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: David Brownell <dbrownell@users.sourceforge.net>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Jonathan Corbet <corbet@lwn.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>

1 files changed, 38 insertions, 20 deletions

diff --git a/drivers/rtc/rtc-dev.c b/drivers/rtc/rtc-dev.c
index 0114a78b7cbb..0a870b7e5c32 100644
--- a/drivers/rtc/rtc-dev.c
+++ b/drivers/rtc/rtc-dev.c
@@ -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.
@@ -227,26 +231,31 @@ 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
@@ -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,