Introduce thread priorities for threads and handlerthreads.

app/src/androidTest/java/org/thoughtcrime/securesms/testing/InMemoryLogger.kt

@@ -1,5 +1,6 @@
 package org.thoughtcrime.securesms.testing
 
+import org.signal.core.util.ThreadUtil
 import org.signal.core.util.concurrent.SignalExecutors
 import org.signal.core.util.logging.Log
 import java.util.concurrent.CountDownLatch
@@ -13,7 +14,7 @@ typealias LogPredicate = (Entry) -> Boolean
  */
 class InMemoryLogger : Log.Logger() {
 
-  private val executor = SignalExecutors.newCachedSingleThreadExecutor("inmemory-logger")
+  private val executor = SignalExecutors.newCachedSingleThreadExecutor("inmemory-logger", ThreadUtil.PRIORITY_BACKGROUND_THREAD)
   private val predicates = mutableListOf<LogPredicate>()
   private val logEntries = mutableListOf<Entry>()
 

app/src/main/java/org/signal/glide/common/executor/FrameDecoderExecutor.java

@@ -8,6 +8,8 @@ package org.signal.glide.common.executor;
 import android.os.HandlerThread;
 import android.os.Looper;
 
+import org.signal.core.util.ThreadUtil;
+
 import java.util.ArrayList;
 import java.util.concurrent.atomic.AtomicInteger;
 
@@ -39,7 +41,7 @@ public class FrameDecoderExecutor {
     public Looper getLooper(int taskId) {
         int idx = taskId % sPoolNumber;
         if (idx >= mHandlerThreadGroup.size()) {
-            HandlerThread handlerThread = new HandlerThread("FrameDecoderExecutor-" + idx);
+            HandlerThread handlerThread = new HandlerThread("FrameDecoderExecutor-" + idx, ThreadUtil.PRIORITY_BACKGROUND_THREAD);
             handlerThread.start();
 
             mHandlerThreadGroup.add(handlerThread);

app/src/main/java/org/thoughtcrime/securesms/audio/AudioCodec.java

@@ -7,6 +7,7 @@ import android.media.MediaCodecInfo;
 import android.media.MediaFormat;
 import android.media.MediaRecorder;
 import android.os.ParcelFileDescriptor;
+import android.os.Process;
 
 import org.signal.core.util.StreamUtil;
 import org.signal.core.util.logging.Log;
@@ -65,6 +66,7 @@ public class AudioCodec implements Recorder {
     new Thread(new Runnable() {
       @Override
       public void run() {
+        Process.setThreadPriority(Process.THREAD_PRIORITY_AUDIO);
         MediaCodec.BufferInfo bufferInfo         = new MediaCodec.BufferInfo();
         byte[]                audioRecordData    = new byte[bufferSize];
         ByteBuffer[]          codecInputBuffers  = mediaCodec.getInputBuffers();

app/src/main/java/org/thoughtcrime/securesms/audio/AudioRecorder.java

@@ -9,6 +9,7 @@ import android.os.ParcelFileDescriptor;
 import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
 
+import org.signal.core.util.ThreadUtil;
 import org.signal.core.util.concurrent.SignalExecutors;
 import org.signal.core.util.logging.Log;
 import org.thoughtcrime.securesms.components.voice.VoiceNoteDraft;
@@ -25,7 +26,7 @@ public class AudioRecorder {
 
   private static final String TAG = Log.tag(AudioRecorder.class);
 
-  private static final ExecutorService executor = SignalExecutors.newCachedSingleThreadExecutor("signal-AudioRecorder");
+  private static final ExecutorService executor = SignalExecutors.newCachedSingleThreadExecutor("signal-AudioRecorder", ThreadUtil.PRIORITY_UI_BLOCKING_THREAD);
 
   private final Context                   context;
   private final AudioRecordingHandler     uiHandler;

app/src/main/java/org/thoughtcrime/securesms/dependencies/ApplicationDependencyProvider.java

@@ -9,6 +9,7 @@ import androidx.annotation.NonNull;
 import androidx.annotation.VisibleForTesting;
 
 import org.signal.core.util.Hex;
+import org.signal.core.util.ThreadUtil;
 import org.signal.core.util.concurrent.DeadlockDetector;
 import org.signal.core.util.concurrent.SignalExecutors;
 import org.signal.libsignal.zkgroup.profiles.ClientZkProfileOperations;
@@ -137,7 +138,7 @@ public class ApplicationDependencyProvider implements ApplicationDependencies.Pr
                                             signalWebSocket,
                                             Optional.of(new SecurityEventListener(context)),
                                             provideGroupsV2Operations(signalServiceConfiguration).getProfileOperations(),
-                                            SignalExecutors.newCachedBoundedExecutor("signal-messages", 1, 16, 30),
+                                            SignalExecutors.newCachedBoundedExecutor("signal-messages", ThreadUtil.PRIORITY_IMPORTANT_BACKGROUND_THREAD, 1, 16, 30),
                                             ByteUnit.KILOBYTES.toBytes(256),
                                             FeatureFlags.okHttpAutomaticRetry());
   }
@@ -373,7 +374,7 @@ public class ApplicationDependencyProvider implements ApplicationDependencies.Pr
 
   @Override
   public @NonNull DeadlockDetector provideDeadlockDetector() {
-    HandlerThread handlerThread = new HandlerThread("signal-DeadlockDetector");
+    HandlerThread handlerThread = new HandlerThread("signal-DeadlockDetector", ThreadUtil.PRIORITY_BACKGROUND_THREAD);
     handlerThread.start();
     return new DeadlockDetector(new Handler(handlerThread.getLooper()), TimeUnit.SECONDS.toMillis(5));
   }

app/src/main/java/org/thoughtcrime/securesms/emoji/JumboEmoji.kt

@@ -27,7 +27,7 @@ private val TAG = Log.tag(JumboEmoji::class.java)
  */
 object JumboEmoji {
 
-  private val executor = ThreadUtil.trace(SignalExecutors.newCachedSingleThreadExecutor("jumbo-emoji"))
+  private val executor = ThreadUtil.trace(SignalExecutors.newCachedSingleThreadExecutor("jumbo-emoji", ThreadUtil.PRIORITY_IMPORTANT_BACKGROUND_THREAD))
 
   const val MAX_JUMBOJI_COUNT = 5
 

app/src/main/java/org/thoughtcrime/securesms/jobmanager/InAppScheduler.java

@@ -7,6 +7,7 @@ import androidx.annotation.NonNull;
 
 import com.annimon.stream.Stream;
 
+import org.signal.core.util.ThreadUtil;
 import org.signal.core.util.logging.Log;
 
 import java.util.List;
@@ -30,7 +31,7 @@ class InAppScheduler implements Scheduler {
   private final Handler     handler;
 
   InAppScheduler(@NonNull JobManager jobManager) {
-    HandlerThread handlerThread = new HandlerThread("InAppScheduler");
+    HandlerThread handlerThread = new HandlerThread("InAppScheduler", ThreadUtil.PRIORITY_BACKGROUND_THREAD);
     handlerThread.start();
 
     this.jobManager = jobManager;

app/src/main/java/org/thoughtcrime/securesms/jobmanager/impl/DefaultExecutorFactory.java

@@ -1,7 +1,10 @@
 package org.thoughtcrime.securesms.jobmanager.impl;
 
+import android.os.Process;
+
 import androidx.annotation.NonNull;
 
+import org.signal.core.util.ThreadUtil;
 import org.thoughtcrime.securesms.jobmanager.ExecutorFactory;
 
 import java.util.concurrent.ExecutorService;
@@ -10,6 +13,11 @@ import java.util.concurrent.Executors;
 public class DefaultExecutorFactory implements ExecutorFactory {
   @Override
   public @NonNull ExecutorService newSingleThreadExecutor(@NonNull String name) {
-    return Executors.newSingleThreadExecutor(r -> new Thread(r, name));
+    return Executors.newSingleThreadExecutor(r -> new Thread(r, name) {
+      @Override public void run() {
+        Process.setThreadPriority(ThreadUtil.PRIORITY_BACKGROUND_THREAD);
+        super.run();
+      }
+    });
   }
 }

app/src/main/java/org/thoughtcrime/securesms/keyvalue/KeyValueStore.java

@@ -5,6 +5,7 @@ import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
 import androidx.annotation.WorkerThread;
 
+import org.signal.core.util.ThreadUtil;
 import org.signal.core.util.concurrent.SignalExecutors;
 import org.signal.core.util.logging.Log;
 import org.thoughtcrime.securesms.util.SignalUncaughtExceptionHandler;
@@ -35,7 +36,7 @@ public final class KeyValueStore implements KeyValueReader {
   private KeyValueDataSet dataSet;
 
   public KeyValueStore(@NonNull KeyValuePersistentStorage storage) {
-    this.executor = SignalExecutors.newCachedSingleThreadExecutor("signal-KeyValueStore");
+    this.executor = SignalExecutors.newCachedSingleThreadExecutor("signal-KeyValueStore", ThreadUtil.PRIORITY_BACKGROUND_THREAD);
     this.storage  = storage;
   }
 

app/src/main/java/org/thoughtcrime/securesms/mediasend/MediaUploadRepository.java

@@ -8,6 +8,7 @@ import androidx.annotation.WorkerThread;
 
 import com.annimon.stream.Stream;
 
+import org.signal.core.util.ThreadUtil;
 import org.signal.core.util.concurrent.SignalExecutors;
 import org.signal.core.util.logging.Log;
 import org.thoughtcrime.securesms.attachments.Attachment;
@@ -56,7 +57,7 @@ public class MediaUploadRepository {
   public MediaUploadRepository(@NonNull Context context) {
     this.context       = context;
     this.uploadResults = new LinkedHashMap<>();
-    this.executor      = SignalExecutors.newCachedSingleThreadExecutor("signal-MediaUpload");
+    this.executor      = SignalExecutors.newCachedSingleThreadExecutor("signal-MediaUpload", ThreadUtil.PRIORITY_IMPORTANT_BACKGROUND_THREAD);
   }
 
   public void startUpload(@NonNull Media media, @Nullable Recipient recipient) {

app/src/main/java/org/thoughtcrime/securesms/notifications/OptimizedMessageNotifier.java

@@ -9,6 +9,7 @@ import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
 
 import org.signal.core.util.ExceptionUtil;
+import org.signal.core.util.ThreadUtil;
 import org.signal.core.util.concurrent.SignalExecutors;
 import org.thoughtcrime.securesms.notifications.v2.DefaultMessageNotifier;
 import org.thoughtcrime.securesms.notifications.v2.ConversationId;
@@ -28,7 +29,7 @@ public class OptimizedMessageNotifier implements MessageNotifier {
 
   @MainThread
   public OptimizedMessageNotifier(@NonNull Application context) {
-    this.limiter                = new LeakyBucketLimiter(5, 1000, new Handler(SignalExecutors.getAndStartHandlerThread("signal-notifier").getLooper()));
+    this.limiter                = new LeakyBucketLimiter(5, 1000, new Handler(SignalExecutors.getAndStartHandlerThread("signal-notifier", ThreadUtil.PRIORITY_IMPORTANT_BACKGROUND_THREAD).getLooper()));
     this.defaultMessageNotifier = new DefaultMessageNotifier(context);
   }
 

app/src/main/java/org/thoughtcrime/securesms/providers/PartProvider.java

@@ -36,6 +36,7 @@ import androidx.annotation.Nullable;
 import androidx.annotation.RequiresApi;
 
 import org.signal.core.util.StreamUtil;
+import org.signal.core.util.ThreadUtil;
 import org.signal.core.util.concurrent.SignalExecutors;
 import org.signal.core.util.logging.Log;
 import org.thoughtcrime.securesms.BuildConfig;
@@ -201,7 +202,7 @@ public final class PartProvider extends BaseContentProvider {
   @RequiresApi(26)
   private ParcelFileDescriptor getParcelStreamProxyForAttachment(AttachmentId attachmentId) throws IOException {
     StorageManager storageManager = Objects.requireNonNull(getContext().getSystemService(StorageManager.class));
-    HandlerThread  thread         = SignalExecutors.getAndStartHandlerThread("storageservice-proxy");
+    HandlerThread  thread         = SignalExecutors.getAndStartHandlerThread("storageservice-proxy", ThreadUtil.PRIORITY_IMPORTANT_BACKGROUND_THREAD);
     Handler        handler        = new Handler(thread.getLooper());
 
     ParcelFileDescriptor parcelFileDescriptor = storageManager.openProxyFileDescriptor(ParcelFileDescriptor.MODE_READ_ONLY,

app/src/main/java/org/thoughtcrime/securesms/recipients/LiveRecipientCache.java

@@ -49,7 +49,7 @@ public final class LiveRecipientCache {
   private final AtomicBoolean                warmedUp;
 
   public LiveRecipientCache(@NonNull Context context) {
-    this(context, ThreadUtil.trace(new FilteredExecutor(SignalExecutors.newCachedBoundedExecutor("signal-recipients", 1, 4, 15), () -> !SignalDatabase.inTransaction())));
+    this(context, ThreadUtil.trace(new FilteredExecutor(SignalExecutors.newCachedBoundedExecutor("signal-recipients", ThreadUtil.PRIORITY_UI_BLOCKING_THREAD, 1, 4, 15), () -> !SignalDatabase.inTransaction())));
   }
 
   @VisibleForTesting

app/src/main/java/org/thoughtcrime/securesms/service/TimedEventManager.java

@@ -16,6 +16,7 @@ import androidx.annotation.Nullable;
 import androidx.annotation.WorkerThread;
 
 import org.signal.core.util.PendingIntentFlags;
+import org.signal.core.util.ThreadUtil;
 import org.signal.core.util.logging.Log;
 import org.thoughtcrime.securesms.util.ServiceUtil;
 
@@ -30,7 +31,7 @@ public abstract class TimedEventManager<E> {
   private final Handler     handler;
 
   public TimedEventManager(@NonNull Application application, @NonNull String threadName) {
-    HandlerThread handlerThread = new HandlerThread(threadName);
+    HandlerThread handlerThread = new HandlerThread(threadName, ThreadUtil.PRIORITY_BACKGROUND_THREAD);
     handlerThread.start();
 
     this.application = application;

app/src/main/java/org/thoughtcrime/securesms/util/LocalMetrics.kt

@@ -1,5 +1,6 @@
 package org.thoughtcrime.securesms.util
 
+import org.signal.core.util.ThreadUtil
 import org.signal.core.util.concurrent.SignalExecutors
 import org.signal.core.util.logging.Log
 import org.thoughtcrime.securesms.database.LocalMetricsDatabase
@@ -29,7 +30,7 @@ object LocalMetrics {
   private val eventsById: MutableMap<String, LocalMetricsEvent> = LRUCache(200)
   private val lastSplitTimeById: MutableMap<String, Long> = LRUCache(200)
 
-  private val executor: Executor = SignalExecutors.newCachedSingleThreadExecutor("signal-LocalMetrics")
+  private val executor: Executor = SignalExecutors.newCachedSingleThreadExecutor("signal-LocalMetrics", ThreadUtil.PRIORITY_BACKGROUND_THREAD)
   private val db: LocalMetricsDatabase by lazy { LocalMetricsDatabase.getInstance(ApplicationDependencies.getApplication()) }
 
   @JvmStatic

app/src/main/java/org/thoughtcrime/securesms/webrtc/audio/SignalAudioManager.kt

@@ -8,6 +8,7 @@ import android.media.AudioManager
 import android.media.SoundPool
 import android.net.Uri
 import android.os.Build
+import org.signal.core.util.ThreadUtil
 import org.signal.core.util.concurrent.SignalExecutors
 import org.signal.core.util.logging.Log
 import org.thoughtcrime.securesms.R
@@ -21,7 +22,7 @@ private val TAG = Log.tag(SignalAudioManager::class.java)
 
 sealed class SignalAudioManager(protected val context: Context, protected val eventListener: EventListener?) {
 
-  private var commandAndControlThread = SignalExecutors.getAndStartHandlerThread("call-audio")
+  private var commandAndControlThread = SignalExecutors.getAndStartHandlerThread("call-audio", ThreadUtil.PRIORITY_IMPORTANT_BACKGROUND_THREAD)
   protected val handler = SignalAudioHandler(commandAndControlThread.looper)
 
   protected var state: State = State.UNINITIALIZED

core-util/src/main/java/org/signal/core/util/ThreadUtil.java

@@ -2,6 +2,7 @@ package org.signal.core.util;
 
 import android.os.Handler;
 import android.os.Looper;
+import android.os.Process;
 
 import androidx.annotation.NonNull;
 import androidx.annotation.VisibleForTesting;
@@ -18,6 +19,20 @@ import java.util.concurrent.ExecutorService;
  */
 public final class ThreadUtil {
 
+  /**
+   * Default background thread priority.
+   */
+  public static final int PRIORITY_BACKGROUND_THREAD = Process.THREAD_PRIORITY_BACKGROUND;
+  /**
+   * Important background thread priority. This is slightly lower priority than the UI thread. Use for critical work that should run as fast as
+   * possible, but shouldn't block the UI (e.g. message sends)
+   */
+  public static final int PRIORITY_IMPORTANT_BACKGROUND_THREAD = Process.THREAD_PRIORITY_DEFAULT + Process.THREAD_PRIORITY_LESS_FAVORABLE;
+  /**
+   * As important as the UI thread. Use for absolutely critical UI blocking tasks/threads. For example fetching data for display in a recyclerview, or
+   * anything that will block UI.
+   */
+  public static final int PRIORITY_UI_BLOCKING_THREAD = Process.THREAD_PRIORITY_DEFAULT;
   private static volatile Handler handler;
 
   @VisibleForTesting

core-util/src/main/java/org/signal/core/util/concurrent/SignalExecutors.java

@@ -1,6 +1,7 @@
 package org.signal.core.util.concurrent;
 
 import android.os.HandlerThread;
+import android.os.Process;
 
 import androidx.annotation.NonNull;
 
@@ -17,15 +18,20 @@ import java.util.concurrent.atomic.AtomicInteger;
 
 public final class SignalExecutors {
 
-  public static final ExecutorService UNBOUNDED  = ThreadUtil.trace(Executors.newCachedThreadPool(new NumberedThreadFactory("signal-unbounded")));
+  public static final ExecutorService UNBOUNDED  = ThreadUtil.trace(Executors.newCachedThreadPool(new NumberedThreadFactory("signal-unbounded", ThreadUtil.PRIORITY_BACKGROUND_THREAD)));
-  public static final ExecutorService BOUNDED    = ThreadUtil.trace(Executors.newFixedThreadPool(4, new NumberedThreadFactory("signal-bounded")));
+  public static final ExecutorService BOUNDED    = ThreadUtil.trace(Executors.newFixedThreadPool(4, new NumberedThreadFactory("signal-bounded", ThreadUtil.PRIORITY_BACKGROUND_THREAD)));
-  public static final ExecutorService SERIAL     = ThreadUtil.trace(Executors.newSingleThreadExecutor(new NumberedThreadFactory("signal-serial")));
+  public static final ExecutorService SERIAL     = ThreadUtil.trace(Executors.newSingleThreadExecutor(new NumberedThreadFactory("signal-serial", ThreadUtil.PRIORITY_BACKGROUND_THREAD)));
-  public static final ExecutorService BOUNDED_IO = ThreadUtil.trace(newCachedBoundedExecutor("signal-io-bounded", 1, 32, 30));
+  public static final ExecutorService BOUNDED_IO = ThreadUtil.trace(newCachedBoundedExecutor("signal-io-bounded", ThreadUtil.PRIORITY_IMPORTANT_BACKGROUND_THREAD, 1, 32, 30));
 
   private SignalExecutors() {}
 
-  public static ExecutorService newCachedSingleThreadExecutor(final String name) {
+  public static ExecutorService newCachedSingleThreadExecutor(final String name, int priority) {
-    ThreadPoolExecutor executor = new ThreadPoolExecutor(1, 1, 15, TimeUnit.SECONDS, new LinkedBlockingQueue<>(), r -> new Thread(r, name));
+    ThreadPoolExecutor executor = new ThreadPoolExecutor(1, 1, 15, TimeUnit.SECONDS, new LinkedBlockingQueue<>(), r -> new Thread(r, name) {
+      @Override public void run() {
+        Process.setThreadPriority(priority);
+        super.run();
+      }
+    });
     executor.allowCoreThreadTimeOut(true);
     return executor;
   }
@@ -41,7 +47,7 @@ public final class SignalExecutors {
    * So we make a queue that will always return false if it's non-empty to ensure new threads get
    * created. Then, if a task gets rejected, we simply add it to the queue.
    */
-  public static ExecutorService newCachedBoundedExecutor(final String name, int minThreads, int maxThreads, int timeoutSeconds) {
+  public static ExecutorService newCachedBoundedExecutor(final String name, int priority, int minThreads, int maxThreads, int timeoutSeconds) {
     ThreadPoolExecutor threadPool = new ThreadPoolExecutor(minThreads,
                                                            maxThreads,
                                                            timeoutSeconds,
@@ -55,7 +61,7 @@ public final class SignalExecutors {
                                                                  return false;
                                                                }
                                                              }
-                                                           }, new NumberedThreadFactory(name));
+                                                           }, new NumberedThreadFactory(name, priority));
 
     threadPool.setRejectedExecutionHandler((runnable, executor) -> {
       try {
@@ -73,28 +79,36 @@ public final class SignalExecutors {
    * which processor work in FIFO order.
    */
   public static ExecutorService newFixedLifoThreadExecutor(String name, int minThreads, int maxThreads) {
-    return new ThreadPoolExecutor(minThreads, maxThreads, 0, TimeUnit.MILLISECONDS, new LinkedBlockingLifoQueue<>(), new NumberedThreadFactory(name));
+    return new ThreadPoolExecutor(minThreads, maxThreads, 0, TimeUnit.MILLISECONDS, new LinkedBlockingLifoQueue<>(), new NumberedThreadFactory(name, ThreadUtil.PRIORITY_BACKGROUND_THREAD));
   }
 
-  public static HandlerThread getAndStartHandlerThread(@NonNull String name) {
+  public static HandlerThread getAndStartHandlerThread(@NonNull String name, int priority) {
-    HandlerThread handlerThread = new HandlerThread(name);
+    HandlerThread handlerThread = new HandlerThread(name, priority);
     handlerThread.start();
     return handlerThread;
   }
 
   private static class NumberedThreadFactory implements ThreadFactory {
 
+    private final int           priority;
     private final String        baseName;
     private final AtomicInteger counter;
 
-    NumberedThreadFactory(@NonNull String baseName) {
+    NumberedThreadFactory(@NonNull String baseName, int priority) {
+      this.priority = priority;
       this.baseName = baseName;
       this.counter  = new AtomicInteger();
     }
 
     @Override
     public Thread newThread(@NonNull Runnable r) {
-      return new Thread(r, baseName + "-" + counter.getAndIncrement());
+      return new Thread(r, baseName + "-" + counter.getAndIncrement()) {
+        @Override
+        public void run() {
+          Process.setThreadPriority(priority);
+          super.run();
+        }
+      };
     }
   }
 }

device-transfer/lib/src/main/java/org/signal/devicetransfer/DeviceTransferClient.java

@@ -14,6 +14,7 @@ import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
 
 import org.greenrobot.eventbus.EventBus;
+import org.signal.core.util.ThreadUtil;
 import org.signal.core.util.concurrent.SignalExecutors;
 import org.signal.core.util.logging.Log;
 
@@ -80,7 +81,7 @@ final class DeviceTransferClient implements Handler.Callback {
     this.context                 = context;
     this.clientTask              = clientTask;
     this.shutdownCallback        = shutdownCallback;
-    this.commandAndControlThread = SignalExecutors.getAndStartHandlerThread("client-cnc");
+    this.commandAndControlThread = SignalExecutors.getAndStartHandlerThread("client-cnc", ThreadUtil.PRIORITY_IMPORTANT_BACKGROUND_THREAD);
     this.handler                 = new Handler(commandAndControlThread.getLooper(), this);
     this.autoRestart             = () -> {
       Log.i(TAG, "Restarting WiFi Direct since we haven't found anything yet and it could be us.");

device-transfer/lib/src/main/java/org/signal/devicetransfer/DeviceTransferServer.java

@@ -14,6 +14,7 @@ import androidx.annotation.NonNull;
 import androidx.annotation.Nullable;
 
 import org.greenrobot.eventbus.EventBus;
+import org.signal.core.util.ThreadUtil;
 import org.signal.core.util.concurrent.SignalExecutors;
 import org.signal.core.util.logging.Log;
 import org.signal.devicetransfer.SelfSignedIdentity.SelfSignedKeys;
@@ -70,7 +71,7 @@ final class DeviceTransferServer implements Handler.Callback {
     this.context                 = context;
     this.serverTask              = serverTask;
     this.shutdownCallback        = shutdownCallback;
-    this.commandAndControlThread = SignalExecutors.getAndStartHandlerThread("server-cnc");
+    this.commandAndControlThread = SignalExecutors.getAndStartHandlerThread("server-cnc", ThreadUtil.PRIORITY_IMPORTANT_BACKGROUND_THREAD);
     this.handler                 = new Handler(commandAndControlThread.getLooper(), this);
   }
 

device-transfer/lib/src/main/java/org/signal/devicetransfer/WifiDirect.java

@@ -92,7 +92,7 @@ public final class WifiDirect {
 
   WifiDirect(@NonNull Context context) {
     this.context                    = context.getApplicationContext();
-    this.wifiDirectCallbacksHandler = SignalExecutors.getAndStartHandlerThread("wifi-direct-cb");
+    this.wifiDirectCallbacksHandler = SignalExecutors.getAndStartHandlerThread("wifi-direct-cb", ThreadUtil.PRIORITY_IMPORTANT_BACKGROUND_THREAD);
   }
 
   /**

paging/lib/src/main/java/org/signal/paging/FixedSizePagingController.java

@@ -2,6 +2,7 @@ package org.signal.paging;
 
 import androidx.annotation.NonNull;
 
+import org.signal.core.util.ThreadUtil;
 import org.signal.core.util.concurrent.SignalExecutors;
 import org.signal.core.util.logging.Log;
 
@@ -23,7 +24,7 @@ class FixedSizePagingController<Key, Data> implements PagingController<Key> {
 
   private static final String TAG = Log.tag(FixedSizePagingController.class);
 
-  private static final Executor FETCH_EXECUTOR = SignalExecutors.newCachedSingleThreadExecutor("signal-FixedSizePagingController");
+  private static final Executor FETCH_EXECUTOR = SignalExecutors.newCachedSingleThreadExecutor("signal-FixedSizePagingController", ThreadUtil.PRIORITY_UI_BLOCKING_THREAD);
   private static final boolean  DEBUG          = false;
 
   private final PagedDataSource<Key, Data>  dataSource;