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@kernel.org>
Link: https://patch.msgid.link/20251119100140.830761-3-jirislaby@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/n_tty.c b/drivers/tty/n_tty.c
index 6af3f3a0b53149765438f7b14ea9422b76a84197..e6a0f5b40d0a56e3b31ffb2a3cf1b4ce50a48e44 100644 (file)
--- 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 @@ break_out:
        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);