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Commit 372a302e authored by Jiri Kosina's avatar Jiri Kosina Committed by Linus Torvalds
Browse files

RTC: assure proper memory ordering with respect to RTC_DEV_BUSY flag 



We must make sure that the RTC_DEV_BUSY flag has proper lock semantics,
i.e.  that the RTC_DEV_BUSY stores clearing the flag don't get reordered
before the preceeding stores and loads and vice versa.

Spotted by Nick Piggin.

Signed-off-by: default avatarJiri Kosina <jkosina@suse.cz>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: David Brownell <david-b@pacbell.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 5cd17569

drivers/rtc/interface.c

+2 −2
Original line number Diff line number Diff line
@@ -293,7 +293,7 @@ int rtc_irq_register(struct rtc_device *rtc, struct rtc_task *task) 
		return -EINVAL;



	/* Cannot register while the char dev is in use */

	if (test_and_set_bit(RTC_DEV_BUSY, &rtc->flags))

	if (test_and_set_bit_lock(RTC_DEV_BUSY, &rtc->flags))

		return -EBUSY;



	spin_lock_irq(&rtc->irq_task_lock);
@@ -303,7 +303,7 @@ int rtc_irq_register(struct rtc_device *rtc, struct rtc_task *task) 
	}

	spin_unlock_irq(&rtc->irq_task_lock);



	clear_bit(RTC_DEV_BUSY, &rtc->flags);

	clear_bit_unlock(RTC_DEV_BUSY, &rtc->flags);



	return retval;

}

drivers/rtc/rtc-dev.c

+3 −3
Original line number Diff line number Diff line
@@ -26,7 +26,7 @@ static int rtc_dev_open(struct inode *inode, struct file *file) 
					struct rtc_device, char_dev);

	const struct rtc_class_ops *ops = rtc->ops;



	if (test_and_set_bit(RTC_DEV_BUSY, &rtc->flags))

	if (test_and_set_bit_lock(RTC_DEV_BUSY, &rtc->flags))

		return -EBUSY;



	file->private_data = rtc;
@@ -41,7 +41,7 @@ static int rtc_dev_open(struct inode *inode, struct file *file) 
	}



	/* something has gone wrong */

	clear_bit(RTC_DEV_BUSY, &rtc->flags);

	clear_bit_unlock(RTC_DEV_BUSY, &rtc->flags);

	return err;

}
@@ -402,7 +402,7 @@ static int rtc_dev_release(struct inode *inode, struct file *file) 
	if (rtc->ops->release)

		rtc->ops->release(rtc->dev.parent);



	clear_bit(RTC_DEV_BUSY, &rtc->flags);

	clear_bit_unlock(RTC_DEV_BUSY, &rtc->flags);

	return 0;

}