[klosixgaming-arch]

What

EA SPORTS FC 27 (PPSA34015) stopped once on Windows with:

terminate called after throwing an instance of 'std::system_error'
  what():  Joining guest thread: Access is denied
FATAL: abort() (SIGABRT)

The join comes from the title's thread wrapper (eboot 0x1d4b365, scePthreadJoin(handle, NULL) after its status poll). scePthreadJoin waits for _finished and then for the native handle. If another call releases the thread in the meantime, the join waits on a closed handle in freed memory. That other call is a scePthreadDetach, or a second scePthreadJoin whose ReleaseThread frees the thread. WaitForSingleObject then fails with ERROR_ACCESS_DENIED.

FreeBSD 11.4 libthr keeps a joiner field for this case (thr_join.c, thr_detach.c). This PR follows it, under _join_mtx:

• scePthreadDetach returns EINVAL while a thread waits to join the target.
• A second concurrent scePthreadJoin returns EOPNOTSUPP (ENOTSUP, 45), as join_common does.
• A join cancelled while it waits clears the joiner before it exits (backout_join).
• A join that completes sets _joined under the same lock, so a detach racing with its end returns EINVAL instead of releasing the thread a second time.

The libkernel debt entry for scePthreadJoin records this. main now has the _joined flag (second join after a completed one → ESRCH); this PR keeps it and adds the lock, so a detach cannot close the handle while a joiner waits.

Tested

• New guest_pthread_join_detach:
  • A detach while a joiner waits returns EINVAL.
  • A second joiner gets EOPNOTSUPP.
  • The first join completes with the return value.
  • Detach then join returns EINVAL.
• It passes on Linux (GCC 13.3, 20 consecutive runs) and on Windows 11 (WinLibs GCC 15.2.0). guest_pthread_start still passes on both.
• Rebased onto main 66702f1: guest_pthread_join_detach passes again on Windows 11. The Linux runs and guest_pthread_start above are from before the rebase.
• Not confirmed in the title. The stop above happened once. Since then PPSA34015 stops earlier in every run, at a pixel shader (v_readlane_b32 of lane 63 is outside the 32-lane host subgroup, see EA SPORTS FC 27 (PPSA34015) #6344), so I could not run it to the point of this race again. A run with this change and a log on the refused paths reached that earlier stop without the join error, which does not prove much either way.

Checklist

• Based on current main; no other open PR implements the same functions
• One topic per PR; follow-ups go in a new PR
• No comments in code except technical debt
• Unimplemented paths throw (NotImplemented_nid_no_patch); silent stubs are listed under Silent stubs in their library's technical debt file
• No notes, investigation .md files or images added to the repository (attach them to this PR)
• New third-party code is a submodule built from source
• Generic behaviour, not specific to one title
• Depends on: none
• Unblocks: PPSA34015 EA SPORTS FC 27 (PPSA34015) #6344
• GPUs tested: n/a
• AI-assisted: yes. Written with AI assistance and reviewed by me.

[github-actions]

Some comparisons could not be completed because a pull request conflicts with the base branch. Review these shared files manually before concluding that there is no overlap.

Pull request	Shared files not compared
PR 3986	core/libs/prx/libkernel/Pthread/src/Thread.cpp
PR 4972	core/libs/prx/libkernel/CMakeLists.txt
PR 5021	core/libs/prx/libkernel/CMakeLists.txt core/libs/prx/libkernel/Pthread/include/Pthread.hpp core/libs/prx/libkernel/Pthread/src/Thread.cpp docs/dev/debt/libkernel.md
PR 6044	core/libs/prx/libkernel/CMakeLists.txt
PR 6149	docs/dev/debt/libkernel.md
PR 6226	core/libs/prx/libkernel/CMakeLists.txt
PR 6446	docs/dev/debt/libkernel.md
PR 6510	docs/dev/debt/libkernel.md
PR 6519	docs/dev/debt/libkernel.md
PR 6534	core/libs/prx/libkernel/Pthread/include/Pthread.hpp core/libs/prx/libkernel/Pthread/src/Thread.cpp docs/dev/debt/libkernel.md
PR 6879	core/libs/prx/libkernel/Pthread/src/Thread.cpp
PR 6908	core/libs/prx/libkernel/CMakeLists.txt docs/dev/debt/libkernel.md
PR 6936	core/libs/prx/libkernel/CMakeLists.txt docs/dev/debt/libkernel.md
PR 6942	core/libs/prx/libkernel/CMakeLists.txt
PR 6977	core/libs/prx/libkernel/CMakeLists.txt docs/dev/debt/libkernel.md
PR 7039	docs/dev/debt/libkernel.md
PR 7049	docs/dev/debt/libkernel.md
PR 7075	docs/dev/debt/libkernel.md
PR 7088	docs/dev/debt/libkernel.md
PR 7105	docs/dev/debt/libkernel.md
PR 7121	docs/dev/debt/libkernel.md
PR 7129	core/libs/prx/libkernel/CMakeLists.txt docs/dev/debt/libkernel.md
PR 7149	core/libs/prx/libkernel/Pthread/include/Pthread.hpp core/libs/prx/libkernel/Pthread/src/Thread.cpp docs/dev/debt/libkernel.md
PR 7192	core/libs/prx/libkernel/CMakeLists.txt docs/dev/debt/libkernel.md
PR 7201	core/libs/prx/libkernel/CMakeLists.txt core/libs/prx/libkernel/Pthread/src/Thread.cpp
PR 7332	core/libs/prx/libkernel/CMakeLists.txt core/libs/prx/libkernel/Pthread/include/Pthread.hpp core/libs/prx/libkernel/Pthread/src/Thread.cpp docs/dev/debt/libkernel.md
PR 7450	core/libs/prx/libkernel/CMakeLists.txt
PR 7509	docs/dev/debt/libkernel.md
PR 7565	core/libs/prx/libkernel/Pthread/src/Thread.cpp docs/dev/debt/libkernel.md
PR 7653	docs/dev/debt/libkernel.md

[klosixgaming-arch]

No dependency: this PR builds on neither of them.

• fix(libkernel): answer a second scePthreadJoin with ESRCH #4481 makes a second join, after a completed one, return ESRCH. It does that by keeping the joined thread alive and checking _joined.
• fix(libkernel): answer pthread_getname_np for a joined thread with ESRCH #4533 makes pthread_getname_np on a joined thread return ESRCH, on top of the same _joined state.
• This PR covers a join or detach that runs while another join is waiting. It applies FreeBSD's joiner rule under _join_mtx.

They edit the same lines in scePthreadJoin and scePthreadDetach, so whichever merges second needs a small rebase. If #4481 lands first, its _joined early return can sit before the _join_mtx block here unchanged. The remaining PRs in the list are the AOT stack and CMake-only overlaps.

[blawesom]

Rebase handoff, with one contract repair — rebased onto current main (authorship unchanged). The conflicts were main's newer atomic thread state (std::atomic<bool> _joined, _handleStorage) meeting this PR's mutex-guarded _joining flag: the merged version keeps main's atomics plus your _joining flag under _join_mtx, and the detach check is the union (detached, joining, or already joined).

The repair: your join completion set _detached = true, which made a second scePthreadJoin return EINVAL where main's guest_pthread_second_join requires ESRCH. The join no longer marks the thread detached — the detach-after-join refusal your change is after is already covered by the _joined atomic in the detach path, and that test passes.

Verified on Linux (CachyOS, kernel 7.2.9, GCC 16.2.1, Ninja, Release, BUILD_TESTING=ON, AMD RX 9070 XT / RADV):

• builds; tools/check_conventions.py --base origin/main passes
• full suite: green apart from the known main regression (agc_driver_tessellation segfault, feat(shader): read hull inputs at a control-point index computed from data #4727), not this PR

To pick it up:

git fetch https://github.com/blawesom/AnyPS5 rebase/6487
git checkout <your branch>
git merge --ff-only FETCH_HEAD

Head is 785ae9120.