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drm: Limit the number of .get_vblank_counter() retries

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Pontential infinite loops in the vblank code are a bad idea. Add some
limits.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
This commit is contained in:
Ville Syrjälä 2015-09-14 22:43:48 +03:00 committed by Daniel Vetter
parent a6e610dcce
commit facfb062e8
1 changed files with 4 additions and 2 deletions
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6
drivers/gpu/drm/drm_irq.c
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@ -127,6 +127,7 @@ static void drm_update_vblank_count(struct drm_device *dev, unsigned int pipe,
u32 cur_vblank, diff;
bool rc;
struct timeval t_vblank;
int count = DRM_TIMESTAMP_MAXRETRIES;
/*
* Interrupts were disabled prior to this call, so deal with counter
@ -143,7 +144,7 @@ static void drm_update_vblank_count(struct drm_device *dev, unsigned int pipe,
do {
cur_vblank = dev->driver->get_vblank_counter(dev, pipe);
rc = drm_get_last_vbltimestamp(dev, pipe, &t_vblank, flags);
} while (cur_vblank != dev->driver->get_vblank_counter(dev, pipe));
} while (cur_vblank != dev->driver->get_vblank_counter(dev, pipe) && --count > 0);
/* Deal with counter wrap */
diff = cur_vblank - vblank->last;
@ -914,6 +915,7 @@ u32 drm_vblank_count_and_time(struct drm_device *dev, unsigned int pipe,
struct timeval *vblanktime)
{
struct drm_vblank_crtc *vblank = &dev->vblank[pipe];
int count = DRM_TIMESTAMP_MAXRETRIES;
u32 cur_vblank;
if (WARN_ON(pipe >= dev->num_crtcs))
@ -929,7 +931,7 @@ u32 drm_vblank_count_and_time(struct drm_device *dev, unsigned int pipe,
smp_rmb();
*vblanktime = vblanktimestamp(dev, pipe, cur_vblank);
smp_rmb();
} while (cur_vblank != vblank->count);
} while (cur_vblank != vblank->count && --count > 0);
return cur_vblank;
}