Do not recreate destroyed singletons during shutdown (#31)

deleteAll() used to let getInstance() build a replacement, which crashed
when the script-editor server posted a toast after LLUI was gone. Shutdown
now refuses that construction, and notification adds do nothing once the
notification system is gone.

2 files changed, 30 insertions, 0 deletions

diff --git a/indra/llcommon/llsingleton.cpp b/indra/llcommon/llsingleton.cpp
index 05dc3cde79..46659e6b7b 100644
--- a/indra/llcommon/llsingleton.cpp
+++ b/indra/llcommon/llsingleton.cpp
@@ -27,6 +27,8 @@
 #include "linden_common.h"
 #include "llsingleton.h"
 
+#include <atomic>
+
 #include "llerror.h"
 #include "llerrorcontrol.h"
 #include "lldependencies.h"
@@ -406,8 +408,19 @@ void LLSingletonBase::cleanup_()
 }
 
 //static
+namespace
+{
+    std::atomic<bool> sShuttingDown{false};
+}
+
+bool LLSingletonBase::shuttingDown()
+{
+    return sShuttingDown.load(std::memory_order_acquire);
+}
+
 void LLSingletonBase::deleteAll()
 {
+    sShuttingDown.store(true, std::memory_order_release);
     // It's essential to traverse these in dependency order.
     for (LLSingletonBase* sp : dep_sort())
     {
diff --git a/indra/llcommon/llsingleton.h b/indra/llcommon/llsingleton.h
index ebef2489ce..c088f7a9c4 100644
--- a/indra/llcommon/llsingleton.h
+++ b/indra/llcommon/llsingleton.h
@@ -46,6 +46,9 @@ class LLSingletonBase
 {
 public:
     class MasterList;
+    // True once deleteAll() has started. getInstance() must not construct
+    // a replacement for a singleton that shutdown has already destroyed.
+    static bool shuttingDown();
 
     LLSingletonBase(const LLSingletonBase&) = delete;
     LLSingletonBase& operator=(const LLSingletonBase&) = delete;
@@ -533,6 +536,13 @@ public:
 
             case DELETED:
                 // called after deleteSingleton()
+                if (LLSingletonBase::shuttingDown())
+                {
+                    logwarns({"Refusing to recreate deleted singleton ",
+                             classname<DERIVED_TYPE>(),
+                             " during shutdown"});
+                    return nullptr;
+                }
                 logwarns({"Trying to access deleted singleton ",
                          classname<DERIVED_TYPE>(),
                          " -- creating new instance"});
@@ -540,6 +550,13 @@ public:
                 [[fallthrough]];
             case UNINITIALIZED:
             case QUEUED:
+                if (LLSingletonBase::shuttingDown())
+                {
+                    logwarns({"Refusing to construct singleton ",
+                             classname<DERIVED_TYPE>(),
+                             " during shutdown"});
+                    return nullptr;
+                }
                 // QUEUED means some secondary thread has already requested an
                 // instance, but for present purposes that's semantically
                 // identical to UNINITIALIZED: either way, we must ourselves