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Message-ID: <834eeda0-12b0-3f16-8ca2-89175c1de186@linaro.org>
Date: Wed, 4 May 2022 21:38:05 +0300
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Kuogee Hsieh <quic_khsieh@...cinc.com>, robdclark@...il.com,
sean@...rly.run, swboyd@...omium.org, dianders@...omium.org,
vkoul@...nel.org, daniel@...ll.ch, airlied@...ux.ie,
agross@...nel.org, bjorn.andersson@...aro.org
Cc: quic_abhinavk@...cinc.com, quic_aravindh@...cinc.com,
quic_sbillaka@...cinc.com, freedreno@...ts.freedesktop.org,
dri-devel@...ts.freedesktop.org, linux-arm-msm@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] drm/msm/dp: fix event thread stuck in wait_event after
kthread_stop()
On 03/05/2022 19:25, 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().
>
> 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@...aro.org>
> Fixes: 570d3e5d28db ("drm/msm/dp: stop event kernel thread when DP unbind")
> Signed-off-by: Kuogee Hsieh <quic_khsieh@...cinc.com>
Let's do it properly:
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.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 c388323..da5c03a 100644
> --- a/drivers/gpu/drm/msm/dp/dp_display.c
> +++ b/drivers/gpu/drm/msm/dp/dp_display.c
> @@ -1103,15 +1103,20 @@ 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) {
--
With best wishes
Dmitry
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