From 5ad31a575157147b43fa84ef1e21471661653878 Mon Sep 17 00:00:00 2001 From: David Brownell Date: Wed, 23 Jul 2008 21:30:33 -0700 Subject: [PATCH] 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 Cc: Alan Cox Cc: Jonathan Corbet Acked-by: Alessandro Zummo Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- drivers/rtc/rtc-dev.c | 58 ++++++++++++++++++++++++++++--------------- include/linux/rtc.h | 17 +++++++++++++ 2 files changed, 55 insertions(+), 20 deletions(-) diff --git a/drivers/rtc/rtc-dev.c b/drivers/rtc/rtc-dev.c index 0114a78b7cb..0a870b7e5c3 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, diff --git a/include/linux/rtc.h b/include/linux/rtc.h index f2d0d152772..b01fe004cb5 100644 --- a/include/linux/rtc.h +++ b/include/linux/rtc.h @@ -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 *); -- 2.41.0