From: Bartosz Golaszewski <brgl@bgdev.pl>
To: Linus Walleij <linus.walleij@linaro.org>,
Kent Gibson <warthog618@gmail.com>, Alex Elder <elder@linaro.org>,
Geert Uytterhoeven <geert+renesas@glider.be>,
"Paul E . McKenney" <paulmck@kernel.org>,
Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
Wolfram Sang <wsa@the-dreams.de>
Cc: linux-gpio@vger.kernel.org, linux-kernel@vger.kernel.org,
Bartosz Golaszewski <bartosz.golaszewski@linaro.org>,
kernel test robot <oliver.sang@intel.com>
Subject: [PATCH 2/3] gpio: cdev: use correct pointer accessors with SRCU
Date: Tue, 13 Feb 2024 10:31:07 +0100 [thread overview]
Message-ID: <20240213093108.13922-3-brgl@bgdev.pl> (raw)
In-Reply-To: <20240213093108.13922-1-brgl@bgdev.pl>
From: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
We never dereference the chip pointer in character device code so we can
use the lighter rcu_access_pointer() helper. This also makes lockep
happier as it no longer complains about suspicious rcu_dereference()
usage.
Fixes: d83cee3d2bb1 ("gpio: protect the pointer to gpio_chip in gpio_device with SRCU")
Reported-by: kernel test robot <oliver.sang@intel.com>
Closes: https://lore.kernel.org/oe-lkp/202402122234.d85cca9b-lkp@intel.com
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
---
drivers/gpio/gpiolib-cdev.c | 25 ++++++++++++-------------
1 file changed, 12 insertions(+), 13 deletions(-)
diff --git a/drivers/gpio/gpiolib-cdev.c b/drivers/gpio/gpiolib-cdev.c
index 9323b357df43..85037fa4925e 100644
--- a/drivers/gpio/gpiolib-cdev.c
+++ b/drivers/gpio/gpiolib-cdev.c
@@ -206,7 +206,7 @@ static long linehandle_ioctl(struct file *file, unsigned int cmd,
guard(srcu)(&lh->gdev->srcu);
- if (!rcu_dereference(lh->gdev->chip))
+ if (!rcu_access_pointer(lh->gdev->chip))
return -ENODEV;
switch (cmd) {
@@ -1521,7 +1521,7 @@ static long linereq_ioctl(struct file *file, unsigned int cmd,
guard(srcu)(&lr->gdev->srcu);
- if (!rcu_dereference(lr->gdev->chip))
+ if (!rcu_access_pointer(lr->gdev->chip))
return -ENODEV;
switch (cmd) {
@@ -1552,7 +1552,7 @@ static __poll_t linereq_poll(struct file *file,
guard(srcu)(&lr->gdev->srcu);
- if (!rcu_dereference(lr->gdev->chip))
+ if (!rcu_access_pointer(lr->gdev->chip))
return EPOLLHUP | EPOLLERR;
poll_wait(file, &lr->wait, wait);
@@ -1574,7 +1574,7 @@ static ssize_t linereq_read(struct file *file, char __user *buf,
guard(srcu)(&lr->gdev->srcu);
- if (!rcu_dereference(lr->gdev->chip))
+ if (!rcu_access_pointer(lr->gdev->chip))
return -ENODEV;
if (count < sizeof(le))
@@ -1875,7 +1875,7 @@ static __poll_t lineevent_poll(struct file *file,
guard(srcu)(&le->gdev->srcu);
- if (!rcu_dereference(le->gdev->chip))
+ if (!rcu_access_pointer(le->gdev->chip))
return EPOLLHUP | EPOLLERR;
poll_wait(file, &le->wait, wait);
@@ -1913,7 +1913,7 @@ static ssize_t lineevent_read(struct file *file, char __user *buf,
guard(srcu)(&le->gdev->srcu);
- if (!rcu_dereference(le->gdev->chip))
+ if (!rcu_access_pointer(le->gdev->chip))
return -ENODEV;
/*
@@ -1996,7 +1996,7 @@ static long lineevent_ioctl(struct file *file, unsigned int cmd,
guard(srcu)(&le->gdev->srcu);
- if (!rcu_dereference(le->gdev->chip))
+ if (!rcu_access_pointer(le->gdev->chip))
return -ENODEV;
/*
@@ -2510,7 +2510,7 @@ static long gpio_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
guard(srcu)(&gdev->srcu);
/* We fail any subsequent ioctl():s when the chip is gone */
- if (!rcu_dereference(gdev->chip))
+ if (!rcu_access_pointer(gdev->chip))
return -ENODEV;
/* Fill in the struct and pass to userspace */
@@ -2595,7 +2595,7 @@ static __poll_t lineinfo_watch_poll(struct file *file,
guard(srcu)(&cdev->gdev->srcu);
- if (!rcu_dereference(cdev->gdev->chip))
+ if (!rcu_access_pointer(cdev->gdev->chip))
return EPOLLHUP | EPOLLERR;
poll_wait(file, &cdev->wait, pollt);
@@ -2618,7 +2618,7 @@ static ssize_t lineinfo_watch_read(struct file *file, char __user *buf,
guard(srcu)(&cdev->gdev->srcu);
- if (!rcu_dereference(cdev->gdev->chip))
+ if (!rcu_access_pointer(cdev->gdev->chip))
return -ENODEV;
#ifndef CONFIG_GPIO_CDEV_V1
@@ -2696,7 +2696,7 @@ static int gpio_chrdev_open(struct inode *inode, struct file *file)
guard(srcu)(&gdev->srcu);
/* Fail on open if the backing gpiochip is gone */
- if (!rcu_dereference(gdev->chip))
+ if (!rcu_access_pointer(gdev->chip))
return -ENODEV;
cdev = kzalloc(sizeof(*cdev), GFP_KERNEL);
@@ -2796,8 +2796,7 @@ int gpiolib_cdev_register(struct gpio_device *gdev, dev_t devt)
guard(srcu)(&gdev->srcu);
- gc = rcu_dereference(gdev->chip);
- if (!gc)
+ if (!rcu_access_pointer(gdev->chip))
return -ENODEV;
chip_dbg(gc, "added GPIO chardev (%d:%d)\n", MAJOR(devt), gdev->id);
--
2.40.1
next prev parent reply other threads:[~2024-02-13 9:31 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-02-13 9:31 [PATCH 0/3] gpio: fix SRCU bugs Bartosz Golaszewski
2024-02-13 9:31 ` [PATCH 1/3] gpio: take the SRCU read lock in gpiod_hog() Bartosz Golaszewski
2024-02-13 21:29 ` Linus Walleij
2024-02-13 9:31 ` Bartosz Golaszewski [this message]
2024-02-13 21:33 ` [PATCH 2/3] gpio: cdev: use correct pointer accessors with SRCU Linus Walleij
2024-02-13 9:31 ` [PATCH 3/3] gpio: use rcu_dereference_protected() to make lockdep happy Bartosz Golaszewski
2024-02-13 12:03 ` Paul E. McKenney
2024-02-13 12:06 ` Bartosz Golaszewski
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