Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 26fc78f6 authored by Derek Foreman's avatar Derek Foreman Committed by Eric Anholt
Browse files

drm/vc4: Fix race between page flip completion event and clean-up 



There was a small window where a userspace program could submit
a pageflip after receiving a pageflip completion event yet still
receive EBUSY.

Signed-off-by: default avatarDerek Foreman <derekf@osg.samsung.com>
Signed-off-by: default avatarEric Anholt <eric@anholt.net>
Reviewed-by: default avatarEric Anholt <eric@anholt.net>
Reviewed-by: default avatarDaniel Stone <daniels@collabora.com>
parent c778cc5d

drivers/gpu/drm/vc4/vc4_crtc.c

+8 −0
Original line number Diff line number Diff line
@@ -669,6 +669,14 @@ void vc4_disable_vblank(struct drm_device *dev, unsigned int crtc_id) 
	CRTC_WRITE(PV_INTEN, 0);

}



/* Must be called with the event lock held */

bool vc4_event_pending(struct drm_crtc *crtc)

{

	struct vc4_crtc *vc4_crtc = to_vc4_crtc(crtc);



	return !!vc4_crtc->event;

}



static void vc4_crtc_handle_page_flip(struct vc4_crtc *vc4_crtc)

{

	struct drm_crtc *crtc = &vc4_crtc->base;

drivers/gpu/drm/vc4/vc4_drv.h

+1 −0
Original line number Diff line number Diff line
@@ -442,6 +442,7 @@ int vc4_bo_stats_debugfs(struct seq_file *m, void *arg); 
extern struct platform_driver vc4_crtc_driver;

int vc4_enable_vblank(struct drm_device *dev, unsigned int crtc_id);

void vc4_disable_vblank(struct drm_device *dev, unsigned int crtc_id);

bool vc4_event_pending(struct drm_crtc *crtc);

int vc4_crtc_debugfs_regs(struct seq_file *m, void *arg);

int vc4_crtc_get_scanoutpos(struct drm_device *dev, unsigned int crtc_id,

			    unsigned int flags, int *vpos, int *hpos,

drivers/gpu/drm/vc4/vc4_kms.c

+25 −8
Original line number Diff line number Diff line
@@ -119,18 +119,35 @@ static int vc4_atomic_commit(struct drm_device *dev, 


	/* Make sure that any outstanding modesets have finished. */

	if (nonblock) {

		ret = down_trylock(&vc4->async_modeset);

		if (ret) {

		struct drm_crtc *crtc;

		struct drm_crtc_state *crtc_state;

		unsigned long flags;

		bool busy = false;



		/*

		 * If there's an undispatched event to send then we're

		 * obviously still busy.  If there isn't, then we can

		 * unconditionally wait for the semaphore because it

		 * shouldn't be contended (for long).

		 *

		 * This is to prevent a race where queuing a new flip

		 * from userspace immediately on receipt of an event

		 * beats our clean-up and returns EBUSY.

		 */

		spin_lock_irqsave(&dev->event_lock, flags);

		for_each_crtc_in_state(state, crtc, crtc_state, i)

			busy |= vc4_event_pending(crtc);

		spin_unlock_irqrestore(&dev->event_lock, flags);

		if (busy) {

			kfree(c);

			return -EBUSY;

		}

	} else {

	}

	ret = down_interruptible(&vc4->async_modeset);

	if (ret) {

		kfree(c);

		return ret;

	}

	}



	ret = drm_atomic_helper_prepare_planes(dev, state);

	if (ret) {