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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>,
	Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
	Luca Abeni <lucabe72@gmail.com>,
	Steven Rostedt <rostedt@goodmis.org>
Subject: [PATCH 3/8] drm/i915: Disable tracing points on PREEMPT_RT
Date: Tue,  5 Oct 2021 17:00:41 +0200	[thread overview]
Message-ID: <20211005150046.1000285-4-bigeasy@linutronix.de> (raw)
In-Reply-To: <20211005150046.1000285-1-bigeasy@linutronix.de>

Luca Abeni reported this:
| BUG: scheduling while atomic: kworker/u8:2/15203/0x00000003
| CPU: 1 PID: 15203 Comm: kworker/u8:2 Not tainted 4.19.1-rt3 #10
| Call Trace:
|  rt_spin_lock+0x3f/0x50
|  gen6_read32+0x45/0x1d0 [i915]
|  g4x_get_vblank_counter+0x36/0x40 [i915]
|  trace_event_raw_event_i915_pipe_update_start+0x7d/0xf0 [i915]

The tracing events use trace_i915_pipe_update_start() among other events
use functions acquire spinlock_t locks which are transformed into
sleeping locks on PREEMPT_RT. A few trace points use
intel_get_crtc_scanline(), others use ->get_vblank_counter() wich also
might acquire a sleeping locks on PREEMPT_RT.
At the time the arguments are evaluated within trace point, preemption
is disabled and so the locks must not be acquired on PREEMPT_RT.

Based on this I don't see any other way than disable trace points on
PREMPT_RT.

Reported-by: Luca Abeni <lucabe72@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 drivers/gpu/drm/i915/i915_trace.h | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_trace.h b/drivers/gpu/drm/i915/i915_trace.h
index 806ad688274bf..773e7362c4442 100644
--- a/drivers/gpu/drm/i915/i915_trace.h
+++ b/drivers/gpu/drm/i915/i915_trace.h
@@ -2,6 +2,10 @@
 #if !defined(_I915_TRACE_H_) || defined(TRACE_HEADER_MULTI_READ)
 #define _I915_TRACE_H_
 
+#ifdef CONFIG_PREEMPT_RT
+#define NOTRACE
+#endif
+
 #include <linux/stringify.h>
 #include <linux/types.h>
 #include <linux/tracepoint.h>
-- 
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>,
	Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
	Luca Abeni <lucabe72@gmail.com>,
	Steven Rostedt <rostedt@goodmis.org>
Subject: [Intel-gfx] [PATCH 3/8] drm/i915: Disable tracing points on PREEMPT_RT
Date: Tue,  5 Oct 2021 17:00:41 +0200	[thread overview]
Message-ID: <20211005150046.1000285-4-bigeasy@linutronix.de> (raw)
In-Reply-To: <20211005150046.1000285-1-bigeasy@linutronix.de>

Luca Abeni reported this:
| BUG: scheduling while atomic: kworker/u8:2/15203/0x00000003
| CPU: 1 PID: 15203 Comm: kworker/u8:2 Not tainted 4.19.1-rt3 #10
| Call Trace:
|  rt_spin_lock+0x3f/0x50
|  gen6_read32+0x45/0x1d0 [i915]
|  g4x_get_vblank_counter+0x36/0x40 [i915]
|  trace_event_raw_event_i915_pipe_update_start+0x7d/0xf0 [i915]

The tracing events use trace_i915_pipe_update_start() among other events
use functions acquire spinlock_t locks which are transformed into
sleeping locks on PREEMPT_RT. A few trace points use
intel_get_crtc_scanline(), others use ->get_vblank_counter() wich also
might acquire a sleeping locks on PREEMPT_RT.
At the time the arguments are evaluated within trace point, preemption
is disabled and so the locks must not be acquired on PREEMPT_RT.

Based on this I don't see any other way than disable trace points on
PREMPT_RT.

Reported-by: Luca Abeni <lucabe72@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 drivers/gpu/drm/i915/i915_trace.h | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_trace.h b/drivers/gpu/drm/i915/i915_trace.h
index 806ad688274bf..773e7362c4442 100644
--- a/drivers/gpu/drm/i915/i915_trace.h
+++ b/drivers/gpu/drm/i915/i915_trace.h
@@ -2,6 +2,10 @@
 #if !defined(_I915_TRACE_H_) || defined(TRACE_HEADER_MULTI_READ)
 #define _I915_TRACE_H_
 
+#ifdef CONFIG_PREEMPT_RT
+#define NOTRACE
+#endif
+
 #include <linux/stringify.h>
 #include <linux/types.h>
 #include <linux/tracepoint.h>
-- 
2.33.0


  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 ` [PATCH 1/8] drm/i915: Use preempt_disable/enable_rt() where recommended Sebastian Andrzej Siewior
2021-10-05 15:00   ` [Intel-gfx] " 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 ` Sebastian Andrzej Siewior [this message]
2021-10-05 15:00   ` [Intel-gfx] [PATCH 3/8] drm/i915: Disable tracing points on PREEMPT_RT 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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