From 008eb974d43658d96c0b8d667975d3897303b42a Mon Sep 17 00:00:00 2001
From: Michael Scire <SciresM@gmail.com>
Date: Tue, 21 Feb 2023 10:42:24 -0700
Subject: [PATCH] kern: KConditionVariable::SignalToAddress now emits dmb
 before userspace write

---
 .../source/kern_k_condition_variable.cpp      | 37 ++++++++++---------
 1 file changed, 19 insertions(+), 18 deletions(-)

diff --git a/libraries/libmesosphere/source/kern_k_condition_variable.cpp b/libraries/libmesosphere/source/kern_k_condition_variable.cpp
index 6dc2b25b6..138602cfb 100644
--- a/libraries/libmesosphere/source/kern_k_condition_variable.cpp
+++ b/libraries/libmesosphere/source/kern_k_condition_variable.cpp
@@ -78,7 +78,7 @@ namespace ams::kern {
 
             /* Remove waiter thread. */
             s32 num_waiters;
-            KThread *next_owner_thread = owner_thread->RemoveWaiterByKey(std::addressof(num_waiters), addr);
+            KThread * const next_owner_thread = owner_thread->RemoveWaiterByKey(std::addressof(num_waiters), addr);
 
             /* Determine the next tag. */
             u32 next_value = 0;
@@ -87,24 +87,25 @@ namespace ams::kern {
                 if (num_waiters > 1) {
                     next_value |= ams::svc::HandleWaitMask;
                 }
-
-                /* Write the value to userspace. */
-                Result result;
-                if (AMS_LIKELY(WriteToUser(addr, std::addressof(next_value)))) {
-                    result = ResultSuccess();
-                } else {
-                    result = svc::ResultInvalidCurrentMemory();
-                }
-
-                /* Signal the next owner thread. */
-                next_owner_thread->EndWait(result);
-                R_RETURN(result);
-            } else {
-                /* Just write the value to userspace. */
-                R_UNLESS(WriteToUser(addr, std::addressof(next_value)), svc::ResultInvalidCurrentMemory());
-
-                R_SUCCEED();
             }
+
+            /* Synchronize memory before proceeding. */
+            cpu::DataMemoryBarrierInnerShareable();
+
+            /* Write the value to userspace. */
+            Result result;
+            if (AMS_LIKELY(WriteToUser(addr, std::addressof(next_value)))) {
+                result = ResultSuccess();
+            } else {
+                result = svc::ResultInvalidCurrentMemory();
+            }
+
+            /* If necessary, signal the next owner thread. */
+            if (next_owner_thread != nullptr) {
+                next_owner_thread->EndWait(result);
+            }
+
+            R_RETURN(result);
         }
     }