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[SRU,S,3/9] UBUNTU: SAUCE: drm/i915: Disable tracing points on PREEMPT_RT

Message ID 20260924122708.1076074-4-benjamin.wheeler@canonical.com
State New
Headers show
Series Add drm/i915 PREEMPT_RT support | expand

Commit Message

Benjamin Wheeler Sept. 24, 2026, 12:27 p.m. UTC 
From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

BugLink: https://bugs.launchpad.net/bugs/2168432

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_intel_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.

Acked-by: Tvrtko Ursulin <tvrtko.ursulin@igalia.com>
Reported-by: Luca Abeni <lucabe72@gmail.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Benjamin Wheeler <benjamin.wheeler@canonical.com>
---
 drivers/gpu/drm/i915/display/intel_display_trace.h | 4 ++++
 drivers/gpu/drm/i915/i915_trace.h                  | 4 ++++
 drivers/gpu/drm/i915/intel_uncore_trace.h          | 4 ++++
 3 files changed, 12 insertions(+)
diff mbox series

Patch

diff --git a/drivers/gpu/drm/i915/display/intel_display_trace.h b/drivers/gpu/drm/i915/display/intel_display_trace.h
index 504d105935bc..a974fedc9692 100644
--- a/drivers/gpu/drm/i915/display/intel_display_trace.h
+++ b/drivers/gpu/drm/i915/display/intel_display_trace.h
@@ -13,6 +13,10 @@ 
 #if !defined(__INTEL_DISPLAY_TRACE_H__) || defined(TRACE_HEADER_MULTI_READ)
 #define __INTEL_DISPLAY_TRACE_H__
 
+#if defined(CONFIG_PREEMPT_RT) && !defined(NOTRACE)
+#define NOTRACE
+#endif
+
 #include <linux/string.h>
 #include <linux/string_helpers.h>
 #include <linux/types.h>
diff --git a/drivers/gpu/drm/i915/i915_trace.h b/drivers/gpu/drm/i915/i915_trace.h
index 7ed41ce9b708..6b87ef6005c6 100644
--- a/drivers/gpu/drm/i915/i915_trace.h
+++ b/drivers/gpu/drm/i915/i915_trace.h
@@ -6,6 +6,10 @@ 
 #if !defined(_I915_TRACE_H_) || defined(TRACE_HEADER_MULTI_READ)
 #define _I915_TRACE_H_
 
+#if defined(CONFIG_PREEMPT_RT) && !defined(NOTRACE)
+#define NOTRACE
+#endif
+
 #include <linux/stringify.h>
 #include <linux/types.h>
 #include <linux/tracepoint.h>
diff --git a/drivers/gpu/drm/i915/intel_uncore_trace.h b/drivers/gpu/drm/i915/intel_uncore_trace.h
index f13ff71edf2d..3c67e267fb60 100644
--- a/drivers/gpu/drm/i915/intel_uncore_trace.h
+++ b/drivers/gpu/drm/i915/intel_uncore_trace.h
@@ -7,6 +7,10 @@ 
 #if !defined(__INTEL_UNCORE_TRACE_H__) || defined(TRACE_HEADER_MULTI_READ)
 #define __INTEL_UNCORE_TRACE_H__
 
+#if defined(CONFIG_PREEMPT_RT) && !defined(NOTRACE)
+#define NOTRACE
+#endif
+
 #include "i915_reg_defs.h"
 
 #include <linux/types.h>