media.log: dump all readers with dumpsys option "r"

Bug: 37153050
Test: builds OK, "dumpsys media.log r" shows all readers
Change-Id: I584dbbeb0532b019441f7aeb4793a9f4e3f6bdda
diff --git a/services/medialog/MediaLogService.cpp b/services/medialog/MediaLogService.cpp
index aaf1018..a5512e1 100644
--- a/services/medialog/MediaLogService.cpp
+++ b/services/medialog/MediaLogService.cpp
@@ -26,7 +26,7 @@
 
 namespace android {
 
-// static const char kDeadlockedString[] = "MediaLogService may be deadlocked\n";
+ static const char kDeadlockedString[] = "MediaLogService may be deadlocked\n";
 MediaLogService::MediaLogService() :
     BnMediaLogService(),
     mMergerShared((NBLog::Shared*) malloc(NBLog::Timeline::sharedSize(kMergeBufferSize))),
@@ -99,35 +99,38 @@
         return NO_ERROR;
     }
 
-#if 0
-    Vector<NBLog::NamedReader> namedReaders;
-    {
-        bool locked = dumpTryLock(mLock);
+    if (args.size() > 0) {
+        const String8 arg0(args[0]);
+        if (!strcmp(arg0.string(), "-r")) {
+            // needed because mNamedReaders is protected by mLock
+            bool locked = dumpTryLock(mLock);
 
-        // failed to lock - MediaLogService is probably deadlocked
-        if (!locked) {
-            String8 result(kDeadlockedString);
-            if (fd >= 0) {
-                write(fd, result.string(), result.size());
-            } else {
-                ALOGW("%s:", result.string());
+            // failed to lock - MediaLogService is probably deadlocked
+            if (!locked) {
+                String8 result(kDeadlockedString);
+                if (fd >= 0) {
+                    write(fd, result.string(), result.size());
+                } else {
+                    ALOGW("%s:", result.string());
+                }
+                // TODO should we instead proceed to mMergeReader.dump? does it need lock?
+                return NO_ERROR;
             }
-            return NO_ERROR;
-        }
-            // namedReaders = mNamedReaders;
-            // for (size_t i = 0; i < namedReaders.size(); i++) {
-            //     const NBLog::NamedReader& namedReader = namedReaders[i];
-            //     if (fd >= 0) {
-            //         dprintf(fd, "\n%s:\n", namedReader.name());
-            //     } else {
-            //         ALOGI("%s:", namedReader.name());
-            //     }
-            //     namedReader.reader()->dump(fd, 0 /*indent*/);
-            // }
 
-        mLock.unlock();
+            for (const auto& namedReader : mNamedReaders) {
+                if (fd >= 0) {
+                    dprintf(fd, "\n%s:\n", namedReader.name());
+                } else {
+                    ALOGI("%s:", namedReader.name());
+                }
+                // TODO This code is for testing, remove it when done
+                // namedReader.reader()->dump(fd, 0 /*indent*/);
+            }
+
+            mLock.unlock();
+        }
     }
-#endif
+
     // FIXME request merge to make sure log is up to date
     mMergeReader.dump(fd);
     return NO_ERROR;