[BUG] rtc uie emulation deadlocks

Russell King
2008-08-11T13:44:12Z

With CONFIG_RTC_INTF_DEV_UIE_EMUL=y, hwclock deadlocks in rtc_read_time
due to:

static long rtc_dev_ioctl(struct file *file,
unsigned int cmd, unsigned long arg)
{
err = mutex_lock_interruptible(&rtc->ops_lock);
if (err)
return err;
...
switch (cmd) {
#ifdef CONFIG_RTC_INTF_DEV_UIE_EMUL
case RTC_UIE_OFF:
clear_uie(rtc);
break;

case RTC_UIE_ON:
err = set_uie(rtc);
#endif
}

static int set_uie(struct rtc_device *rtc)
{
err = rtc_read_time(rtc, &tm);
...

int rtc_read_time(struct rtc_device *rtc, struct rtc_time *tm)
{
err = mutex_lock_interruptible(&rtc->ops_lock);

So we try to take the same lock twice... Not good.

The locking looks a rather random in there, so I'm not going to try to
create a patch.

--
Russell King
Linux kernel 2.6 ARM Linux - http://www.arm.linux.org.uk/