94 lines
3.1 KiB
Diff
94 lines
3.1 KiB
Diff
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From d7f32f81cf7579ac7d13127db88e789ea864824c Mon Sep 17 00:00:00 2001
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From: Derek Foreman <derekf@osg.samsung.com>
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Date: Thu, 24 Nov 2016 12:11:55 -0600
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Subject: [PATCH] drm/vc4: Fix race between page flip completion event and
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clean-up
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There was a small window where a userspace program could submit
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a pageflip after receiving a pageflip completion event yet still
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receive EBUSY.
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Signed-off-by: Derek Foreman <derekf@osg.samsung.com>
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Signed-off-by: Eric Anholt <eric@anholt.net>
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Reviewed-by: Eric Anholt <eric@anholt.net>
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Reviewed-by: Daniel Stone <daniels@collabora.com>
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(cherry picked from commit 26fc78f6fef39b9d7a15def5e7e9826ff68303f4)
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---
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drivers/gpu/drm/vc4/vc4_crtc.c | 8 ++++++++
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drivers/gpu/drm/vc4/vc4_drv.h | 1 +
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drivers/gpu/drm/vc4/vc4_kms.c | 33 +++++++++++++++++++++++++--------
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3 files changed, 34 insertions(+), 8 deletions(-)
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--- a/drivers/gpu/drm/vc4/vc4_crtc.c
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+++ b/drivers/gpu/drm/vc4/vc4_crtc.c
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@@ -682,6 +682,14 @@ void vc4_disable_vblank(struct drm_devic
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CRTC_WRITE(PV_INTEN, 0);
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}
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+/* Must be called with the event lock held */
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+bool vc4_event_pending(struct drm_crtc *crtc)
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+{
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+ struct vc4_crtc *vc4_crtc = to_vc4_crtc(crtc);
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+
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+ return !!vc4_crtc->event;
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+}
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+
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static void vc4_crtc_handle_page_flip(struct vc4_crtc *vc4_crtc)
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{
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struct drm_crtc *crtc = &vc4_crtc->base;
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--- a/drivers/gpu/drm/vc4/vc4_drv.h
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+++ b/drivers/gpu/drm/vc4/vc4_drv.h
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@@ -445,6 +445,7 @@ int vc4_bo_stats_debugfs(struct seq_file
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extern struct platform_driver vc4_crtc_driver;
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int vc4_enable_vblank(struct drm_device *dev, unsigned int crtc_id);
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void vc4_disable_vblank(struct drm_device *dev, unsigned int crtc_id);
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+bool vc4_event_pending(struct drm_crtc *crtc);
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int vc4_crtc_debugfs_regs(struct seq_file *m, void *arg);
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int vc4_crtc_get_scanoutpos(struct drm_device *dev, unsigned int crtc_id,
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unsigned int flags, int *vpos, int *hpos,
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--- a/drivers/gpu/drm/vc4/vc4_kms.c
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+++ b/drivers/gpu/drm/vc4/vc4_kms.c
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@@ -119,17 +119,34 @@ static int vc4_atomic_commit(struct drm_
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/* Make sure that any outstanding modesets have finished. */
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if (nonblock) {
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- ret = down_trylock(&vc4->async_modeset);
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- if (ret) {
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+ struct drm_crtc *crtc;
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+ struct drm_crtc_state *crtc_state;
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+ unsigned long flags;
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+ bool busy = false;
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+
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+ /*
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+ * If there's an undispatched event to send then we're
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+ * obviously still busy. If there isn't, then we can
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+ * unconditionally wait for the semaphore because it
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+ * shouldn't be contended (for long).
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+ *
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+ * This is to prevent a race where queuing a new flip
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+ * from userspace immediately on receipt of an event
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+ * beats our clean-up and returns EBUSY.
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+ */
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+ spin_lock_irqsave(&dev->event_lock, flags);
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+ for_each_crtc_in_state(state, crtc, crtc_state, i)
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+ busy |= vc4_event_pending(crtc);
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+ spin_unlock_irqrestore(&dev->event_lock, flags);
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+ if (busy) {
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kfree(c);
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return -EBUSY;
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}
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- } else {
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- ret = down_interruptible(&vc4->async_modeset);
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- if (ret) {
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- kfree(c);
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- return ret;
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- }
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+ }
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+ ret = down_interruptible(&vc4->async_modeset);
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+ if (ret) {
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+ kfree(c);
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+ return ret;
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}
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ret = drm_atomic_helper_prepare_planes(dev, state);
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