From: Sebastian Andrzej Siewior <bigeasy@linutronix.de> To: intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org Cc: Jani Nikula <jani.nikula@linux.intel.com>, Joonas Lahtinen <joonas.lahtinen@linux.intel.com>, Rodrigo Vivi <rodrigo.vivi@intel.com>, David Airlie <airlied@linux.ie>, Daniel Vetter <daniel@ffwll.ch>, Thomas Gleixner <tglx@linutronix.de>, Mike Galbraith <umgwanakikbuti@gmail.com>, Mario Kleiner <mario.kleiner.de@gmail.com>, Sebastian Andrzej Siewior <bigeasy@linutronix.de> Subject: [PATCH 1/8] drm/i915: Use preempt_disable/enable_rt() where recommended Date: Tue, 5 Oct 2021 17:00:39 +0200 [thread overview] Message-ID: <20211005150046.1000285-2-bigeasy@linutronix.de> (raw) In-Reply-To: <20211005150046.1000285-1-bigeasy@linutronix.de> From: Mike Galbraith <umgwanakikbuti@gmail.com> Mario Kleiner suggest in commit ad3543ede630f ("drm/intel: Push get_scanout_position() timestamping into kms driver.") a spots where preemption should be disabled on PREEMPT_RT. The difference is that on PREEMPT_RT the intel_uncore::lock disables neither preemption nor interrupts and so region remains preemptible. The area covers only register reads and writes. The part that worries me is: - __intel_get_crtc_scanline() the worst case is 100us if no match is found. - intel_crtc_scanlines_since_frame_timestamp() not sure how long this may take in the worst case. It was in the RT queue for a while and nobody complained. Disable preemption on PREEPMPT_RT during timestamping. [bigeasy: patch description.] Cc: Mario Kleiner <mario.kleiner.de@gmail.com> Signed-off-by: Mike Galbraith <umgwanakikbuti@gmail.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> --- drivers/gpu/drm/i915/i915_irq.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c index 9bc4f4a8e12ec..547347241a47c 100644 --- a/drivers/gpu/drm/i915/i915_irq.c +++ b/drivers/gpu/drm/i915/i915_irq.c @@ -886,7 +886,8 @@ static bool i915_get_crtc_scanoutpos(struct drm_crtc *_crtc, */ spin_lock_irqsave(&dev_priv->uncore.lock, irqflags); - /* preempt_disable_rt() should go right here in PREEMPT_RT patchset. */ + if (IS_ENABLED(CONFIG_PREEMPT_RT)) + preempt_disable(); /* Get optional system timestamp before query. */ if (stime) @@ -950,7 +951,8 @@ static bool i915_get_crtc_scanoutpos(struct drm_crtc *_crtc, if (etime) *etime = ktime_get(); - /* preempt_enable_rt() should go right here in PREEMPT_RT patchset. */ + if (IS_ENABLED(CONFIG_PREEMPT_RT)) + preempt_enable(); spin_unlock_irqrestore(&dev_priv->uncore.lock, irqflags); -- 2.33.0
WARNING: multiple messages have this Message-ID (diff)
From: Sebastian Andrzej Siewior <bigeasy@linutronix.de> To: intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org Cc: Jani Nikula <jani.nikula@linux.intel.com>, Joonas Lahtinen <joonas.lahtinen@linux.intel.com>, Rodrigo Vivi <rodrigo.vivi@intel.com>, David Airlie <airlied@linux.ie>, Daniel Vetter <daniel@ffwll.ch>, Thomas Gleixner <tglx@linutronix.de>, Mike Galbraith <umgwanakikbuti@gmail.com>, Mario Kleiner <mario.kleiner.de@gmail.com>, Sebastian Andrzej Siewior <bigeasy@linutronix.de> Subject: [Intel-gfx] [PATCH 1/8] drm/i915: Use preempt_disable/enable_rt() where recommended Date: Tue, 5 Oct 2021 17:00:39 +0200 [thread overview] Message-ID: <20211005150046.1000285-2-bigeasy@linutronix.de> (raw) In-Reply-To: <20211005150046.1000285-1-bigeasy@linutronix.de> From: Mike Galbraith <umgwanakikbuti@gmail.com> Mario Kleiner suggest in commit ad3543ede630f ("drm/intel: Push get_scanout_position() timestamping into kms driver.") a spots where preemption should be disabled on PREEMPT_RT. The difference is that on PREEMPT_RT the intel_uncore::lock disables neither preemption nor interrupts and so region remains preemptible. The area covers only register reads and writes. The part that worries me is: - __intel_get_crtc_scanline() the worst case is 100us if no match is found. - intel_crtc_scanlines_since_frame_timestamp() not sure how long this may take in the worst case. It was in the RT queue for a while and nobody complained. Disable preemption on PREEPMPT_RT during timestamping. [bigeasy: patch description.] Cc: Mario Kleiner <mario.kleiner.de@gmail.com> Signed-off-by: Mike Galbraith <umgwanakikbuti@gmail.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> --- drivers/gpu/drm/i915/i915_irq.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c index 9bc4f4a8e12ec..547347241a47c 100644 --- a/drivers/gpu/drm/i915/i915_irq.c +++ b/drivers/gpu/drm/i915/i915_irq.c @@ -886,7 +886,8 @@ static bool i915_get_crtc_scanoutpos(struct drm_crtc *_crtc, */ spin_lock_irqsave(&dev_priv->uncore.lock, irqflags); - /* preempt_disable_rt() should go right here in PREEMPT_RT patchset. */ + if (IS_ENABLED(CONFIG_PREEMPT_RT)) + preempt_disable(); /* Get optional system timestamp before query. */ if (stime) @@ -950,7 +951,8 @@ static bool i915_get_crtc_scanoutpos(struct drm_crtc *_crtc, if (etime) *etime = ktime_get(); - /* preempt_enable_rt() should go right here in PREEMPT_RT patchset. */ + if (IS_ENABLED(CONFIG_PREEMPT_RT)) + preempt_enable(); spin_unlock_irqrestore(&dev_priv->uncore.lock, irqflags); -- 2.33.0
next prev parent reply other threads:[~2021-10-05 15:01 UTC|newest] Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top 2021-10-05 15:00 [PATCH 0/8] drm/i915: PREEMPT_RT related fixups Sebastian Andrzej Siewior 2021-10-05 15:00 ` [Intel-gfx] " Sebastian Andrzej Siewior 2021-10-05 15:00 ` Sebastian Andrzej Siewior [this message] 2021-10-05 15:00 ` [Intel-gfx] [PATCH 1/8] drm/i915: Use preempt_disable/enable_rt() where recommended Sebastian Andrzej Siewior 2021-10-05 15:00 ` [PATCH 2/8] drm/i915: Don't disable interrupts on PREEMPT_RT during atomic updates Sebastian Andrzej Siewior 2021-10-05 15:00 ` [Intel-gfx] " Sebastian Andrzej Siewior 2021-10-06 9:16 ` Ville Syrjälä 2021-10-05 15:00 ` [PATCH 3/8] drm/i915: Disable tracing points on PREEMPT_RT Sebastian Andrzej Siewior 2021-10-05 15:00 ` [Intel-gfx] " Sebastian Andrzej Siewior 2021-10-06 9:34 ` Ville Syrjälä 2021-10-06 9:34 ` [Intel-gfx] " Ville Syrjälä 2021-10-06 10:15 ` Sebastian Andrzej Siewior 2021-10-06 10:15 ` [Intel-gfx] " Sebastian Andrzej Siewior 2021-10-06 16:46 ` Sebastian Andrzej Siewior 2021-10-06 16:46 ` [Intel-gfx] " Sebastian Andrzej Siewior 2021-10-05 15:00 ` [PATCH 4/8] drm/i915: skip DRM_I915_LOW_LEVEL_TRACEPOINTS with NOTRACE Sebastian Andrzej Siewior 2021-10-05 15:00 ` [Intel-gfx] " Sebastian Andrzej Siewior 2021-10-05 15:00 ` [PATCH 5/8] drm/i915/gt: Queue and wait for the irq_work item Sebastian Andrzej Siewior 2021-10-05 15:00 ` [Intel-gfx] " Sebastian Andrzej Siewior 2021-10-05 15:00 ` [PATCH 6/8] drm/i915/gt: Use spin_lock_irq() instead of local_irq_disable() + spin_lock() Sebastian Andrzej Siewior 2021-10-05 15:00 ` [Intel-gfx] " Sebastian Andrzej Siewior 2021-10-05 15:00 ` [PATCH 7/8] drm/i915: Drop the irqs_disabled() check Sebastian Andrzej Siewior 2021-10-05 15:00 ` [Intel-gfx] " Sebastian Andrzej Siewior 2021-10-05 15:00 ` [PATCH 8/8] drm/i915: Don't disable interrupts and pretend a lock as been acquired in __timeline_mark_lock() Sebastian Andrzej Siewior 2021-10-05 15:00 ` [Intel-gfx] " Sebastian Andrzej Siewior 2021-10-05 19:16 ` Peter Zijlstra 2021-10-05 19:16 ` [Intel-gfx] " Peter Zijlstra 2021-10-06 6:58 ` Sebastian Andrzej Siewior 2021-10-06 6:58 ` [Intel-gfx] " Sebastian Andrzej Siewior 2021-10-08 6:21 ` [drm/i915] 511e5fb0c3: WARNING:suspicious_RCU_usage kernel test robot 2021-10-08 6:21 ` kernel test robot 2021-10-08 6:21 ` [Intel-gfx] " kernel test robot 2021-10-05 16:12 ` [Intel-gfx] ✗ Fi.CI.CHECKPATCH: warning for drm/i915: PREEMPT_RT related fixups Patchwork 2021-10-05 16:48 ` [Intel-gfx] ✗ Fi.CI.BAT: failure " Patchwork 2021-10-06 17:41 ` [Intel-gfx] ✗ Fi.CI.BUILD: failure for drm/i915: PREEMPT_RT related fixups. (rev2) Patchwork
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