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. [mlankhorst] The original patch was insufficient, and since the tracing infrastructure does not allow for partial disabling of tracepoints. Completely disable tracing for the entire i915 driver in PREEMPT_RT, a separate fix for display tracepoints on xe is added to make those work. Cc: Tvrtko Ursulin <tvrtko.ursu...@igalia.com> Reported-by: Luca Abeni <lucab...@gmail.com> Cc: Steven Rostedt <rost...@goodmis.org> Co-developed-by: Sebastian Andrzej Siewior <bige...@linutronix.de> Signed-off-by: Maarten Lankhorst <d...@lankhorst.se> --- drivers/gpu/drm/i915/Makefile | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/drivers/gpu/drm/i915/Makefile b/drivers/gpu/drm/i915/Makefile index 8535434430728..ba825d7f6ddf5 100644 --- a/drivers/gpu/drm/i915/Makefile +++ b/drivers/gpu/drm/i915/Makefile @@ -13,6 +13,11 @@ subdir-ccflags-$(CONFIG_DRM_I915_WERROR) += -Werror # drivers. Define I915 when building i915. subdir-ccflags-y += -DI915 +# Disable tracepoints on i915 for PREEMPT_RT, unfortunately +# it's an all or nothing flag. You cannot selectively disable +# only some tracepoints. +subdir-ccflags-$(CONFIG_PREEMPT_RT) += -DNOTRACE + subdir-ccflags-y += -I$(src) # Please keep these build lists sorted! -- 2.50.1
