Re: [PATCH 05/10] drm/i915: skip DRM_I915_LOW_LEVEL_TRACEPOINTS with NOTRACE

[Sebastian Andrzej Siewior <bigeasy@linutronix.de>]

On 2024-04-08 13:06:50 [-0400], Steven Rostedt wrote:
> On Fri,  5 Apr 2024 16:18:23 +0200
> Sebastian Andrzej Siewior <bigeasy@linutronix.de> wrote:
> 
> > The order of the header files is important. If this header file is
> > included after tracepoint.h was included then the NOTRACE here becomes a
> > nop. Currently this happens for two .c files which use the tracepoitns
> > behind DRM_I915_LOW_LEVEL_TRACEPOINTS.
> 
> The NOTRACE should not be included in the individual trace files.
> 
> Can you show where this is an issue. I think this is fixing the symptom
> and not the bug itself.

The previous patch in the series disables trace points. I just checked
the difference with and without this one and there is none. I still have
| # ls -1 /sys/kernel/debug/tracing/events/i915/
|  enable
|  filter
|  g4x_wm
|  intel_cpu_fifo_underrun
|  intel_crtc_vblank_work_end
|  intel_crtc_vblank_work_start
|  intel_fbc_activate
|  intel_fbc_deactivate
|  intel_fbc_nuke
|  intel_frontbuffer_flush
|  intel_frontbuffer_invalidate
|  intel_memory_cxsr
|  intel_pch_fifo_underrun
|  intel_pipe_crc
|  intel_pipe_disable
|  intel_pipe_enable
|  intel_pipe_update_end
|  intel_pipe_update_start
|  intel_pipe_update_vblank_evaded
|  intel_plane_disable_arm
|  intel_plane_update_arm
|  intel_plane_update_noarm
|  vlv_fifo_size
|  vlv_wm

and I *think* there were none. This then leads to
| BUG: sleeping function called from invalid context at kernel/locking/spinlock_rt.c:48
| in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 794, name: Xorg
| preempt_count: 2, expected: 0
| RCU nest depth: 0, expected: 0
| 3 locks held by Xorg/794:
|  #0: ffffa49201d73c50 (crtc_ww_class_acquire){+.+.}-{0:0}, at: drm_mode_cursor_common+0xdf/0x250 [drm]
|  #1: ffff89ef11c46080 (crtc_ww_class_mutex){+.+.}-{3:3}, at: modeset_lock+0x68/0x1d0 [drm]
|  #2: ffff89ef2224ac70 (&uncore->lock){+.+.}-{2:2}, at: fwtable_read32+0x4d/0x280 [i915]
| Preemption disabled at:
| [<0000000000000000>] 0x0
| CPU: 3 PID: 794 Comm: Xorg Tainted: G        W          6.9.0-rc3-rt1+ #15
| Hardware name: To Be Filled By O.E.M. To Be Filled By O.E.M./Z68 Pro3-M, BIOS P2.10 04/24/2012
| Call Trace:
|  <TASK>
|  dump_stack_lvl+0x8d/0xb0
|  __might_resched+0x1a3/0x260
|  rt_spin_lock+0x48/0x100
|  fwtable_read32+0x4d/0x280 [i915]
|  trace_event_raw_event_intel_pipe_update_start+0xeb/0x1d0 [i915]
   ^^
|  intel_pipe_update_start+0x182/0x2f0 [i915]
|  intel_update_crtc+0x3f/0x400 [i915]
|  intel_commit_modeset_enables+0xab/0xd0 [i915]
|  intel_atomic_commit_tail+0x764/0x10b0 [i915]
|  intel_atomic_commit+0x318/0x360 [i915]
|  drm_atomic_commit+0x9e/0xd0 [drm]
|  drm_atomic_helper_disable_plane+0x87/0xe0 [drm_kms_helper]
|  drm_mode_cursor_universal+0x114/0x270 [drm]
|  drm_mode_cursor_common+0x11d/0x250 [drm]
|  drm_mode_cursor_ioctl+0x4b/0x70 [drm]
|  drm_ioctl_kernel+0xb4/0x110 [drm]
|  drm_ioctl+0x27b/0x4d0 [drm]

among a few other things I was not aware of.
So yes, this patch is not needed since it makes no difference but I still
have trace points I would rather not have.
If you a clue how to deal with this properly, I am all yours.

> -- Steve

Sebastian