From d383ef210b0732b86224a1a5a3f49f4c84a1fecb Mon Sep 17 00:00:00 2001
From: Matthew Stanley <1379tech@gmail.com>
Date: Thu, 22 Oct 2026 17:03:06 -0700
Subject: [PATCH] Drain and reset session HUD callbacks

---
 runtime/CMakeLists.txt             |  1 +
 runtime/include/host_overlay.h     |  6 +++--
 runtime/src/gpu_gl_renderer.c      |  1 +
 runtime/src/host_overlay.c         | 34 +++++++++++++++++++++++++-
 runtime/src/mod_runtime.cpp        |  3 +++
 runtime/tests/test_host_overlay.c  | 38 ++++++++++++++++++++++++++++++
 runtime/tests/test_mod_runtime.cpp |  6 +++++
 7 files changed, 86 insertions(+), 3 deletions(-)

diff --git a/runtime/CMakeLists.txt b/runtime/CMakeLists.txt
index 0340c49d..85843c06 100644
--- a/runtime/CMakeLists.txt
+++ b/runtime/CMakeLists.txt
@@ -1396,6 +1396,7 @@ if(BUILD_TESTING)
 
     add_executable(mod_runtime_test
         src/mod_immediate.c
+        src/host_overlay.c
         tests/test_mod_runtime.cpp
         src/iso_reader_c.cpp
         src/host_span_ring.c
diff --git a/runtime/include/host_overlay.h b/runtime/include/host_overlay.h
index d1bfcf3f..0a2cd648 100644
--- a/runtime/include/host_overlay.h
+++ b/runtime/include/host_overlay.h
@@ -49,8 +49,10 @@ void psx_host_overlay_draw(int width, int height);  /* renderer side */
 /* ---- Game HUD layer ---------------------------------------------------------
  * A title's own heads-up display, drawn once per presented frame (real and
  * generated) under the in-game menu, same thread and GL rules as the overlay
- * callback above. Set once (title activation) and kept for the session; NULL
- * unregisters (no wait: the registrant keeps fn and ctx alive for the session). */
+ * callback above. OpenGL only; Vulkan and the SDL renderer never invoke it.
+ * Replacing or NULL unregistering drains prior calls as for the overlay above;
+ * the owner may then release its old context. Registration is session-scoped:
+ * activation reset and GL shutdown clear it. Register again on activation. */
 void psx_host_set_hud_draw_cb(PsxHostOverlayDrawFn fn, void *ctx);
 void psx_host_hud_draw(int width, int height);  /* renderer side */
 
diff --git a/runtime/src/gpu_gl_renderer.c b/runtime/src/gpu_gl_renderer.c
index 67b2f4a0..87d2c5bc 100644
--- a/runtime/src/gpu_gl_renderer.c
+++ b/runtime/src/gpu_gl_renderer.c
@@ -6550,6 +6550,7 @@ static void pass_resources_release(void);
 static void present_image_ring_gl_forget(void);
 void gl_renderer_shutdown(void) {
     gl_renderer_render_thread_stop();   /* drains; the context comes back to this thread */
+    psx_host_set_hud_draw_cb(NULL, NULL);
     /* After the worker has stopped (it presents, and captures, on its own
      * thread) and before the context dies: forget the ring's GL names. */
     present_image_ring_gl_forget();
diff --git a/runtime/src/host_overlay.c b/runtime/src/host_overlay.c
index dfc7536c..83463a74 100644
--- a/runtime/src/host_overlay.c
+++ b/runtime/src/host_overlay.c
@@ -104,15 +104,47 @@ void psx_host_overlay_draw(int width, int height) {
 /* ---- Game HUD layer ------------------------------------------------------- */
 static PsxHostOverlayDrawFn s_hud_fn = NULL;
 static void *s_hud_ctx = NULL;
+static atomic_flag s_hud_lock = ATOMIC_FLAG_INIT;
+static atomic_int s_hud_inflight = 0;
+#if defined(_MSC_VER)
+static __declspec(thread) int s_in_hud = 0;
+#else
+static _Thread_local int s_in_hud = 0;
+#endif
+
+static void hud_lock(void) {
+    while (atomic_flag_test_and_set_explicit(&s_hud_lock, memory_order_acquire))
+        draw_yield();
+}
+static void hud_unlock(void) {
+    atomic_flag_clear_explicit(&s_hud_lock, memory_order_release);
+}
 
 void psx_host_set_hud_draw_cb(PsxHostOverlayDrawFn fn, void *ctx) {
+    hud_lock();
     s_hud_ctx = ctx;
     s_hud_fn = fn;
+    hud_unlock();
+    /* Match the overlay lifetime contract without allocating callback records.
+     * The single GL owner may unregister itself; its current call then ends
+     * before another frame can consume the replacement. */
+    if (!s_in_hud)
+        while (atomic_load(&s_hud_inflight) > 0) draw_yield();
 }
 
 void psx_host_hud_draw(int width, int height) {
+    if (width <= 0 || height <= 0) return;
+    hud_lock();
     PsxHostOverlayDrawFn fn = s_hud_fn;
-    if (fn && width > 0 && height > 0) fn(width, height, s_hud_ctx);
+    void *ctx = s_hud_ctx;
+    atomic_fetch_add(&s_hud_inflight, 1);
+    hud_unlock();
+    if (fn) {
+        s_in_hud = 1;
+        fn(width, height, ctx);
+        s_in_hud = 0;
+    }
+    atomic_fetch_sub(&s_hud_inflight, 1);
 }
 
 /* ---- P3: input sink -------------------------------------------------------- */
diff --git a/runtime/src/mod_runtime.cpp b/runtime/src/mod_runtime.cpp
index 5bfe6257..28792e85 100644
--- a/runtime/src/mod_runtime.cpp
+++ b/runtime/src/mod_runtime.cpp
@@ -1,5 +1,6 @@
 #include "mod_runtime.h"
 #include "host_launch_timing.h"
+#include "host_overlay.h"
 #include "cpu_state.h"
 
 #include "disc_path.h"
@@ -2963,6 +2964,8 @@ bool mod_runtime_read_disc_file_sectors(const std::string& path, uint32_t max_by
 extern "C" void mod_runtime_activate_plugins(void) {
     using namespace PSXRecompV4;
     HostLaunchTimingScope timing(HOST_LAUNCH_PLUGIN_ACTIVATION);
+    /* Drain session-owned presentation callbacks before their contexts reset. */
+    psx_host_set_hud_draw_cb(nullptr, nullptr);
     mod_reset_plugin_sessions();
     RuntimeMods& s = state();
     s.ticket_ready = false;
diff --git a/runtime/tests/test_host_overlay.c b/runtime/tests/test_host_overlay.c
index 1aaecd67..4045d61e 100644
--- a/runtime/tests/test_host_overlay.c
+++ b/runtime/tests/test_host_overlay.c
@@ -75,6 +75,29 @@ static void* life_reader(void* arg) {
     while (!atomic_load(&g_stop)) psx_host_overlay_draw(64, 64);
     return NULL;
 }
+static void* hud_life_reader(void* arg) {
+    (void)arg;
+    while (!atomic_load(&g_stop)) psx_host_hud_draw(64, 64);
+    return NULL;
+}
+static void test_hud_lifetime(void) {
+    pthread_t t;
+    atomic_store(&g_stop, 0);
+    pthread_create(&t, NULL, hud_life_reader, NULL);
+    for (int round = 0; round < 100; ++round) {
+        LifeCtx* c = (LifeCtx*)calloc(1, sizeof(*c));
+        atomic_store(&c->alive, 1);
+        psx_host_set_hud_draw_cb(life_draw, c);
+        while (atomic_load(&c->calls) < 2) {}
+        /* Also models the activation-reset / renderer-shutdown clear. */
+        psx_host_set_hud_draw_cb(NULL, NULL);
+        atomic_store(&c->alive, 0);
+        CHECK(atomic_load(&c->used_dead) == 0);
+        free(c);
+    }
+    atomic_store(&g_stop, 1);
+    pthread_join(t, NULL);
+}
 static void test_draw_lifetime(void) {
     pthread_t t;
     atomic_store(&g_stop, 0);
@@ -99,6 +122,7 @@ static void test_draw_lifetime(void) {
 }
 #else
 static void test_draw_lifetime(void) {}
+static void test_hud_lifetime(void) {}
 #endif
 
 /* Changing the callback from inside it must not deadlock. */
@@ -114,6 +138,18 @@ static void test_draw_reentrant(void) {
     psx_host_overlay_draw(64, 64);
     CHECK(n == 1 && !psx_host_overlay_has_draw());
 }
+static void hud_self_unregister(int w, int h, void* p) {
+    (void)w; (void)h;
+    ++*(int*)p;
+    psx_host_set_hud_draw_cb(NULL, NULL);
+}
+static void test_hud_reentrant(void) {
+    int calls = 0;
+    psx_host_set_hud_draw_cb(hud_self_unregister, &calls);
+    psx_host_hud_draw(64, 64);
+    psx_host_hud_draw(64, 64);
+    CHECK(calls == 1);
+}
 
 static int sunk = 0;
 static int sink(const void *ev, void *ctx) { (void)ctx; sunk++; return *(const int *)ev == 1; }
@@ -237,6 +273,8 @@ static void test_cmdline_quote(void) {
 }
 
 int main(void) {
+    test_hud_lifetime();
+    test_hud_reentrant();
     test_draw_lifetime();
     test_draw_reentrant();
     test_cmdline_quote();
diff --git a/runtime/tests/test_mod_runtime.cpp b/runtime/tests/test_mod_runtime.cpp
index 71680a21..ba605da2 100644
--- a/runtime/tests/test_mod_runtime.cpp
+++ b/runtime/tests/test_mod_runtime.cpp
@@ -1,6 +1,7 @@
 #include "mod_runtime.h"
 #include "mod_netplay.h"
 #include "host_launch_timing.h"
+#include "host_overlay.h"
 #include "host_file_identity.h"
 #include "mod_packages.h"
 #include "mod_plugins.h"
@@ -107,6 +108,8 @@ extern "C" uint32_t psx_mod_gpu_dma_memory_alloc(uint32_t, uint32_t) {
 }
 extern "C" void psx_ram_reset_size_request(void) {}
 static int hd_shutdown_calls, hd_configure_calls, hd_dump_value;
+static int hud_calls;
+static void old_session_hud(int, int, void*) { ++hud_calls; }
 static int hd_replacements_value, hd_reload_calls;
 static std::string hd_root;
 extern "C" void gpu_hd_textures_shutdown(void) { ++hd_shutdown_calls; hd_root.clear(); }
@@ -724,7 +727,10 @@ int main(int argc, char** argv) {
     psx_mod_function_entry(&entry_cpu, 0x80003000u);
     check(g_psx_mod_function_entry_hooks == 0 && active_entry_hits == 0,
           "function-entry hooks must not run before plugin activation");
+    psx_host_set_hud_draw_cb(old_session_hud, nullptr);
     mod_runtime_activate_plugins();
+    psx_host_hud_draw(64, 64);
+    check(hud_calls == 0, "activation clears the prior session HUD before resetting plugins");
     check(activation_calls == 1,
           "resolved trusted plugin must activate before runtime startup");
     entry_cpu.pc = 0x80004000u;