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Subject[RFC PATCH 1/2] rtc: add lockless rtc_update_irq_enable
Date
Split out a function that does not acquire rtc->ops_lock from
rtc_update_irq_enable, in preparation for fixing race condition in
rtc_set_time.

Signed-off-by: Yu Liao <liaoyu15@huawei.com>
---
drivers/rtc/interface.c | 30 +++++++++++++++++++-----------
1 file changed, 19 insertions(+), 11 deletions(-)

diff --git a/drivers/rtc/interface.c b/drivers/rtc/interface.c
index 9edd662c69ac..bc55dd31bece 100644
--- a/drivers/rtc/interface.c
+++ b/drivers/rtc/interface.c
@@ -19,6 +19,7 @@

static int rtc_timer_enqueue(struct rtc_device *rtc, struct rtc_timer *timer);
static void rtc_timer_remove(struct rtc_device *rtc, struct rtc_timer *timer);
+static int __rtc_update_irq_enable(struct rtc_device *rtc, unsigned int enabled);

static void rtc_add_offset(struct rtc_device *rtc, struct rtc_time *tm)
{
@@ -81,6 +82,7 @@ static int rtc_valid_range(struct rtc_device *rtc, struct rtc_time *tm)
return 0;
}

+/* This function must be called with rtc->ops_lock held */
static int __rtc_read_time(struct rtc_device *rtc, struct rtc_time *tm)
{
int err;
@@ -553,27 +555,21 @@ int rtc_alarm_irq_enable(struct rtc_device *rtc, unsigned int enabled)
}
EXPORT_SYMBOL_GPL(rtc_alarm_irq_enable);

-int rtc_update_irq_enable(struct rtc_device *rtc, unsigned int enabled)
+static int __rtc_update_irq_enable(struct rtc_device *rtc, unsigned int enabled)
{
- int err;
-
- err = mutex_lock_interruptible(&rtc->ops_lock);
- if (err)
- return err;
+ int err = 0;

#ifdef CONFIG_RTC_INTF_DEV_UIE_EMUL
if (enabled == 0 && rtc->uie_irq_active) {
- mutex_unlock(&rtc->ops_lock);
return rtc_dev_update_irq_enable_emul(rtc, 0);
}
#endif
/* make sure we're changing state */
if (rtc->uie_rtctimer.enabled == enabled)
- goto out;
+ return err;

if (!test_bit(RTC_FEATURE_UPDATE_INTERRUPT, rtc->features) ||
!test_bit(RTC_FEATURE_ALARM, rtc->features)) {
- mutex_unlock(&rtc->ops_lock);
#ifdef CONFIG_RTC_INTF_DEV_UIE_EMUL
return rtc_dev_update_irq_enable_emul(rtc, enabled);
#else
@@ -587,7 +583,7 @@ int rtc_update_irq_enable(struct rtc_device *rtc, unsigned int enabled)

err = __rtc_read_time(rtc, &tm);
if (err)
- goto out;
+ return err;
onesec = ktime_set(1, 0);
now = rtc_tm_to_ktime(tm);
rtc->uie_rtctimer.node.expires = ktime_add(now, onesec);
@@ -597,7 +593,19 @@ int rtc_update_irq_enable(struct rtc_device *rtc, unsigned int enabled)
rtc_timer_remove(rtc, &rtc->uie_rtctimer);
}

-out:
+ return err;
+}
+
+int rtc_update_irq_enable(struct rtc_device *rtc, unsigned int enabled)
+{
+ int err;
+
+ err = mutex_lock_interruptible(&rtc->ops_lock);
+ if (err)
+ return err;
+
+ err = __rtc_update_irq_enable(rtc, enabled);
+
mutex_unlock(&rtc->ops_lock);

return err;
--
2.25.1
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