From 32b8c341eef3b84fd1965b3398eb2dac7c16b316 Mon Sep 17 00:00:00 2001
From: "Herman S." <429230+has207@users.noreply.github.com>
Date: Sun, 12 Oct 2025 20:30:29 +0900
Subject: [PATCH] [Kernel] ReleaseSemaphore for Posix to match Windows
 semantics

---
 src/xenia/base/threading_posix.cc               | 15 ++++++++-------
 src/xenia/kernel/xboxkrnl/xboxkrnl_threading.cc | 17 +++++++++++++++--
 src/xenia/kernel/xsemaphore.cc                  | 10 +++++++---
 src/xenia/kernel/xsemaphore.h                   |  3 ++-
 4 files changed, 32 insertions(+), 13 deletions(-)

diff --git a/src/xenia/base/threading_posix.cc b/src/xenia/base/threading_posix.cc
index c8549ecfb..a2c634d08 100644
--- a/src/xenia/base/threading_posix.cc
+++ b/src/xenia/base/threading_posix.cc
@@ -320,14 +320,15 @@ class PosixCondition<Semaphore> final : public PosixConditionBase {
   bool Signal() override { return Release(1, nullptr); }
 
   bool Release(uint32_t release_count, int* out_previous_count) {
-    if (maximum_count_ - count_ >= release_count) {
-      auto lock = std::unique_lock(mutex_);
-      if (out_previous_count) *out_previous_count = count_;
-      count_ += release_count;
-      cond_.notify_all();
-      return true;
+    auto lock = std::unique_lock(mutex_);
+    // Validate that releasing would not exceed the maximum count
+    if (count_ + release_count > maximum_count_) {
+      return false;
     }
-    return false;
+    if (out_previous_count) *out_previous_count = count_;
+    count_ += release_count;
+    cond_.notify_all();
+    return true;
   }
 
  private:
diff --git a/src/xenia/kernel/xboxkrnl/xboxkrnl_threading.cc b/src/xenia/kernel/xboxkrnl/xboxkrnl_threading.cc
index e6fa86ba1..fba756fee 100644
--- a/src/xenia/kernel/xboxkrnl/xboxkrnl_threading.cc
+++ b/src/xenia/kernel/xboxkrnl/xboxkrnl_threading.cc
@@ -718,7 +718,10 @@ uint32_t xeKeReleaseSemaphore(X_KSEMAPHORE* semaphore_ptr, uint32_t increment,
   // TODO(benvanik): increment thread priority?
   // TODO(benvanik): wait?
 
-  return sem->ReleaseSemaphore(adjustment);
+  int32_t previous_count = 0;
+  [[maybe_unused]] bool success =
+      sem->ReleaseSemaphore(adjustment, &previous_count);
+  return static_cast<uint32_t>(previous_count);
 }
 
 dword_result_t KeReleaseSemaphore_entry(pointer_t<X_KSEMAPHORE> semaphore_ptr,
@@ -777,7 +780,17 @@ dword_result_t NtReleaseSemaphore_entry(dword_t sem_handle,
   auto sem =
       kernel_state()->object_table()->LookupObject<XSemaphore>(sem_handle);
   if (sem) {
-    previous_count = sem->ReleaseSemaphore((int32_t)release_count);
+    bool success =
+        sem->ReleaseSemaphore((int32_t)release_count, &previous_count);
+    if (!success) {
+      // Releasing would exceed the semaphore's maximum count
+      // Windows returns STATUS_SEMAPHORE_LIMIT_EXCEEDED (0x0000012B)
+      XELOGW(
+          "NtReleaseSemaphore: release_count={} would exceed maximum (current "
+          "count={})",
+          uint32_t(release_count), previous_count);
+      result = 0x0000012B;
+    }
   } else {
     result = X_STATUS_INVALID_HANDLE;
   }
diff --git a/src/xenia/kernel/xsemaphore.cc b/src/xenia/kernel/xsemaphore.cc
index 34b960b25..f04d0826e 100644
--- a/src/xenia/kernel/xsemaphore.cc
+++ b/src/xenia/kernel/xsemaphore.cc
@@ -40,10 +40,14 @@ bool XSemaphore::InitializeNative(void* native_ptr, X_DISPATCH_HEADER* header) {
   return !!semaphore_;
 }
 
-int32_t XSemaphore::ReleaseSemaphore(int32_t release_count) {
+bool XSemaphore::ReleaseSemaphore(int32_t release_count,
+                                  int32_t* out_previous_count) {
   int32_t previous_count = 0;
-  semaphore_->Release(release_count, &previous_count);
-  return previous_count;
+  bool success = semaphore_->Release(release_count, &previous_count);
+  if (out_previous_count) {
+    *out_previous_count = previous_count;
+  }
+  return success;
 }
 
 bool XSemaphore::Save(ByteStream* stream) {
diff --git a/src/xenia/kernel/xsemaphore.h b/src/xenia/kernel/xsemaphore.h
index 77278af9f..2135fdec3 100644
--- a/src/xenia/kernel/xsemaphore.h
+++ b/src/xenia/kernel/xsemaphore.h
@@ -29,7 +29,8 @@ class XSemaphore : public XObject {
   [[nodiscard]] bool InitializeNative(void* native_ptr,
                                       X_DISPATCH_HEADER* header);
 
-  int32_t ReleaseSemaphore(int32_t release_count);
+  [[nodiscard]] bool ReleaseSemaphore(int32_t release_count,
+                                      int32_t* out_previous_count);
 
   bool Save(ByteStream* stream) override;
   static object_ref<XSemaphore> Restore(KernelState* kernel_state,