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Commit 5ad31a57 authored by David Brownell's avatar David Brownell Committed by Linus Torvalds
Browse files

rtc: remove BKL for ioctl() 



Remove implicit use of BKL in ioctl() from the RTC framework.

Instead, the rtc->ops_lock is used.  That's the same lock that already
protects the RTC operations when they're issued through the exported
rtc_*() calls in drivers/rtc/interface.c ...  making this a bugfix, not
just a cleanup, since both ioctl calls and set_alarm() need to update IRQ
enable flags and that implies a common lock (which RTC drivers as a rule
do not provide on their own).

A new comment at the declaration of "struct rtc_class_ops" summarizes
current locking rules.  It's not clear to me that the exceptions listed
there should exist ...  if not, those are pre-existing problems which can
be fixed in a patch that doesn't relate to BKL removal.

Signed-off-by: default avatarDavid Brownell <dbrownell@users.sourceforge.net>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Jonathan Corbet <corbet@lwn.net>
Acked-by: default avatarAlessandro Zummo <a.zummo@towertech.it>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 53f1b143

drivers/rtc/rtc-dev.c

+38 −20
Original line number Diff line number Diff line
@@ -209,7 +209,7 @@ static unsigned int rtc_dev_poll(struct file *file, poll_table *wait) 
	return (data != 0) ? (POLLIN | POLLRDNORM) : 0;

}



static int rtc_dev_ioctl(struct inode *inode, struct file *file,

static long rtc_dev_ioctl(struct file *file,

		unsigned int cmd, unsigned long arg)

{

	int err = 0;
@@ -219,6 +219,10 @@ static int rtc_dev_ioctl(struct inode *inode, struct file *file, 
	struct rtc_wkalrm alarm;

	void __user *uarg = (void __user *) arg;



	err = mutex_lock_interruptible(&rtc->ops_lock);

	if (err)

		return -EBUSY;



	/* check that the calling task has appropriate permissions

	 * for certain ioctls. doing this check here is useful

	 * to avoid duplicate code in each driver.
@@ -227,27 +231,32 @@ static int rtc_dev_ioctl(struct inode *inode, struct file *file, 
	case RTC_EPOCH_SET:

	case RTC_SET_TIME:

		if (!capable(CAP_SYS_TIME))

			return -EACCES;

			err = -EACCES;

		break;



	case RTC_IRQP_SET:

		if (arg > rtc->max_user_freq && !capable(CAP_SYS_RESOURCE))

			return -EACCES;

			err = -EACCES;

		break;



	case RTC_PIE_ON:

		if (rtc->irq_freq > rtc->max_user_freq &&

				!capable(CAP_SYS_RESOURCE))

			return -EACCES;

			err = -EACCES;

		break;

	}



	if (err)

		goto done;



	/* try the driver's ioctl interface */

	if (ops->ioctl) {

		err = ops->ioctl(rtc->dev.parent, cmd, arg);

		if (err != -ENOIOCTLCMD)

		if (err != -ENOIOCTLCMD) {

			mutex_unlock(&rtc->ops_lock);

			return err;

		}

	}



	/* if the driver does not provide the ioctl interface

	 * or if that particular ioctl was not implemented
@@ -265,15 +274,19 @@ static int rtc_dev_ioctl(struct inode *inode, struct file *file, 


	switch (cmd) {

	case RTC_ALM_READ:

		mutex_unlock(&rtc->ops_lock);



		err = rtc_read_alarm(rtc, &alarm);

		if (err < 0)

			return err;



		if (copy_to_user(uarg, &alarm.time, sizeof(tm)))

			return -EFAULT;

		break;

			err = -EFAULT;

		return err;



	case RTC_ALM_SET:

		mutex_unlock(&rtc->ops_lock);



		if (copy_from_user(&alarm.time, uarg, sizeof(tm)))

			return -EFAULT;
@@ -321,24 +334,26 @@ static int rtc_dev_ioctl(struct inode *inode, struct file *file, 
			}

		}



		err = rtc_set_alarm(rtc, &alarm);

		break;

		return rtc_set_alarm(rtc, &alarm);



	case RTC_RD_TIME:

		mutex_unlock(&rtc->ops_lock);



		err = rtc_read_time(rtc, &tm);

		if (err < 0)

			return err;



		if (copy_to_user(uarg, &tm, sizeof(tm)))

			return -EFAULT;

		break;

			err = -EFAULT;

		return err;



	case RTC_SET_TIME:

		mutex_unlock(&rtc->ops_lock);



		if (copy_from_user(&tm, uarg, sizeof(tm)))

			return -EFAULT;



		err = rtc_set_time(rtc, &tm);

		break;

		return rtc_set_time(rtc, &tm);



	case RTC_PIE_ON:

		err = rtc_irq_set_state(rtc, NULL, 1);
@@ -376,34 +391,37 @@ static int rtc_dev_ioctl(struct inode *inode, struct file *file, 
		break;

#endif

	case RTC_WKALM_SET:

		mutex_unlock(&rtc->ops_lock);

		if (copy_from_user(&alarm, uarg, sizeof(alarm)))

			return -EFAULT;



		err = rtc_set_alarm(rtc, &alarm);

		break;

		return rtc_set_alarm(rtc, &alarm);



	case RTC_WKALM_RD:

		mutex_unlock(&rtc->ops_lock);

		err = rtc_read_alarm(rtc, &alarm);

		if (err < 0)

			return err;



		if (copy_to_user(uarg, &alarm, sizeof(alarm)))

			return -EFAULT;

		break;

			err = -EFAULT;

		return err;



#ifdef CONFIG_RTC_INTF_DEV_UIE_EMUL

	case RTC_UIE_OFF:

		clear_uie(rtc);

		return 0;

		break;



	case RTC_UIE_ON:

		return set_uie(rtc);

		err = set_uie(rtc);

#endif

	default:

		err = -ENOTTY;

		break;

	}



done:

	mutex_unlock(&rtc->ops_lock);

	return err;

}
@@ -432,7 +450,7 @@ static const struct file_operations rtc_dev_fops = { 
	.llseek		= no_llseek,

	.read		= rtc_dev_read,

	.poll		= rtc_dev_poll,

	.ioctl		= rtc_dev_ioctl,

	.unlocked_ioctl	= rtc_dev_ioctl,

	.open		= rtc_dev_open,

	.release	= rtc_dev_release,

	.fasync		= rtc_dev_fasync,

include/linux/rtc.h

+17 −0
Original line number Diff line number Diff line
@@ -115,6 +115,23 @@ extern void rtc_time_to_tm(unsigned long time, struct rtc_time *tm); 


extern struct class *rtc_class;



/*

 * For these RTC methods the device parameter is the physical device

 * on whatever bus holds the hardware (I2C, Platform, SPI, etc), which

 * was passed to rtc_device_register().  Its driver_data normally holds

 * device state, including the rtc_device pointer for the RTC.

 *

 * Most of these methods are called with rtc_device.ops_lock held,

 * through the rtc_*(struct rtc_device *, ...) calls.

 *

 * The (current) exceptions are mostly filesystem hooks:

 *   - the proc() hook for procfs

 *   - non-ioctl() chardev hooks:  open(), release(), read_callback()

 *   - periodic irq calls:  irq_set_state(), irq_set_freq()

 *

 * REVISIT those periodic irq calls *do* have ops_lock when they're

 * issued through ioctl() ...

 */

struct rtc_class_ops {

	int (*open)(struct device *);

	void (*release)(struct device *);