Fix deadlock with nested calls to runBlocking.

Fixes #14460

app/src/main/java/org/thoughtcrime/securesms/backup/v2/ArchiveDatabaseExecutor.kt

@@ -5,8 +5,7 @@
 
 package org.thoughtcrime.securesms.backup.v2
 
-import org.signal.core.util.ThreadUtil
-import org.signal.core.util.concurrent.SignalExecutors
+import androidx.annotation.VisibleForTesting
 import org.thoughtcrime.securesms.dependencies.AppDependencies
 import org.thoughtcrime.securesms.util.ThrottledDebouncer
 import java.util.concurrent.ExecutionException
@@ -19,7 +18,10 @@ import kotlin.time.Duration.Companion.seconds
  */
 object ArchiveDatabaseExecutor {
 
-  val executor = Executors.newSingleThreadExecutor(SignalExecutors.NumberedThreadFactory("archive-db", ThreadUtil.PRIORITY_IMPORTANT_BACKGROUND_THREAD))
+  @VisibleForTesting
+  const val THREAD_NAME = "archive-db"
+
+  private val executor = Executors.newSingleThreadExecutor { Thread(it, THREAD_NAME) }
 
   /**
    * By default, downloading/uploading an attachment wants to notify a bunch of database observation listeners. This slams the observer so hard that other
@@ -39,6 +41,10 @@ object ArchiveDatabaseExecutor {
   }
 
   fun <T> runBlocking(block: () -> T): T {
+    if (Thread.currentThread().name.equals(THREAD_NAME)) {
+      return block()
+    }
+
     return try {
       executor.submit(block).get()
     } catch (e: ExecutionException) {

app/src/main/java/org/thoughtcrime/securesms/jobs/UploadAttachmentToArchiveJob.kt

@@ -360,10 +360,8 @@ class UploadAttachmentToArchiveJob private constructor(
   }
 
   private fun setArchiveTransferStateWithDelayedNotification(attachmentId: AttachmentId, transferState: AttachmentTable.ArchiveTransferState) {
-    ArchiveDatabaseExecutor.runBlocking {
-      SignalDatabase.attachments.setArchiveTransferState(attachmentId, transferState, notify = false)
-      ArchiveDatabaseExecutor.throttledNotifyAttachmentObservers()
-    }
+    SignalDatabase.attachments.setArchiveTransferState(attachmentId, transferState, notify = false)
+    ArchiveDatabaseExecutor.throttledNotifyAttachmentObservers()
   }
 
   class Factory : Job.Factory<UploadAttachmentToArchiveJob> {

app/src/test/java/org/thoughtcrime/securesms/backup/v2/ArchiveDatabaseExecutorTest.kt

@@ -0,0 +1,66 @@
+package org.thoughtcrime.securesms.backup.v2
+
+import android.app.Application
+import assertk.assertThat
+import assertk.assertions.isEqualTo
+import assertk.assertions.isTrue
+import org.junit.Test
+import org.junit.runner.RunWith
+import org.robolectric.RobolectricTestRunner
+import org.robolectric.annotation.Config
+import java.util.concurrent.CountDownLatch
+import java.util.concurrent.TimeUnit
+import java.util.concurrent.atomic.AtomicBoolean
+import java.util.concurrent.atomic.AtomicReference
+
+@RunWith(RobolectricTestRunner::class)
+@Config(manifest = Config.NONE, application = Application::class)
+class ArchiveDatabaseExecutorTest {
+
+  @Test
+  fun `runBlocking returns the result of the block`() {
+    val result = ArchiveDatabaseExecutor.runBlocking {
+      42
+    }
+
+    assertThat(result).isEqualTo(42)
+  }
+
+  @Test
+  fun `nested runBlocking calls do not deadlock`() {
+    val completed = AtomicBoolean(false)
+    val result = AtomicReference<String>()
+    val latch = CountDownLatch(1)
+
+    Thread {
+      try {
+        val r = ArchiveDatabaseExecutor.runBlocking {
+          ArchiveDatabaseExecutor.runBlocking {
+            ArchiveDatabaseExecutor.runBlocking {
+              "nested-result"
+            }
+          }
+        }
+        result.set(r)
+        completed.set(true)
+      } finally {
+        latch.countDown()
+      }
+    }.start()
+
+    val finishedInTime = latch.await(5, TimeUnit.SECONDS)
+
+    assertThat(finishedInTime).isTrue()
+    assertThat(completed.get()).isTrue()
+    assertThat(result.get()).isEqualTo("nested-result")
+  }
+
+  @Test
+  fun `runBlocking executes on archive-db thread`() {
+    val threadName = ArchiveDatabaseExecutor.runBlocking {
+      Thread.currentThread().name
+    }
+
+    assertThat(threadName).isEqualTo(ArchiveDatabaseExecutor.THREAD_NAME)
+  }
+}