Hold mPropLock when deferring updates

4 files changed, 15 insertions, 4 deletions

diff --git a/al/state.cpp b/al/state.cpp
index bd62c4e3..6da55d6f 100644
--- a/al/state.cpp
+++ b/al/state.cpp
@@ -878,6 +878,7 @@ START_API_FUNC
     ContextRef context{GetContextRef()};
     if UNLIKELY(!context) return;
 
+    std::lock_guard<std::mutex> _{context->mPropLock};
     context->deferUpdates();
 }
 END_API_FUNC
@@ -888,6 +889,7 @@ START_API_FUNC
     ContextRef context{GetContextRef()};
     if UNLIKELY(!context) return;
 
+    std::lock_guard<std::mutex> _{context->mPropLock};
     context->processUpdates();
 }
 END_API_FUNC
diff --git a/alc/alc.cpp b/alc/alc.cpp
index 82e31667..1659593f 100644
--- a/alc/alc.cpp
+++ b/alc/alc.cpp
@@ -2292,7 +2292,10 @@ START_API_FUNC
     if(!ctx)
         alcSetError(nullptr, ALC_INVALID_CONTEXT);
     else
+    {
+        std::lock_guard<std::mutex> _{ctx->mPropLock};
         ctx->deferUpdates();
+    }
 }
 END_API_FUNC
 
@@ -2306,7 +2309,10 @@ START_API_FUNC
     if(!ctx)
         alcSetError(nullptr, ALC_INVALID_CONTEXT);
     else
+    {
+        std::lock_guard<std::mutex> _{ctx->mPropLock};
         ctx->processUpdates();
+    }
 }
 END_API_FUNC
 
diff --git a/alc/context.cpp b/alc/context.cpp
index 290c4f01..ea806d95 100644
--- a/alc/context.cpp
+++ b/alc/context.cpp
@@ -249,7 +249,6 @@ bool ALCcontext::deinit()
 
 void ALCcontext::processUpdates()
 {
-    std::lock_guard<std::mutex> _{mPropLock};
     if(mDeferUpdates.exchange(false, std::memory_order_acq_rel))
     {
         /* Tell the mixer to stop applying updates, then wait for any active
diff --git a/alc/context.h b/alc/context.h
index b22aaf62..22c2418a 100644
--- a/alc/context.h
+++ b/alc/context.h
@@ -153,11 +153,15 @@ struct ALCcontext : public al::intrusive_ref<ALCcontext>, ContextBase {
     /**
      * Defers/suspends updates for the given context's listener and sources.
      * This does *NOT* stop mixing, but rather prevents certain property
-     * changes from taking effect.
+     * changes from taking effect. mPropLock must be held when called.
      */
-    void deferUpdates() noexcept { mDeferUpdates.exchange(true, std::memory_order_acq_rel); }
+    bool deferUpdates() noexcept
+    { return mDeferUpdates.exchange(true, std::memory_order_acq_rel); }
 
-    /** Resumes update processing after being deferred. */
+    /**
+     * Resumes update processing after being deferred. mPropLock must be held
+     * when called.
+     */
     void processUpdates();
 
 #ifdef __USE_MINGW_ANSI_STDIO