gpiolib: fix line event timestamps for nested irqs

From: Bartosz Golaszewski <[email protected]>

Nested interrupts run inside the calling thread's context and the top half handler is never called which means that we never read the timestamp.

This issue came up when trying to read line events from a gpiochip using regmap_irq_chip for interrupts.

Fix it by reading the timestamp from the irq thread function if it's still 0 by the time the second handler is called.

---
v1 -> v2:
- add Fixes: to the commit message and Cc stable
- directly assing ktime_get_real_ns() to ge.timestamp

 drivers/gpio/gpiolib.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

index 1651d7f0a303..d1adfdf50fb3 100644
@@ -828,7 +828,14 @@ static irqreturn_t lineevent_irq_thread(int irq, void *p)
 	/* Do not leak kernel stack to userspace */
 	memset(&ge, 0, sizeof(ge));
 
-	ge.timestamp = le->timestamp;
+	/*
+	 * We may be running from a nested threaded interrupt in which case
+	 * we didn't get the timestamp from lineevent_irq_handler().
+	 */
+	if (!le->timestamp)
+		ge.timestamp = ktime_get_real_ns();
+	else
+		ge.timestamp = le->timestamp;
 
 	if (le->eflags & GPIOEVENT_REQUEST_RISING_EDGE
 	    && le->eflags & GPIOEVENT_REQUEST_FALLING_EDGE) {

2.19.1

śr., 16 sty 2019 o 14:35 Sasha Levin <[email protected]> napisał(a):

I sent a backport of this patch.

Bart