On Fri, Mar 16, 2018 at 04:01:21PM +0100, Maarten Lankhorst wrote: > 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@xxxxxxxxxxxxxxx> > Cc: Paulo Zanoni <paulo.r.zanoni@xxxxxxxxx> > Cc: Rodrigo Vivi <rodrigo.vivi@xxxxxxxxx> Overall I'm not comfortable with removing the locks on fbc activate so I would deffer this to Paulo. Also my own experience with atomic variables and vblank counters weren't very positive on psr+dmc case. I always end up finding a corner case :( anyways few dummy questions below... > 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; Why FBC is so tied with vblanks? > 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; should we use something more descriptive here like vbl_counter instead of "vbl" variable right before "vblank" one. > > 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 why not a simple wait 1 vblank below? > * > - * 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 > > _______________________________________________ > Intel-gfx mailing list > Intel-gfx@xxxxxxxxxxxxxxxxxxxxx > https://lists.freedesktop.org/mailman/listinfo/intel-gfx _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/intel-gfx
