From 4ebc7d7d4352df30647a5e2b32fd71fe3ddffcf2 Mon Sep 17 00:00:00 2001
From: milescoviello <kitslayer29@gmail.com>
Date: Sun, 18 Oct 2026 02:39:34 +0000
Subject: [PATCH] fix(libkernel): answer a join of the calling thread before
 its detach state

scePthreadJoin checked whether the thread was detached before whether it
was the calling thread. So a detached thread joining itself got EINVAL
instead of EDEADLK, and so did the main thread, which scePthreadSelf
adopts as detached. FreeBSD's join checks the calling thread right after
the null check and before it looks at the detach state. The self check
now comes first; the null, detached and already-joined answers are
unchanged.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
---
 .../libs/prx/libkernel/Pthread/src/Thread.cpp |  2 +-
 core/libs/tests/GuestPthreadJoinSelf.cpp      | 26 +++++++++++++++++++
 core/libs/tests/GuestThreadSelf.cpp           |  3 ++-
 3 files changed, 29 insertions(+), 2 deletions(-)

diff --git a/core/libs/prx/libkernel/Pthread/src/Thread.cpp b/core/libs/prx/libkernel/Pthread/src/Thread.cpp
index b27a79bb5e..cba281fd82 100644
--- a/core/libs/prx/libkernel/Pthread/src/Thread.cpp
+++ b/core/libs/prx/libkernel/Pthread/src/Thread.cpp
@@ -830,9 +830,9 @@ int APS5_VABI scePthreadCreate(Pthread* thread, const PthreadAttr* attr, Pthread
 
 int APS5_VABI scePthreadJoin(Pthread thread, void** retval) {
     if (!thread) return SCE_KERNEL_ERROR_EINVAL;
+    if (thread == CurrentGuestState().current) return SCE_KERNEL_ERROR_EDEADLK;
     if (thread->_detached) return SCE_KERNEL_ERROR_EINVAL;
     if (thread->_joined.load(std::memory_order_acquire)) return SCE_KERNEL_ERROR_ESRCH;
-    if (thread == CurrentGuestState().current) return SCE_KERNEL_ERROR_EDEADLK;
     ThreadCancel::Check();
     {
         std::unique_lock lock(thread->_join_mtx);
diff --git a/core/libs/tests/GuestPthreadJoinSelf.cpp b/core/libs/tests/GuestPthreadJoinSelf.cpp
index 742fa9d734..2fec26bef7 100644
--- a/core/libs/tests/GuestPthreadJoinSelf.cpp
+++ b/core/libs/tests/GuestPthreadJoinSelf.cpp
@@ -1,12 +1,16 @@
 #include "SceTypes.hpp"
+#include <atomic>
+#include <chrono>
 #include <cstdint>
 #include <cstdlib>
+#include <thread>
 
 extern "C" {
 int APS5_VABI scePthreadCreate(Pthread* thread, const PthreadAttr* attr, PthreadEntry entry, void* arg, const char* name);
 int APS5_VABI scePthreadJoin(Pthread thread, void** retval);
 Pthread APS5_VABI scePthreadSelf(void);
 int APS5_VABI pthread_join_nid_postfix(Pthread thread, void** retval);
+int APS5_VABI scePthreadDetach(Pthread thread);
 }
 
 static constexpr int SCE_OK = 0;
@@ -23,6 +27,18 @@ static void* APS5_VABI JoinSelf(void*) {
     return reinterpret_cast<void*>(std::uintptr_t{0x1234});
 }
 
+static std::atomic<int> detachedChecks{0};
+
+static void* APS5_VABI DetachThenJoinSelf(void*) {
+    void* result = reinterpret_cast<void*>(std::uintptr_t{0x66});
+    Require(scePthreadDetach(scePthreadSelf()) == SCE_OK);
+    Require(scePthreadJoin(scePthreadSelf(), &result) == SCE_KERNEL_ERROR_EDEADLK);
+    Require(pthread_join_nid_postfix(scePthreadSelf(), &result) == GUEST_EDEADLK);
+    Require(result == reinterpret_cast<void*>(std::uintptr_t{0x66}));
+    detachedChecks.store(1);
+    return nullptr;
+}
+
 int main() {
     Pthread thread = nullptr;
     void* result = nullptr;
@@ -36,4 +52,14 @@ int main() {
     Require(scePthreadCreate(&thread, &unset, JoinSelf, nullptr, "unset-attr") == SCE_OK);
     Require(scePthreadJoin(thread, &result) == SCE_OK);
     Require(result == reinterpret_cast<void*>(std::uintptr_t{0x1234}));
+
+    thread = nullptr;
+    Require(scePthreadCreate(&thread, nullptr, DetachThenJoinSelf, nullptr, "detach-join-self") == SCE_OK);
+    for (int wait = 0; wait < 5000 && detachedChecks.load() == 0; ++wait) std::this_thread::sleep_for(std::chrono::milliseconds(1));
+    Require(detachedChecks.load() == 1);
+
+    result = reinterpret_cast<void*>(std::uintptr_t{0x77});
+    Require(scePthreadJoin(scePthreadSelf(), &result) == SCE_KERNEL_ERROR_EDEADLK);
+    Require(pthread_join_nid_postfix(scePthreadSelf(), &result) == GUEST_EDEADLK);
+    Require(result == reinterpret_cast<void*>(std::uintptr_t{0x77}));
 }
diff --git a/core/libs/tests/GuestThreadSelf.cpp b/core/libs/tests/GuestThreadSelf.cpp
index 9c59471e91..c94f557187 100644
--- a/core/libs/tests/GuestThreadSelf.cpp
+++ b/core/libs/tests/GuestThreadSelf.cpp
@@ -110,7 +110,8 @@ int main() {
     Require(pthread_getthreadid_np_nid_postfix() == static_cast<int>(mainTid));
     int local = 0;
     Require(StackContains(mainSelf, &local));
-    Require(scePthreadJoin(mainSelf, nullptr) == SCE_KERNEL_ERROR_EINVAL);
+    Require(scePthreadJoin(mainSelf, nullptr) == SCE_KERNEL_ERROR_EDEADLK);
+    Require(pthread_join_nid_postfix(mainSelf, nullptr) == GUEST_EDEADLK);
     Require(scePthreadDetach(mainSelf) == SCE_KERNEL_ERROR_EINVAL);
     Require(scePthreadJoin(nullptr, nullptr) == SCE_KERNEL_ERROR_EINVAL);
     Require(scePthreadDetach(nullptr) == SCE_KERNEL_ERROR_EINVAL);