Add error messages to send-trim-memory

Fixes: 23006305
Test: manual, adb shell am send-trim-memory
Change-Id: Iae5607ea9abf0ffa5b5276a6540afb0dc6aa31f5

2 files changed, 18 insertions, 15 deletions

diff --git a/cmds/am/src/com/android/commands/am/Am.java b/cmds/am/src/com/android/commands/am/Am.java
index d6c00589e7c2..91334bd87296 100644
--- a/cmds/am/src/com/android/commands/am/Am.java
+++ b/cmds/am/src/com/android/commands/am/Am.java
@@ -2523,8 +2523,7 @@ public class Am extends BaseCommand {
                 return;
         }
         if (!mAm.setProcessMemoryTrimLevel(proc, userId, level)) {
-            System.err.println("Error: Failure to set the level - probably Unknown Process: " +
-                               proc);
+            System.err.println("Unknown error: failed to set trim level");
         }
     }
 
diff --git a/services/core/java/com/android/server/am/ActivityManagerService.java b/services/core/java/com/android/server/am/ActivityManagerService.java
index 324d60241146..0e957b9f30a7 100644
--- a/services/core/java/com/android/server/am/ActivityManagerService.java
+++ b/services/core/java/com/android/server/am/ActivityManagerService.java
@@ -4068,25 +4068,29 @@ public final class ActivityManagerService extends ActivityManagerNative
     }
 
     @Override
-    public boolean setProcessMemoryTrimLevel(String process, int userId, int level) {
+    public boolean setProcessMemoryTrimLevel(String process, int userId, int level)
+            throws RemoteException {
         synchronized (this) {
             final ProcessRecord app = findProcessLocked(process, userId, "setProcessMemoryTrimLevel");
             if (app == null) {
-                return false;
+                throw new IllegalArgumentException("Unknown process: " + process);
             }
-            if (app.trimMemoryLevel < level && app.thread != null &&
-                    (level < ComponentCallbacks2.TRIM_MEMORY_UI_HIDDEN ||
-                            app.curProcState >= ActivityManager.PROCESS_STATE_IMPORTANT_BACKGROUND)) {
-                try {
-                    app.thread.scheduleTrimMemory(level);
-                    app.trimMemoryLevel = level;
-                    return true;
-                } catch (RemoteException e) {
-                    // Fallthrough to failure case.
-                }
+            if (app.thread == null) {
+                throw new IllegalArgumentException("Process has no app thread");
             }
+            if (app.trimMemoryLevel >= level) {
+                throw new IllegalArgumentException(
+                        "Unable to set a higher trim level than current level");
+            }
+            if (!(level < ComponentCallbacks2.TRIM_MEMORY_UI_HIDDEN ||
+                    app.curProcState >= ActivityManager.PROCESS_STATE_IMPORTANT_BACKGROUND)) {
+                throw new IllegalArgumentException("Unable to set a background trim level "
+                    + "on a foreground process");
+            }
+            app.thread.scheduleTrimMemory(level);
+            app.trimMemoryLevel = level;
+            return true;
         }
-        return false;
     }
 
     private void dispatchProcessesChanged() {