On Wed, Jul 22, 2020 at 01:05:27AM +0000, Xu Qiang wrote:
> The drm_handle_vblank function is in the interrupt context.
> Therefore, the spin lock vblank_time_lock is obtained
> from the interrupt context.
>
> Cc: <[email protected]>
> Signed-off-by: Xu Qiang <[email protected]>
> ---
> drivers/gpu/drm/drm_vblank.c | 17 ++++++++++-------
> 1 file changed, 10 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_vblank.c b/drivers/gpu/drm/drm_vblank.c
> index f402c75b9d34..4ca63ff33a43 100644
> --- a/drivers/gpu/drm/drm_vblank.c
> +++ b/drivers/gpu/drm/drm_vblank.c
> @@ -229,10 +229,11 @@ static void drm_reset_vblank_timestamp(struct
> drm_device *dev, unsigned int pipe
> {
> u32 cur_vblank;
> bool rc;
> + unsigned long irqflags;
> ktime_t t_vblank;
> int count = DRM_TIMESTAMP_MAXRETRIES;
>
> - spin_lock(&dev->vblank_time_lock);
> + spin_lock_irqsave(&dev->vblank_time_lock, irqflags);
Nak. This is always called with interrupts off, so no point on wasting
time saving/restoring the flags. And it's the same situation for all the
other cases you have below.
>
> /*
> * sample the current counter to avoid random jumps
> @@ -257,7 +258,7 @@ static void drm_reset_vblank_timestamp(struct drm_device
> *dev, unsigned int pipe
> */
> store_vblank(dev, pipe, 1, t_vblank, cur_vblank);
>
> - spin_unlock(&dev->vblank_time_lock);
> + spin_unlock_irqrestore(&dev->vblank_time_lock, irqflags);
> }
>
> /*
> @@ -1106,11 +1107,12 @@ static int __enable_vblank(struct drm_device *dev,
> unsigned int pipe)
> static int drm_vblank_enable(struct drm_device *dev, unsigned int pipe)
> {
> struct drm_vblank_crtc *vblank = &dev->vblank[pipe];
> + unsigned long irqflags;
> int ret = 0;
>
> assert_spin_locked(&dev->vbl_lock);
>
> - spin_lock(&dev->vblank_time_lock);
> + spin_lock_irqsave(&dev->vblank_time_lock, irqflags);
>
> if (!vblank->enabled) {
> /*
> @@ -1136,7 +1138,7 @@ static int drm_vblank_enable(struct drm_device *dev,
> unsigned int pipe)
> }
> }
>
> - spin_unlock(&dev->vblank_time_lock);
> + spin_unlock_irqrestore(&dev->vblank_time_lock, irqflags);
>
> return ret;
> }
> @@ -1917,6 +1919,7 @@ bool drm_handle_vblank(struct drm_device *dev, unsigned
> int pipe)
> {
> struct drm_vblank_crtc *vblank = &dev->vblank[pipe];
> unsigned long irqflags;
> + unsigned long irqflags_vblank;
> bool disable_irq;
>
> if (drm_WARN_ON_ONCE(dev, !drm_dev_has_vblank(dev)))
> @@ -1931,18 +1934,18 @@ bool drm_handle_vblank(struct drm_device *dev,
> unsigned int pipe)
> * vblank enable/disable, as this would cause inconsistent
> * or corrupted timestamps and vblank counts.
> */
> - spin_lock(&dev->vblank_time_lock);
> + spin_lock_irqsave(&dev->vblank_time_lock, irqflags_vblank);
>
> /* Vblank irq handling disabled. Nothing to do. */
> if (!vblank->enabled) {
> - spin_unlock(&dev->vblank_time_lock);
> + spin_unlock_irqrestore(&dev->vblank_time_lock, irqflags_vblank);
> spin_unlock_irqrestore(&dev->event_lock, irqflags);
> return false;
> }
>
> drm_update_vblank_count(dev, pipe, true);
>
> - spin_unlock(&dev->vblank_time_lock);
> + spin_unlock_irqrestore(&dev->vblank_time_lock, irqflags_vblank);
>
> wake_up(&vblank->queue);
>
> --
> 2.25.0
>
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> https://lists.freedesktop.org/mailman/listinfo/dri-devel
--
Ville Syrjälä
Intel
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