Two findings, the second only visible because of the first.
1. The harness has always had kernel logging switched off. log_mask DISABLES
categories (Kernel=1, Apu=2, Cpu=4, Gpu=8), so the long-standing --log_mask=13
meant Kernel+Cpu+Gpu off; kernel calls also log at Debug while log_level
defaults to Info. Seeing one needs BOTH LOG_MASK=12 and LOG_LEVEL=3, and no
boot log this project has taken ever contained a kernel call. boot_menu.sh now
takes LOG_MASK / LOG_LEVEL / EXTRA_FLAGS. A whole boot at Debug with Kernel on
is 23 MB, so the default was costing far more than it saved.
2. With that on, a captured failure shows the (A) handler doing everything right:
XamUserGetXUID(0, 7, ...)
NtCreateEvent(...)
ExCreateThread(..., entry=821748F0, ..., 00000001)
ExCreateThread Active: Thread Initially Suspended,
XThreadF80000CC (1F) Stack: 70880000-70900000
NtResumeThread(F80000CC, ...)
and the thread then never executing. Measured two independent ways: it makes
ZERO kernel calls - it appears 13 times in the log and every one is as an
ARGUMENT, never as the calling thread, while five other threads make 31905
calls after the resume - and its host thread has 00:00:00 CPU time while the
process sits at 546% and has burned 37 minutes of CPU in 6:46 wall.
A spinning thread burns CPU. This one has not run at all.
So the chain is: press delivered -> handler runs -> thread created suspended ->
resumed -> never scheduled. Input, the cache-flush crash and the game's own logic
are all excluded. A lost resume is a race, which is the first explanation that
fits the ~1-in-3 success rate.
Not settled: where the resume is lost, and no successful boot has been captured
with kernel logging to compare against.
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