diff --git a/services/surfaceflinger/SurfaceFlinger.cpp b/services/surfaceflinger/SurfaceFlinger.cpp
index c37028e..42eef04 100644
--- a/services/surfaceflinger/SurfaceFlinger.cpp
+++ b/services/surfaceflinger/SurfaceFlinger.cpp
@@ -3478,7 +3478,7 @@
                 break;
             }
             applyTransactionState(states, displays, flags, mPendingInputWindowCommands,
-                                  desiredPresentTime, postTime, privileged);
+                                  desiredPresentTime, postTime, privileged, /*isMainThread*/ true);
             transactionQueue.pop();
         }
 
@@ -3565,7 +3565,7 @@
                                            const Vector<DisplayState>& displays, uint32_t flags,
                                            const InputWindowCommands& inputWindowCommands,
                                            const int64_t desiredPresentTime, const int64_t postTime,
-                                           bool privileged) {
+                                           bool privileged, bool isMainThread) {
     uint32_t transactionFlags = 0;
 
     if (flags & eAnimation) {
@@ -3629,7 +3629,12 @@
         }
 
         mPendingSyncInputWindows = mPendingInputWindowCommands.syncInputWindows;
-        while (mTransactionPending || mPendingSyncInputWindows) {
+
+        // applyTransactionState can be called by either the main SF thread or by
+        // another process through setTransactionState.  While a given process may wish
+        // to wait on synchronous transactions, the main SF thread should never
+        // be blocked.  Therefore, we only wait if isMainThread is false.
+        while (!isMainThread && (mTransactionPending || mPendingSyncInputWindows)) {
             status_t err = mTransactionCV.waitRelative(mStateLock, s2ns(5));
             if (CC_UNLIKELY(err != NO_ERROR)) {
                 // just in case something goes wrong in SF, return to the
diff --git a/services/surfaceflinger/SurfaceFlinger.h b/services/surfaceflinger/SurfaceFlinger.h
index 776d39b..d159a1f 100644
--- a/services/surfaceflinger/SurfaceFlinger.h
+++ b/services/surfaceflinger/SurfaceFlinger.h
@@ -576,7 +576,7 @@
                                const Vector<DisplayState>& displays, uint32_t flags,
                                const InputWindowCommands& inputWindowCommands,
                                const int64_t desiredPresentTime, const int64_t postTime,
-                               bool privileged) REQUIRES(mStateLock);
+                               bool privileged, bool isMainThread = false) REQUIRES(mStateLock);
     bool flushTransactionQueues();
     uint32_t getTransactionFlags(uint32_t flags);
     uint32_t peekTransactionFlags();