diff --git a/camera/camera_platform.aconfig b/camera/camera_platform.aconfig
index 63a514d..2266483 100644
--- a/camera/camera_platform.aconfig
+++ b/camera/camera_platform.aconfig
@@ -90,3 +90,10 @@
      description: "Only trigger lazy HAL instantiation when the HAL is needed for an operation."
      bug: "319735068"
 }
+
+flag {
+     namespace: "camera_platform"
+     name: "return_buffers_outside_locks"
+     description: "Enable returning graphics buffers to buffer queues without holding the in-flight mutex"
+     bug: "315526878"
+}
diff --git a/services/camera/libcameraservice/device3/Camera3OutputUtils.cpp b/services/camera/libcameraservice/device3/Camera3OutputUtils.cpp
index 5d5c54c..f764645 100644
--- a/services/camera/libcameraservice/device3/Camera3OutputUtils.cpp
+++ b/services/camera/libcameraservice/device3/Camera3OutputUtils.cpp
@@ -499,7 +499,8 @@
     states.inflightIntf.onInflightEntryRemovedLocked(duration);
 }
 
-void removeInFlightRequestIfReadyLocked(CaptureOutputStates& states, int idx) {
+void removeInFlightRequestIfReadyLocked(CaptureOutputStates& states, int idx,
+        std::vector<BufferToReturn> *returnableBuffers) {
     InFlightRequestMap& inflightMap = states.inflightMap;
     const InFlightRequest &request = inflightMap.valueAt(idx);
     const uint32_t frameNumber = inflightMap.keyAt(idx);
@@ -537,12 +538,13 @@
         assert(request.requestStatus != OK ||
                request.pendingOutputBuffers.size() == 0);
 
-        returnOutputBuffers(
+        collectReturnableOutputBuffers(
             states.useHalBufManager, states.halBufManagedStreamIds,
             states.listener,
             request.pendingOutputBuffers.array(),
             request.pendingOutputBuffers.size(), /*timestamp*/0, /*readoutTimestamp*/0,
             /*requested*/true, request.requestTimeNs, states.sessionStatsBuilder,
+            /*out*/ returnableBuffers,
             /*timestampIncreasing*/true,
             request.outputSurfaces, request.resultExtras,
             request.errorBufStrategy, request.transform);
@@ -637,6 +639,7 @@
     // in-flight request and they will be returned when the shutter timestamp
     // arrives. Update the in-flight status and remove the in-flight entry if
     // all result data and shutter timestamp have been received.
+    std::vector<BufferToReturn> returnableBuffers{};
     nsecs_t shutterTimestamp = 0;
     {
         std::lock_guard<std::mutex> l(states.inflightLock);
@@ -798,10 +801,11 @@
         request.pendingOutputBuffers.appendArray(result->output_buffers,
                 result->num_output_buffers);
         if (shutterTimestamp != 0) {
-            returnAndRemovePendingOutputBuffers(
+            collectAndRemovePendingOutputBuffers(
                 states.useHalBufManager, states.halBufManagedStreamIds,
                 states.listener,
-                request, states.sessionStatsBuilder);
+                request, states.sessionStatsBuilder,
+                /*out*/ &returnableBuffers);
         }
 
         if (result->result != NULL && !isPartialResult) {
@@ -826,9 +830,18 @@
                     request.physicalMetadatas);
             }
         }
-        removeInFlightRequestIfReadyLocked(states, idx);
+        removeInFlightRequestIfReadyLocked(states, idx, &returnableBuffers);
+        if (!flags::return_buffers_outside_locks()) {
+            finishReturningOutputBuffers(returnableBuffers,
+                states.listener, states.sessionStatsBuilder);
+        }
     } // scope for states.inFlightLock
 
+    if (flags::return_buffers_outside_locks()) {
+        finishReturningOutputBuffers(returnableBuffers,
+                states.listener, states.sessionStatsBuilder);
+    }
+
     if (result->input_buffer != NULL) {
         if (hasInputBufferInRequest) {
             Camera3Stream *stream =
@@ -849,17 +862,17 @@
     }
 }
 
-void returnOutputBuffers(
+void collectReturnableOutputBuffers(
         bool useHalBufManager,
         const std::set<int32_t> &halBufferManagedStreams,
         sp<NotificationListener> listener,
         const camera_stream_buffer_t *outputBuffers, size_t numBuffers,
         nsecs_t timestamp, nsecs_t readoutTimestamp, bool requested,
         nsecs_t requestTimeNs, SessionStatsBuilder& sessionStatsBuilder,
+        /*out*/ std::vector<BufferToReturn> *returnableBuffers,
         bool timestampIncreasing, const SurfaceMap& outputSurfaces,
-        const CaptureResultExtras &inResultExtras,
+        const CaptureResultExtras &resultExtras,
         ERROR_BUF_STRATEGY errorBufStrategy, int32_t transform) {
-
     for (size_t i = 0; i < numBuffers; i++)
     {
         Camera3StreamInterface *stream = Camera3Stream::cast(outputBuffers[i].stream);
@@ -869,7 +882,7 @@
         if (outputBuffers[i].status == CAMERA_BUFFER_STATUS_ERROR &&
                 errorBufStrategy == ERROR_BUF_RETURN_NOTIFY) {
             if (listener != nullptr) {
-                CaptureResultExtras extras = inResultExtras;
+                CaptureResultExtras extras = resultExtras;
                 extras.errorStreamId = streamId;
                 listener->notifyError(
                         hardware::camera2::ICameraDeviceCallbacks::ERROR_CAMERA_BUFFER,
@@ -894,22 +907,35 @@
         }
 
         const auto& it = outputSurfaces.find(streamId);
-        status_t res = OK;
 
         // Do not return the buffer if the buffer status is error, and the error
         // buffer strategy is CACHE.
         if (outputBuffers[i].status != CAMERA_BUFFER_STATUS_ERROR ||
                 errorBufStrategy != ERROR_BUF_CACHE) {
             if (it != outputSurfaces.end()) {
-                res = stream->returnBuffer(
+                returnableBuffers->emplace_back(stream,
                         outputBuffers[i], timestamp, readoutTimestamp, timestampIncreasing,
-                        it->second, inResultExtras.frameNumber, transform);
+                        it->second, resultExtras,
+                        transform, requested ? requestTimeNs : 0);
             } else {
-                res = stream->returnBuffer(
+                returnableBuffers->emplace_back(stream,
                         outputBuffers[i], timestamp, readoutTimestamp, timestampIncreasing,
-                        std::vector<size_t> (), inResultExtras.frameNumber, transform);
+                        std::vector<size_t> (), resultExtras,
+                        transform, requested ? requestTimeNs : 0 );
             }
         }
+    }
+}
+
+void finishReturningOutputBuffers(const std::vector<BufferToReturn> &returnableBuffers,
+        sp<NotificationListener> listener, SessionStatsBuilder& sessionStatsBuilder) {
+    for (auto& b : returnableBuffers) {
+        const int streamId = b.stream->getId();
+
+        status_t res = b.stream->returnBuffer(b.buffer, b.timestamp,
+                b.readoutTimestamp, b.timestampIncreasing,
+                b.surfaceIds, b.resultExtras.frameNumber, b.transform);
+
         // Note: stream may be deallocated at this point, if this buffer was
         // the last reference to it.
         bool dropped = false;
@@ -920,51 +946,55 @@
             ALOGE("Can't return buffer to its stream: %s (%d)", strerror(-res), res);
             dropped = true;
         } else {
-            if (outputBuffers[i].status == CAMERA_BUFFER_STATUS_ERROR || timestamp == 0) {
+            if (b.buffer.status == CAMERA_BUFFER_STATUS_ERROR || b.timestamp == 0) {
                 dropped = true;
             }
         }
-        if (requested) {
+        if (b.requestTimeNs > 0) {
             nsecs_t bufferTimeNs = systemTime();
-            int32_t captureLatencyMs = ns2ms(bufferTimeNs - requestTimeNs);
+            int32_t captureLatencyMs = ns2ms(bufferTimeNs - b.requestTimeNs);
             sessionStatsBuilder.incCounter(streamId, dropped, captureLatencyMs);
         }
 
         // Long processing consumers can cause returnBuffer timeout for shared stream
         // If that happens, cancel the buffer and send a buffer error to client
-        if (it != outputSurfaces.end() && res == TIMED_OUT &&
-                outputBuffers[i].status == CAMERA_BUFFER_STATUS_OK) {
+        if (b.surfaceIds.size() > 0 && res == TIMED_OUT &&
+                b.buffer.status == CAMERA_BUFFER_STATUS_OK) {
             // cancel the buffer
-            camera_stream_buffer_t sb = outputBuffers[i];
+            camera_stream_buffer_t sb = b.buffer;
             sb.status = CAMERA_BUFFER_STATUS_ERROR;
-            stream->returnBuffer(sb, /*timestamp*/0, /*readoutTimestamp*/0,
-                    timestampIncreasing, std::vector<size_t> (),
-                    inResultExtras.frameNumber, transform);
+            b.stream->returnBuffer(sb, /*timestamp*/0, /*readoutTimestamp*/0,
+                    b.timestampIncreasing, std::vector<size_t> (),
+                    b.resultExtras.frameNumber, b.transform);
 
             if (listener != nullptr) {
-                CaptureResultExtras extras = inResultExtras;
+                CaptureResultExtras extras = b.resultExtras;
                 extras.errorStreamId = streamId;
                 listener->notifyError(
                         hardware::camera2::ICameraDeviceCallbacks::ERROR_CAMERA_BUFFER,
                         extras);
             }
         }
+
     }
 }
 
-void returnAndRemovePendingOutputBuffers(bool useHalBufManager,
+void collectAndRemovePendingOutputBuffers(bool useHalBufManager,
         const std::set<int32_t> &halBufferManagedStreams,
         sp<NotificationListener> listener, InFlightRequest& request,
-        SessionStatsBuilder& sessionStatsBuilder) {
+        SessionStatsBuilder& sessionStatsBuilder,
+        std::vector<BufferToReturn> *returnableBuffers) {
     bool timestampIncreasing =
             !((request.zslCapture && request.stillCapture) || request.hasInputBuffer);
     nsecs_t readoutTimestamp = request.resultExtras.hasReadoutTimestamp ?
             request.resultExtras.readoutTimestamp : 0;
-    returnOutputBuffers(useHalBufManager, halBufferManagedStreams, listener,
+    collectReturnableOutputBuffers(useHalBufManager, halBufferManagedStreams, listener,
             request.pendingOutputBuffers.array(),
             request.pendingOutputBuffers.size(),
             request.shutterTimestamp, readoutTimestamp,
-            /*requested*/true, request.requestTimeNs, sessionStatsBuilder, timestampIncreasing,
+            /*requested*/true, request.requestTimeNs, sessionStatsBuilder,
+            /*out*/ returnableBuffers,
+            timestampIncreasing,
             request.outputSurfaces, request.resultExtras,
             request.errorBufStrategy, request.transform);
 
@@ -984,6 +1014,8 @@
     ATRACE_CALL();
     ssize_t idx;
 
+    std::vector<BufferToReturn> returnableBuffers{};
+
     // Set timestamp for the request in the in-flight tracking
     // and get the request ID to send upstream
     {
@@ -1061,17 +1093,30 @@
                     r.hasInputBuffer, r.zslCapture && r.stillCapture,
                     r.rotateAndCropAuto, cameraIdsWithZoom, r.physicalMetadatas);
             }
-            returnAndRemovePendingOutputBuffers(
+            collectAndRemovePendingOutputBuffers(
                     states.useHalBufManager, states.halBufManagedStreamIds,
-                    states.listener, r, states.sessionStatsBuilder);
+                    states.listener, r, states.sessionStatsBuilder, &returnableBuffers);
 
-            removeInFlightRequestIfReadyLocked(states, idx);
+            if (!flags::return_buffers_outside_locks()) {
+                finishReturningOutputBuffers(returnableBuffers,
+                        states.listener, states.sessionStatsBuilder);
+            }
+
+            removeInFlightRequestIfReadyLocked(states, idx, &returnableBuffers);
+
         }
     }
     if (idx < 0) {
         SET_ERR("Shutter notification for non-existent frame number %d",
                 msg.frame_number);
     }
+    // With no locks held, finish returning buffers to streams, which may take a while since
+    // binder calls are involved
+    if (flags::return_buffers_outside_locks()) {
+        finishReturningOutputBuffers(returnableBuffers,
+                states.listener, states.sessionStatsBuilder);
+    }
+
 }
 
 void notifyError(CaptureOutputStates& states, const camera_error_msg_t &msg) {
@@ -1117,6 +1162,8 @@
             break;
         case hardware::camera2::ICameraDeviceCallbacks::ERROR_CAMERA_REQUEST:
         case hardware::camera2::ICameraDeviceCallbacks::ERROR_CAMERA_RESULT:
+        {
+            std::vector<BufferToReturn> returnableBuffers{};
             {
                 std::lock_guard<std::mutex> l(states.inflightLock);
                 ssize_t idx = states.inflightMap.indexOfKey(msg.frame_number);
@@ -1153,7 +1200,12 @@
 
                         // Check whether the buffers returned. If they returned,
                         // remove inflight request.
-                        removeInFlightRequestIfReadyLocked(states, idx);
+                        removeInFlightRequestIfReadyLocked(states, idx, &returnableBuffers);
+                        if (!flags::return_buffers_outside_locks()) {
+                            finishReturningOutputBuffers(returnableBuffers,
+                                    states.listener, states.sessionStatsBuilder);
+                        }
+
                     }
                 } else {
                     resultExtras.frameNumber = msg.frame_number;
@@ -1162,6 +1214,12 @@
                             resultExtras.frameNumber);
                 }
             }
+
+            if (flags::return_buffers_outside_locks()) {
+                finishReturningOutputBuffers(returnableBuffers,
+                        states.listener, states.sessionStatsBuilder);
+            }
+
             resultExtras.errorStreamId = streamId;
             if (states.listener != nullptr) {
                 states.listener->notifyError(errorCode, resultExtras);
@@ -1170,6 +1228,7 @@
                         states.cameraId.c_str(), __FUNCTION__);
             }
             break;
+        }
         case hardware::camera2::ICameraDeviceCallbacks::ERROR_CAMERA_BUFFER:
             // Do not depend on HAL ERROR_CAMERA_BUFFER to send buffer error
             // callback to the app. Rather, use STATUS_ERROR of image buffers.
@@ -1199,18 +1258,24 @@
 
 void flushInflightRequests(FlushInflightReqStates& states) {
     ATRACE_CALL();
+    std::vector<BufferToReturn> returnableBuffers{};
     { // First return buffers cached in inFlightMap
         std::lock_guard<std::mutex> l(states.inflightLock);
         for (size_t idx = 0; idx < states.inflightMap.size(); idx++) {
             const InFlightRequest &request = states.inflightMap.valueAt(idx);
-            returnOutputBuffers(
+            collectReturnableOutputBuffers(
                 states.useHalBufManager, states.halBufManagedStreamIds,
                 states.listener,
                 request.pendingOutputBuffers.array(),
                 request.pendingOutputBuffers.size(), /*timestamp*/0, /*readoutTimestamp*/0,
                 /*requested*/true, request.requestTimeNs, states.sessionStatsBuilder,
+                /*out*/ &returnableBuffers,
                 /*timestampIncreasing*/true, request.outputSurfaces, request.resultExtras,
                 request.errorBufStrategy);
+            if (!flags::return_buffers_outside_locks()) {
+                finishReturningOutputBuffers(returnableBuffers,
+                        states.listener, states.sessionStatsBuilder);
+            }
             ALOGW("%s: Frame %d |  Timestamp: %" PRId64 ", metadata"
                     " arrived: %s, buffers left: %d.\n", __FUNCTION__,
                     states.inflightMap.keyAt(idx), request.shutterTimestamp,
@@ -1221,6 +1286,10 @@
         states.inflightMap.clear();
         states.inflightIntf.onInflightMapFlushedLocked();
     }
+    if (flags::return_buffers_outside_locks()) {
+        finishReturningOutputBuffers(returnableBuffers,
+                states.listener, states.sessionStatsBuilder);
+    }
 
     // Then return all inflight buffers not returned by HAL
     std::vector<std::pair<int32_t, int32_t>> inflightKeys;
diff --git a/services/camera/libcameraservice/device3/Camera3OutputUtils.h b/services/camera/libcameraservice/device3/Camera3OutputUtils.h
index d155fa2..75864d7 100644
--- a/services/camera/libcameraservice/device3/Camera3OutputUtils.h
+++ b/services/camera/libcameraservice/device3/Camera3OutputUtils.h
@@ -44,16 +44,50 @@
      * Helper methods shared between Camera3Device/Camera3OfflineSession for HAL callbacks
      */
 
-    // helper function to return the output buffers to output streams. The
-    // function also optionally calls notify(ERROR_BUFFER).
-    void returnOutputBuffers(
+    struct BufferToReturn {
+        Camera3StreamInterface *stream;
+        camera_stream_buffer_t buffer;
+        nsecs_t timestamp;
+        nsecs_t readoutTimestamp;
+        bool timestampIncreasing;
+        std::vector<size_t> surfaceIds;
+        const CaptureResultExtras resultExtras;
+        int32_t transform;
+        nsecs_t requestTimeNs;
+
+        BufferToReturn(Camera3StreamInterface *stream,
+                camera_stream_buffer_t buffer,
+                nsecs_t timestamp, nsecs_t readoutTimestamp,
+                bool timestampIncreasing, std::vector<size_t> surfaceIds,
+                const CaptureResultExtras &resultExtras,
+                int32_t transform, nsecs_t requestTimeNs):
+            stream(stream),
+            buffer(buffer),
+            timestamp(timestamp),
+            readoutTimestamp(readoutTimestamp),
+            timestampIncreasing(timestampIncreasing),
+            surfaceIds(surfaceIds),
+            resultExtras(resultExtras),
+            transform(transform),
+            requestTimeNs(requestTimeNs) {}
+    };
+
+    // helper function to return the output buffers to output
+    // streams. The function also optionally calls
+    // notify(ERROR_BUFFER).  Returns the list of buffers to hand back
+    // to streams in returnableBuffers.  Does not make any two-way
+    // binder calls, so suitable for use when critical locks are being
+    // held
+    void collectReturnableOutputBuffers(
             bool useHalBufManager,
             const std::set<int32_t> &halBufferManagedStreams,
             sp<NotificationListener> listener, // Only needed when outputSurfaces is not empty
             const camera_stream_buffer_t *outputBuffers,
             size_t numBuffers, nsecs_t timestamp,
             nsecs_t readoutTimestamp, bool requested, nsecs_t requestTimeNs,
-            SessionStatsBuilder& sessionStatsBuilder, bool timestampIncreasing = true,
+            SessionStatsBuilder& sessionStatsBuilder,
+            /*out*/ std::vector<BufferToReturn> *returnableBuffers,
+            bool timestampIncreasing = true,
             // The following arguments are only meant for surface sharing use case
             const SurfaceMap& outputSurfaces = SurfaceMap{},
             // Used to send buffer error callback when failing to return buffer
@@ -61,14 +95,24 @@
             ERROR_BUF_STRATEGY errorBufStrategy = ERROR_BUF_RETURN,
             int32_t transform = -1);
 
-    // helper function to return the output buffers to output streams, and
-    // remove the returned buffers from the inflight request's pending buffers
-    // vector.
-    void returnAndRemovePendingOutputBuffers(
+    // helper function to collect the output buffers ready to be
+    // returned to output streams, and to remove these buffers from
+    // the inflight request's pending buffers vector.  Does not make
+    // any two-way binder calls, so suitable for use when critical
+    // locks are being held
+    void collectAndRemovePendingOutputBuffers(
             bool useHalBufManager,
             const std::set<int32_t> &halBufferManagedStreams,
             sp<NotificationListener> listener, // Only needed when outputSurfaces is not empty
-            InFlightRequest& request, SessionStatsBuilder& sessionStatsBuilder);
+            InFlightRequest& request, SessionStatsBuilder& sessionStatsBuilder,
+            /*out*/ std::vector<BufferToReturn> *returnableBuffers);
+
+    // Actually return filled output buffers to the consumer to use, using the list
+    // provided by collectReturnableOutputBuffers / collectAndRemovePendingOutputBuffers
+    // Makes two-way binder calls to applications, so do not hold any critical locks when
+    // calling.
+    void finishReturningOutputBuffers(const std::vector<BufferToReturn> &returnableBuffers,
+            sp<NotificationListener> listener, SessionStatsBuilder& sessionStatsBuilder);
 
     // Camera3Device/Camera3OfflineSession internal states used in notify/processCaptureResult
     // callbacks
diff --git a/services/camera/libcameraservice/device3/Camera3OutputUtilsTemplated.h b/services/camera/libcameraservice/device3/Camera3OutputUtilsTemplated.h
index 2c30b15..aca7a67 100644
--- a/services/camera/libcameraservice/device3/Camera3OutputUtilsTemplated.h
+++ b/services/camera/libcameraservice/device3/Camera3OutputUtilsTemplated.h
@@ -345,10 +345,15 @@
             continue;
         }
         streamBuffer.stream = stream->asHalStream();
-        returnOutputBuffers(states.useHalBufManager, states.halBufManagedStreamIds,
+        std::vector<BufferToReturn> returnableBuffers{};
+        collectReturnableOutputBuffers(states.useHalBufManager, states.halBufManagedStreamIds,
                 /*listener*/nullptr, &streamBuffer, /*size*/1, /*timestamp*/ 0,
                 /*readoutTimestamp*/0, /*requested*/false, /*requestTimeNs*/0,
+                states.sessionStatsBuilder,
+                /*out*/&returnableBuffers);
+        finishReturningOutputBuffers(returnableBuffers, /*listener*/ nullptr,
                 states.sessionStatsBuilder);
+
     }
 }
 
diff --git a/services/camera/libcameraservice/device3/aidl/AidlCamera3OutputUtils.cpp b/services/camera/libcameraservice/device3/aidl/AidlCamera3OutputUtils.cpp
index 3fc070b..d9c8e57 100644
--- a/services/camera/libcameraservice/device3/aidl/AidlCamera3OutputUtils.cpp
+++ b/services/camera/libcameraservice/device3/aidl/AidlCamera3OutputUtils.cpp
@@ -319,10 +319,15 @@
                 sb.acquire_fence = -1;
                 sb.status = CAMERA_BUFFER_STATUS_ERROR;
             }
-            returnOutputBuffers(states.useHalBufManager,states.halBufManagedStreamIds, nullptr,
-                    streamBuffers.data(), numAllocatedBuffers, 0,
-                    0, false,
-                    0, states.sessionStatsBuilder);
+            std::vector<BufferToReturn> returnableBuffers{};
+            collectReturnableOutputBuffers(states.useHalBufManager, states.halBufManagedStreamIds,
+                    /*listener*/ nullptr,
+                    streamBuffers.data(), numAllocatedBuffers, /*timestamp*/ 0,
+                    /*readoutTimestamp*/ 0, /*requested*/ false,
+                    /*requestTimeNs*/ 0, states.sessionStatsBuilder,
+                    /*out*/ &returnableBuffers);
+            finishReturningOutputBuffers(returnableBuffers, /*listener*/ nullptr,
+                    states.sessionStatsBuilder);
             for (auto buf : newBuffers) {
                 states.bufferRecordsIntf.removeOneBufferCache(streamId, buf);
             }