[Intel-gfx] [PATCH] drm/i915: Rework FBC schedule locking
Maarten Lankhorst
maarten.lankhorst at linux.intel.com
Fri Mar 16 15:01:21 UTC 2018
Instead of taking fbc->lock inside the worker, don't take any lock
and cancel the work synchronously to prevent races. Since the worker
waits for a vblank before activating, wake up all vblank waiters after
signalling the cancel through unsetting work->scheduled_vblank. This
will make sure that we don't wait too long when cancelling the activation.
Signed-off-by: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
Cc: Paulo Zanoni <paulo.r.zanoni at intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi at intel.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=103167
---
drivers/gpu/drm/i915/i915_debugfs.c | 4 +-
drivers/gpu/drm/i915/i915_drv.h | 3 +-
drivers/gpu/drm/i915/intel_fbc.c | 76 ++++++++++++++++---------------------
3 files changed, 36 insertions(+), 47 deletions(-)
diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
index 98e169636f86..cbf5504de183 100644
--- a/drivers/gpu/drm/i915/i915_debugfs.c
+++ b/drivers/gpu/drm/i915/i915_debugfs.c
@@ -1643,9 +1643,9 @@ static int i915_fbc_status(struct seq_file *m, void *unused)
else
seq_printf(m, "FBC disabled: %s\n", fbc->no_fbc_reason);
- if (fbc->work.scheduled)
+ if (work_busy(&fbc->work.work))
seq_printf(m, "FBC worker scheduled on vblank %llu, now %llu\n",
- fbc->work.scheduled_vblank,
+ (u64)atomic64_read(&fbc->work.scheduled_vblank),
drm_crtc_vblank_count(&fbc->crtc->base));
if (intel_fbc_is_active(dev_priv)) {
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 9262cfb8aac2..a7a1b0453320 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -558,8 +558,7 @@ struct intel_fbc {
} params;
struct intel_fbc_work {
- bool scheduled;
- u64 scheduled_vblank;
+ atomic64_t scheduled_vblank;
struct work_struct work;
} work;
diff --git a/drivers/gpu/drm/i915/intel_fbc.c b/drivers/gpu/drm/i915/intel_fbc.c
index 707d49c12638..20d45bcb6b6b 100644
--- a/drivers/gpu/drm/i915/intel_fbc.c
+++ b/drivers/gpu/drm/i915/intel_fbc.c
@@ -357,10 +357,6 @@ static bool intel_fbc_hw_is_active(struct drm_i915_private *dev_priv)
static void intel_fbc_hw_activate(struct drm_i915_private *dev_priv)
{
- struct intel_fbc *fbc = &dev_priv->fbc;
-
- fbc->active = true;
-
if (INTEL_GEN(dev_priv) >= 7)
gen7_fbc_activate(dev_priv);
else if (INTEL_GEN(dev_priv) >= 5)
@@ -407,16 +403,13 @@ static void intel_fbc_work_fn(struct work_struct *__work)
struct intel_fbc_work *work = &fbc->work;
struct intel_crtc *crtc = fbc->crtc;
struct drm_vblank_crtc *vblank = &dev_priv->drm.vblank[crtc->pipe];
+ u64 vbl;
if (drm_crtc_vblank_get(&crtc->base)) {
/* CRTC is now off, leave FBC deactivated */
- mutex_lock(&fbc->lock);
- work->scheduled = false;
- mutex_unlock(&fbc->lock);
return;
}
-retry:
/* Delay the actual enabling to let pageflipping cease and the
* display to settle before starting the compression. Note that
* this delay also serves a second purpose: it allows for a
@@ -425,34 +418,35 @@ static void intel_fbc_work_fn(struct work_struct *__work)
*
* WaFbcWaitForVBlankBeforeEnable:ilk,snb
*
- * It is also worth mentioning that since work->scheduled_vblank can be
- * updated multiple times by the other threads, hitting the timeout is
- * not an error condition. We'll just end up hitting the "goto retry"
- * case below.
+ * This may be killed by unsetting scheduled_vblank, in which
+ * case we return early without activating.
*/
wait_event_timeout(vblank->queue,
- drm_crtc_vblank_count(&crtc->base) != work->scheduled_vblank,
+ !(vbl = atomic64_read(&work->scheduled_vblank)) || vbl != drm_crtc_vblank_count(&crtc->base),
msecs_to_jiffies(50));
- mutex_lock(&fbc->lock);
+ if (vbl)
+ intel_fbc_hw_activate(dev_priv);
- /* Were we cancelled? */
- if (!work->scheduled)
- goto out;
+ drm_crtc_vblank_put(&crtc->base);
+}
- /* Were we delayed again while this function was sleeping? */
- if (drm_crtc_vblank_count(&crtc->base) == work->scheduled_vblank) {
- mutex_unlock(&fbc->lock);
- goto retry;
- }
+static void intel_fbc_cancel_activation(struct drm_i915_private *dev_priv)
+{
+ struct intel_fbc *fbc = &dev_priv->fbc;
+ struct intel_crtc *crtc;
+ struct drm_vblank_crtc *vblank;
- intel_fbc_hw_activate(dev_priv);
+ if (!fbc->active)
+ return;
- work->scheduled = false;
+ crtc = fbc->crtc;
+ vblank = &dev_priv->drm.vblank[crtc->pipe];
-out:
- mutex_unlock(&fbc->lock);
- drm_crtc_vblank_put(&crtc->base);
+ /* Kill FBC worker if it's waiting */
+ atomic64_set(&fbc->work.scheduled_vblank, 0);
+ wake_up_all(&vblank->queue);
+ cancel_work_sync(&fbc->work.work);
}
static void intel_fbc_schedule_activation(struct intel_crtc *crtc)
@@ -471,12 +465,10 @@ static void intel_fbc_schedule_activation(struct intel_crtc *crtc)
return;
}
- /* It is useless to call intel_fbc_cancel_work() or cancel_work() in
- * this function since we're not releasing fbc.lock, so it won't have an
- * opportunity to grab it to discover that it was cancelled. So we just
- * update the expected jiffy count. */
- work->scheduled = true;
- work->scheduled_vblank = drm_crtc_vblank_count(&crtc->base);
+ intel_fbc_cancel_activation(dev_priv);
+ fbc->active = true;
+
+ atomic64_set(&work->scheduled_vblank, drm_crtc_accurate_vblank_count(&crtc->base));
drm_crtc_vblank_put(&crtc->base);
schedule_work(&work->work);
@@ -489,13 +481,11 @@ static void intel_fbc_deactivate(struct drm_i915_private *dev_priv,
WARN_ON(!mutex_is_locked(&fbc->lock));
- /* Calling cancel_work() here won't help due to the fact that the work
- * function grabs fbc->lock. Just set scheduled to false so the work
- * function can know it was cancelled. */
- fbc->work.scheduled = false;
+ if (fbc->active) {
+ intel_fbc_cancel_activation(dev_priv);
- if (fbc->active)
intel_fbc_hw_deactivate(dev_priv);
+ }
fbc->no_fbc_reason = reason;
}
@@ -1222,11 +1212,11 @@ void intel_fbc_disable(struct intel_crtc *crtc)
WARN_ON(crtc->active);
mutex_lock(&fbc->lock);
+ intel_fbc_cancel_activation(dev_priv);
+
if (fbc->crtc == crtc)
__intel_fbc_disable(dev_priv);
mutex_unlock(&fbc->lock);
-
- cancel_work_sync(&fbc->work.work);
}
/**
@@ -1243,13 +1233,13 @@ void intel_fbc_global_disable(struct drm_i915_private *dev_priv)
return;
mutex_lock(&fbc->lock);
+ intel_fbc_cancel_activation(dev_priv);
+
if (fbc->enabled) {
WARN_ON(fbc->crtc->active);
__intel_fbc_disable(dev_priv);
}
mutex_unlock(&fbc->lock);
-
- cancel_work_sync(&fbc->work.work);
}
static void intel_fbc_underrun_work_fn(struct work_struct *work)
@@ -1373,11 +1363,11 @@ void intel_fbc_init(struct drm_i915_private *dev_priv)
struct intel_fbc *fbc = &dev_priv->fbc;
INIT_WORK(&fbc->work.work, intel_fbc_work_fn);
+ atomic64_set(&fbc->work.scheduled_vblank, 0);
INIT_WORK(&fbc->underrun_work, intel_fbc_underrun_work_fn);
mutex_init(&fbc->lock);
fbc->enabled = false;
fbc->active = false;
- fbc->work.scheduled = false;
if (need_fbc_vtd_wa(dev_priv))
mkwrite_device_info(dev_priv)->has_fbc = false;
--
2.16.2
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