Re: [PATCH] drm/msm/dp: fix event thread stuck in wait_event after kthread_sop()

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On 5/2/2022 2:50 PM, Kuogee Hsieh wrote:
Event thread supposed to exit from its while loop after kthread_stop().
However there may has possibility that event thread is pending in the
middle of wait_event due to condition checking never become true.
To make sure event thread exit its loop after kthread_stop(), this
patch OR kthread_should_stop() into wait_event's condition checking
so that event thread will exit its loop after kernal_stop().

Reported-by: Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxx>
Fixes: 570d3e5d28db ("drm/msm/dp: stop event kernel thread when DP unbind")
Signed-off-by: Kuogee Hsieh <quic_khsieh@xxxxxxxxxxx>
---
  drivers/gpu/drm/msm/dp/dp_display.c | 11 ++++++++---
  1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/msm/dp/dp_display.c b/drivers/gpu/drm/msm/dp/dp_display.c
index c388323..5200a58 100644
--- a/drivers/gpu/drm/msm/dp/dp_display.c
+++ b/drivers/gpu/drm/msm/dp/dp_display.c
@@ -1106,12 +1106,17 @@ static int hpd_event_thread(void *data)
  	while (!kthread_should_stop()) {
  		if (timeout_mode) {
  			wait_event_timeout(dp_priv->event_q,
-				(dp_priv->event_pndx == dp_priv->event_gndx),
-						EVENT_TIMEOUT);
+				((dp_priv->event_pndx == dp_priv->event_gndx) ||
+					kthread_should_stop()), EVENT_TIMEOUT);
  		} else {
  			wait_event_interruptible(dp_priv->event_q,
-				(dp_priv->event_pndx != dp_priv->event_gndx));
+				((dp_priv->event_pndx != dp_priv->event_gndx) ||
+					kthread_should_stop()));
  		}
+
+		if(kthread_should_stop())
+			break;
+
  		spin_lock_irqsave(&dp_priv->event_lock, flag);
  		todo = &dp_priv->event_list[dp_priv->event_gndx];
  		if (todo->delay) {



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