[PATCH 5.17 339/772] drm/msm/dp: fix event thread stuck in wait_event after kthread_stop()

Greg Kroah-Hartman
2022-06-07T21:06:38Z

From: Kuogee Hsieh <quic_khsieh@quicinc.com>

[ Upstream commit 2f9b5b3ae2eb625b75a898212a76f3b8c6d0d2b0 ]

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().

Changes in v2:
-- correct spelling error at commit title

Changes in v3:
-- remove unnecessary parenthesis
-- while(1) to replace while (!kthread_should_stop())

Reported-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Fixes: 570d3e5d28db ("drm/msm/dp: stop event kernel thread when DP unbind")
Signed-off-by: Kuogee Hsieh <quic_khsieh@quicinc.com>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Reviewed-by: Stephen Boyd <swboyd@chromium.org>
Patchwork: https://patchwork.freedesktop.org/patch/484576/
Link: https://lore.kernel.org/r/1651595136-24312-1-git-send-email-quic_khsieh@quicinc.com
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/gpu/drm/msm/dp/dp_display.c | 13 +++++++++----
1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/msm/dp/dp_display.c b/drivers/gpu/drm/msm/dp/dp_display.c
index fb424f8b29e5..2baa1ad54899 100644
--- a/drivers/gpu/drm/msm/dp/dp_display.c
+++ b/drivers/gpu/drm/msm/dp/dp_display.c
@@ -1065,15 +1065,20 @@ static int hpd_event_thread(void *data)

dp_priv = (struct dp_display_private *)data;

- while (!kthread_should_stop()) {
+ while (1) {
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) {
--
2.35.1