kernel: fix unbounded stack usage in atomics

src/core/hle/kernel/k_address_arbiter.cpp

@@ -35,8 +35,11 @@ bool DecrementIfLessThan(Core::System& system, s32* out, KProcessAddress address
 
     // TODO(bunnei): We should call CanAccessAtomic(..) here.
 
+    s32 current_value{};
+
+    while (true) {
         // Load the value from the address.
-    const s32 current_value =
+        current_value =
             static_cast<s32>(monitor.ExclusiveRead32(current_core, GetInteger(address)));
 
         // Compare it to the desired one.
@@ -45,14 +48,17 @@ bool DecrementIfLessThan(Core::System& system, s32* out, KProcessAddress address
             const s32 decrement_value = current_value - 1;
 
             // Decrement and try to store.
-        if (!monitor.ExclusiveWrite32(current_core, GetInteger(address),
+            if (monitor.ExclusiveWrite32(current_core, GetInteger(address),
                                          static_cast<u32>(decrement_value))) {
-            // If we failed to store, try again.
-            DecrementIfLessThan(system, out, address, value);
+                break;
             }
+
+            // If we failed to store, try again.
         } else {
             // Otherwise, clear our exclusive hold and finish
             monitor.ClearExclusive(current_core);
+            break;
+        }
     }
 
     // We're done.
@@ -70,8 +76,11 @@ bool UpdateIfEqual(Core::System& system, s32* out, KProcessAddress address, s32
 
     // TODO(bunnei): We should call CanAccessAtomic(..) here.
 
+    s32 current_value{};
+
     // Load the value from the address.
-    const s32 current_value =
+    while (true) {
+        current_value =
             static_cast<s32>(monitor.ExclusiveRead32(current_core, GetInteger(address)));
 
         // Compare it to the desired one.
@@ -79,14 +88,17 @@ bool UpdateIfEqual(Core::System& system, s32* out, KProcessAddress address, s32
             // If equal, we want to try to write the new value.
 
             // Try to store.
-        if (!monitor.ExclusiveWrite32(current_core, GetInteger(address),
+            if (monitor.ExclusiveWrite32(current_core, GetInteger(address),
                                          static_cast<u32>(new_value))) {
-            // If we failed to store, try again.
-            UpdateIfEqual(system, out, address, value, new_value);
+                break;
             }
+
+            // If we failed to store, try again.
         } else {
             // Otherwise, clear our exclusive hold and finish.
             monitor.ClearExclusive(current_core);
+            break;
+        }
     }
 
     // We're done.

src/core/hle/kernel/k_condition_variable.cpp

@@ -33,8 +33,11 @@ bool UpdateLockAtomic(Core::System& system, u32* out, KProcessAddress address, u
     auto& monitor = system.Monitor();
     const auto current_core = system.Kernel().CurrentPhysicalCoreIndex();
 
+    u32 expected{};
+
+    while (true) {
         // Load the value from the address.
-    const auto expected = monitor.ExclusiveRead32(current_core, GetInteger(address));
+        expected = monitor.ExclusiveRead32(current_core, GetInteger(address));
 
         // Orr in the new mask.
         u32 value = expected | new_orr_mask;
@@ -45,9 +48,11 @@ bool UpdateLockAtomic(Core::System& system, u32* out, KProcessAddress address, u
         }
 
         // Try to store.
-    if (!monitor.ExclusiveWrite32(current_core, GetInteger(address), value)) {
+        if (monitor.ExclusiveWrite32(current_core, GetInteger(address), value)) {
+            break;
+        }
+
         // If we failed to store, try again.
-        return UpdateLockAtomic(system, out, address, if_zero, new_orr_mask);
     }
 
     // We're done.