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tty: n_hdlc: use guard()s

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Use guards in the n_hdlc code. This improves readability, makes error
handling easier, and marks locked portions of code explicit. All that
while being sure the lock is unlocked.

Signed-off-by: Jiri Slaby (SUSE) <jirislaby@kernel.org>
Link: https://patch.msgid.link/20251119100140.830761-5-jirislaby@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Jiri Slaby (SUSE)
2025-11-19 11:01:34 +01:00
committed by Greg Kroah-Hartman
parent 3ae99599bf
commit 8c03bfcf6b
1 changed files with 26 additions and 41 deletions
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67
drivers/tty/n_hdlc.c
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@@ -263,21 +263,18 @@ static int n_hdlc_tty_open(struct tty_struct *tty)
*/
static void n_hdlc_send_frames(struct n_hdlc *n_hdlc, struct tty_struct *tty)
{
unsigned long flags;
struct n_hdlc_buf *tbuf;
ssize_t actual;
check_again:
spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock, flags);
if (n_hdlc->tbusy) {
n_hdlc->woke_up = true;
spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);
return;
scoped_guard(spinlock_irqsave, &n_hdlc->tx_buf_list.spinlock) {
if (n_hdlc->tbusy) {
n_hdlc->woke_up = true;
return;
}
n_hdlc->tbusy = true;
n_hdlc->woke_up = false;
}
n_hdlc->tbusy = true;
n_hdlc->woke_up = false;
spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);
tbuf = n_hdlc_buf_get(&n_hdlc->tx_buf_list);
while (tbuf) {
@@ -324,9 +321,8 @@ static void n_hdlc_send_frames(struct n_hdlc *n_hdlc, struct tty_struct *tty)
clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
/* Clear the re-entry flag */
spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock, flags);
n_hdlc->tbusy = false;
spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);
scoped_guard(spinlock_irqsave, &n_hdlc->tx_buf_list.spinlock)
n_hdlc->tbusy = false;
if (n_hdlc->woke_up)
goto check_again;
@@ -585,7 +581,6 @@ static int n_hdlc_tty_ioctl(struct tty_struct *tty, unsigned int cmd,
{
struct n_hdlc *n_hdlc = tty->disc_data;
int count;
unsigned long flags;
struct n_hdlc_buf *buf = NULL;
pr_debug("%s() called %d\n", __func__, cmd);
@@ -594,26 +589,26 @@ static int n_hdlc_tty_ioctl(struct tty_struct *tty, unsigned int cmd,
case FIONREAD:
/* report count of read data available */
/* in next available frame (if any) */
spin_lock_irqsave(&n_hdlc->rx_buf_list.spinlock, flags);
buf = list_first_entry_or_null(&n_hdlc->rx_buf_list.list,
struct n_hdlc_buf, list_item);
if (buf)
count = buf->count;
else
count = 0;
spin_unlock_irqrestore(&n_hdlc->rx_buf_list.spinlock, flags);
scoped_guard(spinlock_irqsave, &n_hdlc->rx_buf_list.spinlock) {
buf = list_first_entry_or_null(&n_hdlc->rx_buf_list.list,
struct n_hdlc_buf, list_item);
if (buf)
count = buf->count;
else
count = 0;
}
return put_user(count, (int __user *)arg);
case TIOCOUTQ:
/* get the pending tx byte count in the driver */
count = tty_chars_in_buffer(tty);
/* add size of next output frame in queue */
spin_lock_irqsave(&n_hdlc->tx_buf_list.spinlock, flags);
buf = list_first_entry_or_null(&n_hdlc->tx_buf_list.list,
struct n_hdlc_buf, list_item);
if (buf)
count += buf->count;
spin_unlock_irqrestore(&n_hdlc->tx_buf_list.spinlock, flags);
scoped_guard(spinlock_irqsave, &n_hdlc->tx_buf_list.spinlock) {
buf = list_first_entry_or_null(&n_hdlc->tx_buf_list.list,
struct n_hdlc_buf, list_item);
if (buf)
count += buf->count;
}
return put_user(count, (int __user *)arg);
case TCFLSH:
@@ -720,14 +715,10 @@ static struct n_hdlc *n_hdlc_alloc(void)
static void n_hdlc_buf_return(struct n_hdlc_buf_list *buf_list,
struct n_hdlc_buf *buf)
{
unsigned long flags;
spin_lock_irqsave(&buf_list->spinlock, flags);
guard(spinlock_irqsave)(&buf_list->spinlock);
list_add(&buf->list_item, &buf_list->list);
buf_list->count++;
spin_unlock_irqrestore(&buf_list->spinlock, flags);
}
/**
@@ -738,14 +729,10 @@ static void n_hdlc_buf_return(struct n_hdlc_buf_list *buf_list,
static void n_hdlc_buf_put(struct n_hdlc_buf_list *buf_list,
struct n_hdlc_buf *buf)
{
unsigned long flags;
spin_lock_irqsave(&buf_list->spinlock, flags);
guard(spinlock_irqsave)(&buf_list->spinlock);
list_add_tail(&buf->list_item, &buf_list->list);
buf_list->count++;
spin_unlock_irqrestore(&buf_list->spinlock, flags);
} /* end of n_hdlc_buf_put() */
/**
@@ -758,10 +745,9 @@ static void n_hdlc_buf_put(struct n_hdlc_buf_list *buf_list,
*/
static struct n_hdlc_buf *n_hdlc_buf_get(struct n_hdlc_buf_list *buf_list)
{
unsigned long flags;
struct n_hdlc_buf *buf;
spin_lock_irqsave(&buf_list->spinlock, flags);
guard(spinlock_irqsave)(&buf_list->spinlock);
buf = list_first_entry_or_null(&buf_list->list,
struct n_hdlc_buf, list_item);
@@ -770,7 +756,6 @@ static struct n_hdlc_buf *n_hdlc_buf_get(struct n_hdlc_buf_list *buf_list)
buf_list->count--;
}
spin_unlock_irqrestore(&buf_list->spinlock, flags);
return buf;
} /* end of n_hdlc_buf_get() */