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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: Jiri Kosina <jkosina@suse.cz>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: David Brownell <david-b@pacbell.net>
Acked-by: Alessandro Zummo <a.zummo@towertech.it>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Jiri Kosina 2007-12-04 23:45:05 -08:00 committed by Linus Torvalds
parent 5cd17569fd
commit 372a302e9a
2 changed files with 5 additions and 5 deletions
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4
drivers/rtc/interface.c
View File

@ -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;
}

6
drivers/rtc/rtc-dev.c
View File

@ -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;
}