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Message-ID: <20251119100140.830761-3-jirislaby@kernel.org>
Date: Wed, 19 Nov 2025 11:01:32 +0100
From: "Jiri Slaby (SUSE)" <jirislaby@...nel.org>
To: gregkh@...uxfoundation.org
Cc: linux-serial@...r.kernel.org,
linux-kernel@...r.kernel.org,
"Jiri Slaby (SUSE)" <jirislaby@...nel.org>
Subject: [PATCH 02/10] tty: n_tty: use guard()s
Use guards in the n_tty 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@...nel.org>
---
drivers/tty/n_tty.c | 109 +++++++++++++++++++-------------------------
1 file changed, 48 insertions(+), 61 deletions(-)
diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c
index 6af3f3a0b531..e6a0f5b40d0a 100644
--- a/drivers/tty/n_tty.c
+++ b/drivers/tty/n_tty.c
@@ -324,12 +324,9 @@ static void reset_buffer_flags(struct n_tty_data *ldata)
static void n_tty_packet_mode_flush(struct tty_struct *tty)
{
- unsigned long flags;
-
if (tty->link->ctrl.packet) {
- spin_lock_irqsave(&tty->ctrl.lock, flags);
- tty->ctrl.pktstatus |= TIOCPKT_FLUSHREAD;
- spin_unlock_irqrestore(&tty->ctrl.lock, flags);
+ scoped_guard(spinlock_irqsave, &tty->ctrl.lock)
+ tty->ctrl.pktstatus |= TIOCPKT_FLUSHREAD;
wake_up_interruptible(&tty->link->read_wait);
}
}
@@ -349,13 +346,12 @@ static void n_tty_packet_mode_flush(struct tty_struct *tty)
*/
static void n_tty_flush_buffer(struct tty_struct *tty)
{
- down_write(&tty->termios_rwsem);
+ guard(rwsem_write)(&tty->termios_rwsem);
reset_buffer_flags(tty->disc_data);
n_tty_kick_worker(tty);
if (tty->link)
n_tty_packet_mode_flush(tty);
- up_write(&tty->termios_rwsem);
}
/**
@@ -737,24 +733,22 @@ static void commit_echoes(struct tty_struct *tty)
size_t nr, old, echoed;
size_t head;
- mutex_lock(&ldata->output_lock);
- head = ldata->echo_head;
- ldata->echo_mark = head;
- old = ldata->echo_commit - ldata->echo_tail;
-
- /* Process committed echoes if the accumulated # of bytes
- * is over the threshold (and try again each time another
- * block is accumulated) */
- nr = head - ldata->echo_tail;
- if (nr < ECHO_COMMIT_WATERMARK ||
- (nr % ECHO_BLOCK > old % ECHO_BLOCK)) {
- mutex_unlock(&ldata->output_lock);
- return;
- }
+ scoped_guard(mutex, &ldata->output_lock) {
+ head = ldata->echo_head;
+ ldata->echo_mark = head;
+ old = ldata->echo_commit - ldata->echo_tail;
+
+ /*
+ * Process committed echoes if the accumulated # of bytes is over the threshold
+ * (and try again each time another block is accumulated)
+ */
+ nr = head - ldata->echo_tail;
+ if (nr < ECHO_COMMIT_WATERMARK || (nr % ECHO_BLOCK > old % ECHO_BLOCK))
+ return;
- ldata->echo_commit = head;
- echoed = __process_echoes(tty);
- mutex_unlock(&ldata->output_lock);
+ ldata->echo_commit = head;
+ echoed = __process_echoes(tty);
+ }
if (echoed && tty->ops->flush_chars)
tty->ops->flush_chars(tty);
@@ -768,10 +762,10 @@ static void process_echoes(struct tty_struct *tty)
if (ldata->echo_mark == ldata->echo_tail)
return;
- mutex_lock(&ldata->output_lock);
- ldata->echo_commit = ldata->echo_mark;
- echoed = __process_echoes(tty);
- mutex_unlock(&ldata->output_lock);
+ scoped_guard(mutex, &ldata->output_lock) {
+ ldata->echo_commit = ldata->echo_mark;
+ echoed = __process_echoes(tty);
+ }
if (echoed && tty->ops->flush_chars)
tty->ops->flush_chars(tty);
@@ -786,10 +780,9 @@ static void flush_echoes(struct tty_struct *tty)
ldata->echo_commit == ldata->echo_head)
return;
- mutex_lock(&ldata->output_lock);
+ guard(mutex)(&ldata->output_lock);
ldata->echo_commit = ldata->echo_head;
__process_echoes(tty);
- mutex_unlock(&ldata->output_lock);
}
/**
@@ -1078,18 +1071,19 @@ static void isig(int sig, struct tty_struct *tty)
if (L_NOFLSH(tty)) {
/* signal only */
__isig(sig, tty);
+ return;
+ }
- } else { /* signal and flush */
- up_read(&tty->termios_rwsem);
- down_write(&tty->termios_rwsem);
-
+ /* signal and flush */
+ up_read(&tty->termios_rwsem);
+ scoped_guard(rwsem_write, &tty->termios_rwsem) {
__isig(sig, tty);
/* clear echo buffer */
- mutex_lock(&ldata->output_lock);
- ldata->echo_head = ldata->echo_tail = 0;
- ldata->echo_mark = ldata->echo_commit = 0;
- mutex_unlock(&ldata->output_lock);
+ scoped_guard(mutex, &ldata->output_lock) {
+ ldata->echo_head = ldata->echo_tail = 0;
+ ldata->echo_mark = ldata->echo_commit = 0;
+ }
/* clear output buffer */
tty_driver_flush_buffer(tty);
@@ -1100,10 +1094,8 @@ static void isig(int sig, struct tty_struct *tty)
/* notify pty master of flush */
if (tty->link)
n_tty_packet_mode_flush(tty);
-
- up_write(&tty->termios_rwsem);
- down_read(&tty->termios_rwsem);
}
+ down_read(&tty->termios_rwsem);
}
/**
@@ -1683,7 +1675,7 @@ n_tty_receive_buf_common(struct tty_struct *tty, const u8 *cp, const u8 *fp,
size_t n, rcvd = 0;
int room, overflow;
- down_read(&tty->termios_rwsem);
+ guard(rwsem_read)(&tty->termios_rwsem);
do {
/*
@@ -1752,8 +1744,6 @@ n_tty_receive_buf_common(struct tty_struct *tty, const u8 *cp, const u8 *fp,
n_tty_kick_worker(tty);
}
- up_read(&tty->termios_rwsem);
-
return rcvd;
}
@@ -1879,10 +1869,9 @@ static void n_tty_close(struct tty_struct *tty)
if (tty->link)
n_tty_packet_mode_flush(tty);
- down_write(&tty->termios_rwsem);
+ guard(rwsem_write)(&tty->termios_rwsem);
vfree(ldata);
tty->disc_data = NULL;
- up_write(&tty->termios_rwsem);
}
/**
@@ -2247,10 +2236,10 @@ static ssize_t n_tty_read(struct tty_struct *tty, struct file *file, u8 *kbuf,
u8 cs;
if (kb != kbuf)
break;
- spin_lock_irq(&tty->link->ctrl.lock);
- cs = tty->link->ctrl.pktstatus;
- tty->link->ctrl.pktstatus = 0;
- spin_unlock_irq(&tty->link->ctrl.lock);
+ scoped_guard(spinlock_irq, &tty->link->ctrl.lock) {
+ cs = tty->link->ctrl.pktstatus;
+ tty->link->ctrl.pktstatus = 0;
+ }
*kb++ = cs;
nr--;
break;
@@ -2357,7 +2346,7 @@ static ssize_t n_tty_write(struct tty_struct *tty, struct file *file,
return retval;
}
- down_read(&tty->termios_rwsem);
+ guard(rwsem_read)(&tty->termios_rwsem);
/* Write out any echoed characters that are still pending */
process_echoes(tty);
@@ -2395,9 +2384,8 @@ static ssize_t n_tty_write(struct tty_struct *tty, struct file *file,
struct n_tty_data *ldata = tty->disc_data;
while (nr > 0) {
- mutex_lock(&ldata->output_lock);
- num = tty->ops->write(tty, b, nr);
- mutex_unlock(&ldata->output_lock);
+ scoped_guard(mutex, &ldata->output_lock)
+ num = tty->ops->write(tty, b, nr);
if (num < 0) {
retval = num;
goto break_out;
@@ -2424,7 +2412,7 @@ static ssize_t n_tty_write(struct tty_struct *tty, struct file *file,
remove_wait_queue(&tty->write_wait, &wait);
if (nr && tty->fasync)
set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
- up_read(&tty->termios_rwsem);
+
return (b - buf) ? b - buf : retval;
}
@@ -2498,12 +2486,11 @@ static int n_tty_ioctl(struct tty_struct *tty, unsigned int cmd,
case TIOCOUTQ:
return put_user(tty_chars_in_buffer(tty), (int __user *) arg);
case TIOCINQ:
- down_write(&tty->termios_rwsem);
- if (L_ICANON(tty) && !L_EXTPROC(tty))
- num = inq_canon(ldata);
- else
- num = read_cnt(ldata);
- up_write(&tty->termios_rwsem);
+ scoped_guard(rwsem_write, &tty->termios_rwsem)
+ if (L_ICANON(tty) && !L_EXTPROC(tty))
+ num = inq_canon(ldata);
+ else
+ num = read_cnt(ldata);
return put_user(num, (unsigned int __user *) arg);
default:
return n_tty_ioctl_helper(tty, cmd, arg);
--
2.51.1
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