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drm: omapdrm: Fix page flip race with CRTC disable 

We can't rely on crtc->primary->fb in the page flip worker, as a racing
CRTC disable (due for instance to an explicit framebuffer deletion from
userspace) would set that field to NULL before the worker gets a change
to run. Store the framebuffer queued for page flip in a new field of
omap_crtc instead, and hold a reference to it.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
This commit is contained in:
Laurent Pinchart 2015-03-04 18:24:18 +02:00
parent c397cfd496
commit 0c19ac9d03
1 changed files with 19 additions and 5 deletions
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24
drivers/gpu/drm/omapdrm/omap_crtc.c
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@ -66,7 +66,8 @@ struct omap_crtc {
* page queue has been submitted, WAIT when waiting for GEM async * page queue has been submitted, WAIT when waiting for GEM async
* completion, QUEUED when the page flip has been queued to the hardware * completion, QUEUED when the page flip has been queued to the hardware
* or CANCELLED when the CRTC is turned off before the flip gets queued * or CANCELLED when the CRTC is turned off before the flip gets queued
* to the hardware. The flip event, if any, is stored in flip_event. The * to the hardware. The flip event, if any, is stored in flip_event, and
* the framebuffer queued for page flip is stored in flip_fb. The
* flip_wait wait queue is used to wait for page flip completion. * flip_wait wait queue is used to wait for page flip completion.
* *
* The flip_work work queue handles page flip requests without caring * The flip_work work queue handles page flip requests without caring
@ -76,6 +77,7 @@ struct omap_crtc {
*/ */
enum omap_page_flip_state flip_state; enum omap_page_flip_state flip_state;
struct drm_pending_vblank_event *flip_event; struct drm_pending_vblank_event *flip_event;
struct drm_framebuffer *flip_fb;
wait_queue_head_t flip_wait; wait_queue_head_t flip_wait;
struct work_struct flip_work; struct work_struct flip_work;
@ -630,6 +632,7 @@ static void page_flip_worker(struct work_struct *work)
drm_modeset_lock(&crtc->mutex, NULL); drm_modeset_lock(&crtc->mutex, NULL);
spin_lock_irqsave(&dev->event_lock, flags); spin_lock_irqsave(&dev->event_lock, flags);
/* /*
* The page flip could have been cancelled while waiting for the GEM * The page flip could have been cancelled while waiting for the GEM
* async operation to complete. Don't queue the flip in that case. * async operation to complete. Don't queue the flip in that case.
@ -641,9 +644,11 @@ static void page_flip_worker(struct work_struct *work)
omap_crtc->flip_state = OMAP_PAGE_FLIP_IDLE; omap_crtc->flip_state = OMAP_PAGE_FLIP_IDLE;
queue_flip = false; queue_flip = false;
} }
spin_unlock_irqrestore(&dev->event_lock, flags);
fb = crtc->primary->fb; fb = omap_crtc->flip_fb;
omap_crtc->flip_fb = NULL;
spin_unlock_irqrestore(&dev->event_lock, flags);
if (queue_flip) { if (queue_flip) {
omap_plane_mode_set(crtc->primary, crtc, fb, omap_plane_mode_set(crtc->primary, crtc, fb,
@ -657,7 +662,7 @@ static void page_flip_worker(struct work_struct *work)
bo = omap_framebuffer_bo(fb, 0); bo = omap_framebuffer_bo(fb, 0);
drm_gem_object_unreference_unlocked(bo); drm_gem_object_unreference_unlocked(bo);
drm_framebuffer_unreference(crtc->primary->fb); drm_framebuffer_unreference(fb);
} }
static void page_flip_cb(void *arg) static void page_flip_cb(void *arg)
@ -692,10 +697,19 @@ static int omap_crtc_page_flip(struct drm_crtc *crtc,
return -EBUSY; return -EBUSY;
} }
/*
* Store a reference to the framebuffer queued for page flip in the CRTC
* private structure. We can't rely on crtc->primary->fb in the page
* flip worker, as a racing CRTC disable (due for instance to an
* explicit framebuffer deletion from userspace) would set that field to
* NULL before the worker gets a change to run.
*/
drm_framebuffer_reference(fb);
omap_crtc->flip_fb = fb;
omap_crtc->flip_event = event; omap_crtc->flip_event = event;
omap_crtc->flip_state = OMAP_PAGE_FLIP_WAIT; omap_crtc->flip_state = OMAP_PAGE_FLIP_WAIT;
primary->fb = fb; primary->fb = fb;
drm_framebuffer_reference(fb);
spin_unlock_irqrestore(&dev->event_lock, flags); spin_unlock_irqrestore(&dev->event_lock, flags);