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: stable@vger.kernel.org Signed-off-by: Xu Qiang xuqiang36@huawei.com

---

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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