2022-05-03 00:24:37

by Kuogee Hsieh

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

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().

Fixes: 570d3e5d28db ("drm/msm/dp: stop event kernel thread when DP unbind")
Signed-off-by: Kuogee Hsieh <[email protected]>
---
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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a Linux Foundation Collaborative Project

2022-05-03 00:55:47

by Abhinav Kumar

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

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 <[email protected]>
> Fixes: 570d3e5d28db ("drm/msm/dp: stop event kernel thread when DP unbind")
> Signed-off-by: Kuogee Hsieh <[email protected]>
> ---
> 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) {