[PATCH STABLE v4.19.15] gpiolib: fix line event timestamps for nested irqs

[PATCH STABLE v4.19.15] gpiolib: fix line event timestamps for nested irqs

[Bartosz Golaszewski]

From: Bartosz Golaszewski <bgolaszewski@baylibre.com>

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.

Fixes: d58f2bf261fd ("gpio: Timestamp events in hardirq handler")
Cc: stable@vger.kernel.org
Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
---
Hi Sasha,

this is a backport for v4.19.y series. The original patch didn't apply
due to a conflict.

 drivers/gpio/gpiolib.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index a8e01d99919c..b3ab6c428423 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -817,7 +817,15 @@ 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;
+
 	level = gpiod_get_value_cansleep(le->desc);
 
 	if (le->eflags & GPIOEVENT_REQUEST_RISING_EDGE
-- 
2.19.1

Re: [PATCH STABLE v4.19.15] gpiolib: fix line event timestamps for nested irqs

[Greg KH]

On Wed, Jan 16, 2019 at 04:35:57PM +0100, Bartosz Golaszewski wrote:
> From: Bartosz Golaszewski <bgolaszewski@baylibre.com>
> 
> 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.
> 
> Fixes: d58f2bf261fd ("gpio: Timestamp events in hardirq handler")
> Cc: stable@vger.kernel.org
> Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
> ---
> Hi Sasha,
> 
> this is a backport for v4.19.y series. The original patch didn't apply
> due to a conflict.

What is the git commit id for this patch in Linus's tree?

thanks,

greg k-h

Re: [PATCH STABLE v4.19.15] gpiolib: fix line event timestamps for nested irqs

[Bartosz Golaszewski]

śr., 16 sty 2019 o 17:02 Greg KH <greg@kroah.com> napisał(a):
>
> On Wed, Jan 16, 2019 at 04:35:57PM +0100, Bartosz Golaszewski wrote:
> > From: Bartosz Golaszewski <bgolaszewski@baylibre.com>
> >
> > 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.
> >
> > Fixes: d58f2bf261fd ("gpio: Timestamp events in hardirq handler")
> > Cc: stable@vger.kernel.org
> > Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
> > ---
> > Hi Sasha,
> >
> > this is a backport for v4.19.y series. The original patch didn't apply
> > due to a conflict.
>
> What is the git commit id for this patch in Linus's tree?
>

I'm not sure if you mean Linus Torvalds or Linus Walleij (through whom
my GPIO patches go) but neither has picked this one up yet. I'm not
sure why it got processed for stable already, I thought it must go
into Linus Torvalds' master branch first.

Anyway, in my GPIO branch its commit id is
8d694dcdbbdcfe4f27a52bcc6f2ce733ba5ec53c and it should get merged into
Linus Walleij's tree soon. I have already sent a PR.

Best regards,
Bartosz Golaszewski