct tty_struct *tty)
|
||||
{
|
||||
unsigned long flags;
|
||||
spin_lock_irqsave(&tty_ldisc_lock, flags);
|
||||
while (tty->ldisc->refcount) {
|
||||
spin_unlock_irqrestore(&tty_ldisc_lock, flags);
|
||||
if (wait_event_timeout(tty_ldisc_wait,
|
||||
tty->ldisc->refcount == 0, 5 * HZ) == 0)
|
||||
return -EBUSY;
|
||||
spin_lock_irqsave(&tty_ldisc_lock, flags);
|
||||
}
|
||||
spin_unlock_irqrestore(&tty_ldisc_lock, flags);
|
||||
return 0;
|
||||
}
|
||||
|
||||
/**
|
||||
* tty_set_ldisc - set line discipline
|
||||
* @tty: the terminal to set
|
||||
|
@ -642,14 +613,6 @@ int tty_set_ldisc(struct tty_struct *tty, int ldisc)
|
|||
|
||||
flush_scheduled_work();
|
||||
|
||||
/* Let any existing reference holders finish */
|
||||
retval = tty_ldisc_wait_idle(tty);
|
||||
if (retval < 0) {
|
||||
clear_bit(TTY_LDISC_CHANGING, &tty->flags);
|
||||
tty_ldisc_put(new_ldisc);
|
||||
return retval;
|
||||
}
|
||||
|
||||
mutex_lock(&tty->ldisc_mutex);
|
||||
if (test_bit(TTY_HUPPED, &tty->flags)) {
|
||||
/* We were raced by the hangup method. It will have stomped
|
||||
|
@ -795,7 +758,6 @@ void tty_ldisc_hangup(struct tty_struct *tty)
|
|||
if (tty->ldisc) { /* Not yet closed */
|
||||
/* Switch back to N_TTY */
|
||||
tty_ldisc_halt(tty);
|
||||
tty_ldisc_wait_idle(tty);
|
||||
tty_ldisc_reinit(tty);
|
||||
/* At this point we have a closed ldisc and we want to
|
||||
reopen it. We could defer this to the next open but
|
||||
|
@ -860,14 +822,6 @@ void tty_ldisc_release(struct tty_struct *tty, struct tty_struct *o_tty)
|
|||
tty_ldisc_halt(tty);
|
||||
flush_scheduled_work();
|
||||
|
||||
/*
|
||||
* Wait for any short term users (we know they are just driver
|
||||
* side waiters as the file is closing so user count on the file
|
||||
* side is zero.
|
||||
*/
|
||||
|
||||
tty_ldisc_wait_idle(tty);
|
||||
|
||||
mutex_lock(&tty->ldisc_mutex);
|
||||
/*
|
||||
* Now kill off the ldisc
|
||||
|
|
|
@ -144,7 +144,7 @@ struct tty_ldisc_ops {
|
|||
|
||||
struct tty_ldisc {
|
||||
struct tty_ldisc_ops *ops;
|
||||
int refcount;
|
||||
atomic_t users;
|
||||
};
|
||||
|
||||
#define TTY_LDISC_MAGIC 0x5403
|
||||
|
|
Loading…
Reference in a new issue