Arkham City dies of SIGSEGV about 140ms after the game writes PS3Progress_Frame_1,
on both the Qualcomm driver and Turnip, with the database on or off, Multithreaded
RSX on or off, and the RSX profiler on or off. A table of ten runs showed no setting
correlates with it.
The reason it took so long to even establish that it WAS a segfault: nothing records
it. No tombstone (/data/tombstones is root-only, so its emptiness proves nothing), no
logcat crash-buffer entry, and no line from our own handler. The single witness
anywhere is Zygote:
I Zygote : Process <pid> exited due to signal 11 (Segmentation fault)
That combination is what a stack overflow looks like here. The handler is installed
with SA_SIGINFO alone, so it runs on the faulting thread's own stack; if that stack is
what overflowed there is nowhere to run, it faults again immediately, and the kernel
applies the default action having written nothing.
So: an alternate signal stack per thread in thread_base::initialize, and SA_ONSTACK on
the handler. Thread-local rather than shared, because two threads can fault at once and
a shared stack would corrupt whichever report lost the race.
This does not fix the fault. It makes the fault reportable, which is the thing that has
been missing all along: the next occurrence should log where it came from instead of
vanishing. Android only.
RSX and every SPU thread shared one affinity mask, so on a 4+3+1 phone that is
six hot threads over five cores. RSX is the thread the frame waits on, and it
was measured spending about 10ms per frame inside its own loop without running:
not blocked on the GPU, not faulting, just waiting for a core.
Carves the single fastest core out of the SPU mask and leaves it in the RSX one.
RSX keeps the whole fast cluster and only loses the contention for the best
core; the SPUs lose one core out of several. Skipped when it would leave the
SPUs with a single core, which would be worse than the problem.
Only takes effect under the alternative scheduler. On Operating System mode
Android places threads itself and this code does not run.
set_native_priority used pthread_setschedparam with sched_priority. Android
threads run under SCHED_OTHER, where sched_priority must be zero and
sched_get_priority_max returns zero, so the call succeeded and changed nothing.
The RSX thread asks for a boost when it starts and was still measured at nice 0,
taking about 5300 involuntary preemptions a second, roughly 130 per frame, from
the PPU, SPU and audio threads sharing its cores. It is the thread everything
else waits on.
Under SCHED_OTHER the scheduler weights by nice, which setpriority does set, and
Android gives apps enough RLIMIT_NICE headroom to go negative for their own
threads. Applies -8 for a raise and +8 for a drop, and warns rather than fails
if the headroom is not there.
Modest on purpose: a hint to be scheduled ahead of the other emulator threads,
not a bid to starve them.
Adds an Android build of the RPCS3 core plus a Compose UI, and fixes several
things that stopped it working on ARM64.
Renderer:
- Emit concrete bounds for runtime sized arrays in uniform blocks when
VK_EXT_shader_uniform_buffer_unsized_array is missing. Adreno does not have
the extension, so every game pipeline failed with VK_ERROR_UNKNOWN and only
overlays drew.
- Probe and request that extension properly instead of chaining its feature
struct unconditionally.
- Hand VMA the Vulkan function pointers it needs under VK_NO_PROTOTYPES.
- Rebuild the surface and swapchain when the window is lost instead of killing
the RSX thread.
- Only create a GLES context when the GL renderer is actually selected.
SPU:
- Sum instead of taking an absolute difference in the ARM64 block verification
checksum. The difference collides on the near identical job binaries an SPU
job manager streams through one local store address, so a cached block could
run against another job's code.
Threading:
- Implement thread affinity on Android using sched_setaffinity.
- Add an ARM big.LITTLE core arrangement so SPU and RSX threads land on the
fast cores.
Misc:
- Detect the host CPU for the LLVM JIT instead of pinning cortex-a34.
- Fall back to the default audio device when cubeb cannot enumerate.
- Some SPU programs inexplicably fail to compile when TBL2/TBX2 are used.
- As an insane workaround, first try to compile with TBL2/TBX2, if LLVM crashes while compiling, try to compile the same program without TBL2/TBX2.
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