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Subject[PATCH 67/69] TTY: rfcomm/tty, use tty_port refcounting
Date
Switch the refcounting from manual atomic plays with refcounter to the
one offered by tty_port.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
net/bluetooth/rfcomm/tty.c | 58 ++++++++++++++++++++------------------------
1 file changed, 26 insertions(+), 32 deletions(-)

diff --git a/net/bluetooth/rfcomm/tty.c b/net/bluetooth/rfcomm/tty.c
index 97c2a08..da4f545 100644
--- a/net/bluetooth/rfcomm/tty.c
+++ b/net/bluetooth/rfcomm/tty.c
@@ -50,7 +50,6 @@ static struct tty_driver *rfcomm_tty_driver;
struct rfcomm_dev {
struct tty_port port;
struct list_head list;
- atomic_t refcnt;

char name[12];
int id;
@@ -85,8 +84,17 @@ static void rfcomm_dev_modem_status(struct rfcomm_dlc *dlc, u8 v24_sig);
static void rfcomm_tty_wakeup(struct work_struct *work);

/* ---- Device functions ---- */
-static void rfcomm_dev_destruct(struct rfcomm_dev *dev)
+
+/*
+ * The reason this isn't actually a race, as you no doubt have a little voice
+ * screaming at you in your head, is that the refcount should never actually
+ * reach zero unless the device has already been taken off the list, in
+ * rfcomm_dev_del(). And if that's not true, we'll hit the BUG() in
+ * rfcomm_dev_destruct() anyway.
+ */
+static void rfcomm_dev_destruct(struct tty_port *port)
{
+ struct rfcomm_dev *dev = container_of(port, struct rfcomm_dev, port);
struct rfcomm_dlc *dlc = dev->dlc;

BT_DBG("dev %p dlc %p", dev, dlc);
@@ -113,23 +121,9 @@ static void rfcomm_dev_destruct(struct rfcomm_dev *dev)
module_put(THIS_MODULE);
}

-static inline void rfcomm_dev_hold(struct rfcomm_dev *dev)
-{
- atomic_inc(&dev->refcnt);
-}
-
-static inline void rfcomm_dev_put(struct rfcomm_dev *dev)
-{
- /* The reason this isn't actually a race, as you no
- doubt have a little voice screaming at you in your
- head, is that the refcount should never actually
- reach zero unless the device has already been taken
- off the list, in rfcomm_dev_del(). And if that's not
- true, we'll hit the BUG() in rfcomm_dev_destruct()
- anyway. */
- if (atomic_dec_and_test(&dev->refcnt))
- rfcomm_dev_destruct(dev);
-}
+static const struct tty_port_operations rfcomm_port_ops = {
+ .destruct = rfcomm_dev_destruct,
+};

static struct rfcomm_dev *__rfcomm_dev_get(int id)
{
@@ -154,7 +148,7 @@ static inline struct rfcomm_dev *rfcomm_dev_get(int id)
if (test_bit(RFCOMM_TTY_RELEASED, &dev->flags))
dev = NULL;
else
- rfcomm_dev_hold(dev);
+ tty_port_get(&dev->port);
}

spin_unlock(&rfcomm_dev_lock);
@@ -241,7 +235,6 @@ static int rfcomm_dev_add(struct rfcomm_dev_req *req, struct rfcomm_dlc *dlc)
sprintf(dev->name, "rfcomm%d", dev->id);

list_add(&dev->list, head);
- atomic_set(&dev->refcnt, 1);

bacpy(&dev->src, &req->src);
bacpy(&dev->dst, &req->dst);
@@ -253,6 +246,7 @@ static int rfcomm_dev_add(struct rfcomm_dev_req *req, struct rfcomm_dlc *dlc)
atomic_set(&dev->opened, 0);

tty_port_init(&dev->port);
+ dev->port.ops = &rfcomm_port_ops;
init_waitqueue_head(&dev->wait);
INIT_WORK(&dev->wakeup_task, rfcomm_tty_wakeup);

@@ -332,7 +326,7 @@ static void rfcomm_dev_del(struct rfcomm_dev *dev)
list_del_init(&dev->list);
spin_unlock(&rfcomm_dev_lock);

- rfcomm_dev_put(dev);
+ tty_port_put(&dev->port);
}

/* ---- Send buffer ---- */
@@ -349,12 +343,12 @@ static void rfcomm_wfree(struct sk_buff *skb)
atomic_sub(skb->truesize, &dev->wmem_alloc);
if (test_bit(RFCOMM_TTY_ATTACHED, &dev->flags))
queue_work(system_nrt_wq, &dev->wakeup_task);
- rfcomm_dev_put(dev);
+ tty_port_put(&dev->port);
}

static inline void rfcomm_set_owner_w(struct sk_buff *skb, struct rfcomm_dev *dev)
{
- rfcomm_dev_hold(dev);
+ tty_port_get(&dev->port);
atomic_add(skb->truesize, &dev->wmem_alloc);
skb->sk = (void *) dev;
skb->destructor = rfcomm_wfree;
@@ -433,7 +427,7 @@ static int rfcomm_release_dev(void __user *arg)
return -ENODEV;

if (dev->flags != NOCAP_FLAGS && !capable(CAP_NET_ADMIN)) {
- rfcomm_dev_put(dev);
+ tty_port_put(&dev->port);
return -EPERM;
}

@@ -446,7 +440,7 @@ static int rfcomm_release_dev(void __user *arg)

if (!test_bit(RFCOMM_RELEASE_ONHUP, &dev->flags))
rfcomm_dev_del(dev);
- rfcomm_dev_put(dev);
+ tty_port_put(&dev->port);
return 0;
}

@@ -524,7 +518,7 @@ static int rfcomm_get_dev_info(void __user *arg)
if (copy_to_user(arg, &di, sizeof(di)))
err = -EFAULT;

- rfcomm_dev_put(dev);
+ tty_port_put(&dev->port);
return err;
}

@@ -592,7 +586,7 @@ static void rfcomm_dev_state_change(struct rfcomm_dlc *dlc, int err)
* 1. rfcomm_dev_get will take rfcomm_dev_lock
* but in rfcomm_dev_add there's lock order:
* rfcomm_dev_lock -> dlc lock
- * 2. rfcomm_dev_put will deadlock if it's
+ * 2. tty_port_put will deadlock if it's
* the last reference
*/
rfcomm_dlc_unlock(dlc);
@@ -602,7 +596,7 @@ static void rfcomm_dev_state_change(struct rfcomm_dlc *dlc, int err)
}

rfcomm_dev_del(dev);
- rfcomm_dev_put(dev);
+ tty_port_put(&dev->port);
rfcomm_dlc_lock(dlc);
}
} else
@@ -771,11 +765,11 @@ static void rfcomm_tty_close(struct tty_struct *tty, struct file *filp)
list_del_init(&dev->list);
spin_unlock(&rfcomm_dev_lock);

- rfcomm_dev_put(dev);
+ tty_port_put(&dev->port);
}
}

- rfcomm_dev_put(dev);
+ tty_port_put(&dev->port);
}

static int rfcomm_tty_write(struct tty_struct *tty, const unsigned char *buf, int count)
@@ -1084,7 +1078,7 @@ static void rfcomm_tty_hangup(struct tty_struct *tty)
if (rfcomm_dev_get(dev->id) == NULL)
return;
rfcomm_dev_del(dev);
- rfcomm_dev_put(dev);
+ tty_port_put(&dev->port);
}
}

--
1.7.9.2



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