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Message-ID: <20250425111315.1036184-3-jirislaby@kernel.org>
Date: Fri, 25 Apr 2025 13:13:11 +0200
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 2/6] tty: use lock guard()s in tty_io
guard()s and scoped_guard()s express more clearly what is protected by
locks. And also makes the code cleaner as it can return immediately in
case of short returns.
Signed-off-by: Jiri Slaby (SUSE) <jirislaby@...nel.org>
---
drivers/tty/tty_io.c | 96 ++++++++++++++++++--------------------------
1 file changed, 40 insertions(+), 56 deletions(-)
diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index ca9b7d7bad2b..e2d92cf70eb7 100644
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -276,11 +276,10 @@ static void check_tty_count(struct tty_struct *tty, const char *routine)
struct list_head *p;
int count = 0, kopen_count = 0;
- spin_lock(&tty->files_lock);
- list_for_each(p, &tty->tty_files) {
- count++;
- }
- spin_unlock(&tty->files_lock);
+ scoped_guard(spinlock, &tty->files_lock)
+ list_for_each(p, &tty->tty_files)
+ count++;
+
if (tty->driver->type == TTY_DRIVER_TYPE_PTY &&
tty->driver->subtype == PTY_TYPE_SLAVE &&
tty->link && tty->link->count)
@@ -378,7 +377,7 @@ EXPORT_SYMBOL_GPL(tty_dev_name_to_number);
*/
struct tty_driver *tty_find_polling_driver(char *name, int *line)
{
- struct tty_driver *p, *res = NULL;
+ struct tty_driver *p;
int tty_line = 0;
int len;
char *str, *stp;
@@ -392,7 +391,8 @@ struct tty_driver *tty_find_polling_driver(char *name, int *line)
len = str - name;
tty_line = simple_strtoul(str, &str, 10);
- mutex_lock(&tty_mutex);
+ guard(mutex)(&tty_mutex);
+
/* Search through the tty devices to look for a match */
list_for_each_entry(p, &tty_drivers, tty_drivers) {
if (!len || strncmp(name, p->name, len) != 0)
@@ -405,14 +405,12 @@ struct tty_driver *tty_find_polling_driver(char *name, int *line)
if (tty_line >= 0 && tty_line < p->num && p->ops &&
p->ops->poll_init && !p->ops->poll_init(p, tty_line, stp)) {
- res = tty_driver_kref_get(p);
*line = tty_line;
- break;
+ return tty_driver_kref_get(p);
}
}
- mutex_unlock(&tty_mutex);
- return res;
+ return NULL;
}
EXPORT_SYMBOL_GPL(tty_find_polling_driver);
#endif
@@ -531,16 +529,15 @@ EXPORT_SYMBOL_GPL(tty_wakeup);
*/
static struct file *tty_release_redirect(struct tty_struct *tty)
{
- struct file *f = NULL;
+ guard(spinlock)(&redirect_lock);
- spin_lock(&redirect_lock);
if (redirect && file_tty(redirect) == tty) {
- f = redirect;
+ struct file *f = redirect;
redirect = NULL;
+ return f;
}
- spin_unlock(&redirect_lock);
- return f;
+ return NULL;
}
/**
@@ -765,11 +762,8 @@ void __stop_tty(struct tty_struct *tty)
*/
void stop_tty(struct tty_struct *tty)
{
- unsigned long flags;
-
- spin_lock_irqsave(&tty->flow.lock, flags);
+ guard(spinlock_irqsave)(&tty->flow.lock);
__stop_tty(tty);
- spin_unlock_irqrestore(&tty->flow.lock, flags);
}
EXPORT_SYMBOL(stop_tty);
@@ -796,11 +790,8 @@ void __start_tty(struct tty_struct *tty)
*/
void start_tty(struct tty_struct *tty)
{
- unsigned long flags;
-
- spin_lock_irqsave(&tty->flow.lock, flags);
+ guard(spinlock_irqsave)(&tty->flow.lock);
__start_tty(tty);
- spin_unlock_irqrestore(&tty->flow.lock, flags);
}
EXPORT_SYMBOL(start_tty);
@@ -809,7 +800,8 @@ static void tty_update_time(struct tty_struct *tty, bool mtime)
time64_t sec = ktime_get_real_seconds();
struct tty_file_private *priv;
- spin_lock(&tty->files_lock);
+ guard(spinlock)(&tty->files_lock);
+
list_for_each_entry(priv, &tty->tty_files, list) {
struct inode *inode = file_inode(priv->file);
struct timespec64 time = mtime ? inode_get_mtime(inode) : inode_get_atime(inode);
@@ -827,7 +819,6 @@ static void tty_update_time(struct tty_struct *tty, bool mtime)
inode_set_atime(inode, sec, 0);
}
}
- spin_unlock(&tty->files_lock);
}
/*
@@ -2314,13 +2305,12 @@ static int tiocsti(struct tty_struct *tty, u8 __user *p)
*/
static int tiocgwinsz(struct tty_struct *tty, struct winsize __user *arg)
{
- int err;
+ guard(mutex)(&tty->winsize_mutex);
- mutex_lock(&tty->winsize_mutex);
- err = copy_to_user(arg, &tty->winsize, sizeof(*arg));
- mutex_unlock(&tty->winsize_mutex);
+ if (copy_to_user(arg, &tty->winsize, sizeof(*arg)))
+ return -EFAULT;
- return err ? -EFAULT : 0;
+ return 0;
}
/**
@@ -2335,10 +2325,10 @@ int tty_do_resize(struct tty_struct *tty, struct winsize *ws)
{
struct pid *pgrp;
- /* Lock the tty */
- mutex_lock(&tty->winsize_mutex);
+ guard(mutex)(&tty->winsize_mutex);
+
if (!memcmp(ws, &tty->winsize, sizeof(*ws)))
- goto done;
+ return 0;
/* Signal the foreground process group */
pgrp = tty_get_pgrp(tty);
@@ -2347,8 +2337,7 @@ int tty_do_resize(struct tty_struct *tty, struct winsize *ws)
put_pid(pgrp);
tty->winsize = *ws;
-done:
- mutex_unlock(&tty->winsize_mutex);
+
return 0;
}
EXPORT_SYMBOL(tty_do_resize);
@@ -2409,13 +2398,14 @@ static int tioccons(struct file *file)
return -EBADF;
if (!(file->f_mode & FMODE_CAN_WRITE))
return -EINVAL;
- spin_lock(&redirect_lock);
- if (redirect) {
- spin_unlock(&redirect_lock);
+
+ guard(spinlock)(&redirect_lock);
+
+ if (redirect)
return -EBUSY;
- }
+
redirect = get_file(file);
- spin_unlock(&redirect_lock);
+
return 0;
}
@@ -3028,11 +3018,9 @@ void __do_SAK(struct tty_struct *tty)
struct task_struct *g, *p;
struct pid *session;
int i;
- unsigned long flags;
- spin_lock_irqsave(&tty->ctrl.lock, flags);
- session = get_pid(tty->ctrl.session);
- spin_unlock_irqrestore(&tty->ctrl.lock, flags);
+ scoped_guard(spinlock_irqsave, &tty->ctrl.lock)
+ session = get_pid(tty->ctrl.session);
tty_ldisc_flush(tty);
@@ -3055,7 +3043,7 @@ void __do_SAK(struct tty_struct *tty)
PIDTYPE_SID);
continue;
}
- task_lock(p);
+ guard(task_lock)(p);
i = iterate_fd(p->files, 0, this_tty, tty);
if (i != 0) {
tty_notice(tty, "SAK: killed process %d (%s): by fd#%d\n",
@@ -3063,7 +3051,6 @@ void __do_SAK(struct tty_struct *tty)
group_send_sig_info(SIGKILL, SEND_SIG_PRIV, p,
PIDTYPE_SID);
}
- task_unlock(p);
}
read_unlock(&tasklist_lock);
put_pid(session);
@@ -3465,9 +3452,8 @@ int tty_register_driver(struct tty_driver *driver)
goto err_unreg_char;
}
- mutex_lock(&tty_mutex);
- list_add(&driver->tty_drivers, &tty_drivers);
- mutex_unlock(&tty_mutex);
+ scoped_guard(mutex, &tty_mutex)
+ list_add(&driver->tty_drivers, &tty_drivers);
if (!(driver->flags & TTY_DRIVER_DYNAMIC_DEV)) {
for (i = 0; i < driver->num; i++) {
@@ -3486,9 +3472,8 @@ int tty_register_driver(struct tty_driver *driver)
for (i--; i >= 0; i--)
tty_unregister_device(driver, i);
- mutex_lock(&tty_mutex);
- list_del(&driver->tty_drivers);
- mutex_unlock(&tty_mutex);
+ scoped_guard(mutex, &tty_mutex)
+ list_del(&driver->tty_drivers);
err_unreg_char:
unregister_chrdev_region(dev, driver->num);
@@ -3507,9 +3492,8 @@ void tty_unregister_driver(struct tty_driver *driver)
{
unregister_chrdev_region(MKDEV(driver->major, driver->minor_start),
driver->num);
- mutex_lock(&tty_mutex);
- list_del(&driver->tty_drivers);
- mutex_unlock(&tty_mutex);
+ scoped_guard(mutex, &tty_mutex)
+ list_del(&driver->tty_drivers);
}
EXPORT_SYMBOL(tty_unregister_driver);
--
2.49.0
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