Revert
commit 6950d046eb6e ("rtc: cmos: Replace spin_lock_irqsave with spin_lock in hard IRQ")
and add a comment.
As described in a previous
commit 66e4f4a9cc38 ("rtc: cmos: Use spin_lock_irqsave() in cmos_interrupt()")
from February 2020:
cmos_interrupt() isn't always called from hardirq context, so
we must use spin_lock_irqsave() & co.
Indeed, cmos_interrupt() is called from cmos_check_wkalrm(), which is
called from cmos_resume() - apparently not in an interrupt context.
A later
commit 6950d046eb6e ("rtc: cmos: Replace spin_lock_irqsave with spin_lock in hard IRQ")
did not take account of this and changed spin_lock_irqsave() to spin_lock().
This may cause a deadlock as quoted in the body of
commit 66e4f4a9cc38 ("rtc: cmos: Use spin_lock_irqsave() in cmos_interrupt()")
mentioned earlier.
Signed-off-by: Mateusz Jończyk <mat.jonczyk@xxxxx>
Cc: Alessandro Zummo <a.zummo@xxxxxxxxxxxx>
Cc: Alexandre Belloni <alexandre.belloni@xxxxxxxxxxx>
Cc: Ville Syrjälä <ville.syrjala@xxxxxxxxxxxxxxx>
Cc: Xiaofei Tan <tanxiaofei@xxxxxxxxxx>
---
drivers/rtc/rtc-cmos.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/drivers/rtc/rtc-cmos.c b/drivers/rtc/rtc-cmos.c
index c24465f7bed4..508fba8746a1 100644
--- a/drivers/rtc/rtc-cmos.c
+++ b/drivers/rtc/rtc-cmos.c
@@ -741,10 +741,14 @@ static struct cmos_rtc cmos_rtc;
static irqreturn_t cmos_interrupt(int irq, void *p)
{
+ unsigned long flags;
u8 irqstat;
u8 rtc_control;
- spin_lock(&rtc_lock);
+ /* cmos_interrupt() may be called from cmos_check_wkalrm() not in
+ * interrupt context, so using spin_lock_irqsave() is required
+ */
+ spin_lock_irqsave(&rtc_lock, flags);
/* When the HPET interrupt handler calls us, the interrupt
* status is passed as arg1 instead of the irq number. But
@@ -778,7 +782,7 @@ static irqreturn_t cmos_interrupt(int irq, void *p)
hpet_mask_rtc_irq_bit(RTC_AIE);
CMOS_READ(RTC_INTR_FLAGS);
}
- spin_unlock(&rtc_lock);
+ spin_unlock_irqrestore(&rtc_lock, flags);
if (is_intr(irqstat)) {
rtc_update_irq(p, 1, irqstat);
--
2.25.1
