On 3/6/26 09:37, Michele Palazzi wrote:
Your new patch is an approach i already tried, and in my previous
testing i still had flip timeouts, so while i think separating the
cursor events makes sense and is correct, the root cause could be
different from what i initially assumed and sending the cursor events
immediately was masking it by relieving pressure.
Leo i finally reproduced with a bpftrace that tracks event ARM (flip vs
cursor) and DELIVER using kprobe offsets into the inlined prepare_flip_isr.
The hung commit is a cursor-only update on CRTC 0:
31088420 dm_pflip_high_irq [tid=0]
31088420 DELIVER event=ffff8b519225c580 crtc=0 [tid=0]
31088420 WAIT_FLIP EXIT 2ms [tid=203071]
31088421 ARM flip event=ffff8b4f26184c00 acrtc=ffff8b4ed1ddd000
[tid=203071]
31088421 commit_hw_done [tid=203071]
31088421 WAIT_FLIP ENTER [tid=203071]
31088422 dm_pflip_high_irq [tid=0]
31088422 DELIVER event=ffff8b4f26184c00 crtc=1 [tid=0]
31088422 WAIT_FLIP EXIT 1ms [tid=203071]
31088425 ARM cursor event=ffff8b519225ce00 acrtc=ffff8b4ed1dde000
[tid=203071]
31088425 commit_hw_done [tid=203071]
31088425 WAIT_FLIP ENTER [tid=203071]
31088428 ARM flip event=ffff8b4f26184480 acrtc=ffff8b4ed1ddd000
[tid=208580]
31088428 commit_hw_done [tid=208580]
31088428 WAIT_FLIP ENTER [tid=208580]
31088429 dm_pflip_high_irq [tid=0]
31088429 DELIVER event=ffff8b4f26184480 crtc=1 [tid=0]
31088429 WAIT_FLIP EXIT 1ms [tid=208580]
...
10036ms silence for tid=203071
no dm_pflip_high_irq, no DELIVER, no
drm_vblank_disable_and_save on CRTC 0
CRTC 1 continues normally throughout
...
31098462 WAIT_FLIP !!!TIMEOUT!!! waited 10036ms [tid=203071]
acrtc ffff8b4ed1dde000 = CRTC 0 (confirmed from ARM+DELIVER correlation)
acrtc ffff8b4ed1ddd000 = CRTC 1
Event ffff8b519225ce00 was armed as cursor on CRTC 0 and never
delivered. No dm_pflip_high_irq fired for CRTC 0 during the entire 10s
wait, and vblank was not disabled (no drm_vblank_disable_and_save in
that window). CRTC 1 kept flowing normally throughout.
The complete bpftrace is here https://pastebin.com/Xiju44Cy
Note that i did this on tag v6.19
