From 000c3e44f3c449de255974965ca31b8ab7d3dc1a Mon Sep 17 00:00:00 2001
From: Ytai Ben-Tsvi <ytai@google.com>
Date: Thu, 9 Jan 2020 15:26:40 -0800
Subject: [PATCH] Support multiple error callbacks

Move from a single callback model to allow multiple registrations.
Created a separate mutex to guard the callback in order to simplify
the process of invoking the callbacks safely without holding the
main lock.

Change-Id: Id09aedda785e99b31c70cba1681a2ee392e9b06c
---
 media/libaudioclient/AudioSystem.cpp          | 33 ++++++++++++-------
 .../include/media/AudioSystem.h               | 20 +++++++++--
 2 files changed, 38 insertions(+), 15 deletions(-)

diff --git a/media/libaudioclient/AudioSystem.cpp b/media/libaudioclient/AudioSystem.cpp
index 941cf54d8d..e0ca07edab 100644
--- a/media/libaudioclient/AudioSystem.cpp
+++ b/media/libaudioclient/AudioSystem.cpp
@@ -36,10 +36,11 @@ namespace android {
 
 // client singleton for AudioFlinger binder interface
 Mutex AudioSystem::gLock;
+Mutex AudioSystem::gLockErrorCallbacks;
 Mutex AudioSystem::gLockAPS;
 sp<IAudioFlinger> AudioSystem::gAudioFlinger;
 sp<AudioSystem::AudioFlingerClient> AudioSystem::gAudioFlingerClient;
-audio_error_callback AudioSystem::gAudioErrorCallback = NULL;
+std::set<audio_error_callback> AudioSystem::gAudioErrorCallbacks;
 dynamic_policy_callback AudioSystem::gDynPolicyCallback = NULL;
 record_config_callback AudioSystem::gRecordConfigCallback = NULL;
 
@@ -63,9 +64,7 @@ const sp<IAudioFlinger> AudioSystem::get_audio_flinger()
             if (gAudioFlingerClient == NULL) {
                 gAudioFlingerClient = new AudioFlingerClient();
             } else {
-                if (gAudioErrorCallback) {
-                    gAudioErrorCallback(NO_ERROR);
-                }
+                reportError(NO_ERROR);
             }
             binder->linkToDeath(gAudioFlingerClient);
             gAudioFlinger = interface_cast<IAudioFlinger>(binder);
@@ -500,19 +499,16 @@ void AudioSystem::AudioFlingerClient::clearIoCache()
 
 void AudioSystem::AudioFlingerClient::binderDied(const wp<IBinder>& who __unused)
 {
-    audio_error_callback cb = NULL;
     {
         Mutex::Autolock _l(AudioSystem::gLock);
         AudioSystem::gAudioFlinger.clear();
-        cb = gAudioErrorCallback;
     }
 
     // clear output handles and stream to output map caches
     clearIoCache();
 
-    if (cb) {
-        cb(DEAD_OBJECT);
-    }
+    reportError(DEAD_OBJECT);
+
     ALOGW("AudioFlinger server died!");
 }
 
@@ -717,10 +713,23 @@ status_t AudioSystem::AudioFlingerClient::removeAudioDeviceCallback(
     return NO_ERROR;
 }
 
-/* static */ void AudioSystem::setErrorCallback(audio_error_callback cb)
+/* static */ uintptr_t AudioSystem::addErrorCallback(audio_error_callback cb)
 {
-    Mutex::Autolock _l(gLock);
-    gAudioErrorCallback = cb;
+    Mutex::Autolock _l(gLockErrorCallbacks);
+    gAudioErrorCallbacks.insert(cb);
+    return reinterpret_cast<uintptr_t>(cb);
+}
+
+/* static */ void AudioSystem::removeErrorCallback(uintptr_t cb) {
+    Mutex::Autolock _l(gLockErrorCallbacks);
+    gAudioErrorCallbacks.erase(reinterpret_cast<audio_error_callback>(cb));
+}
+
+/* static */ void AudioSystem::reportError(status_t err) {
+    Mutex::Autolock _l(gLockErrorCallbacks);
+    for (auto callback : gAudioErrorCallbacks) {
+      callback(err);
+    }
 }
 
 /*static*/ void AudioSystem::setDynPolicyCallback(dynamic_policy_callback cb)
diff --git a/media/libaudioclient/include/media/AudioSystem.h b/media/libaudioclient/include/media/AudioSystem.h
index c4b528e959..201acca401 100644
--- a/media/libaudioclient/include/media/AudioSystem.h
+++ b/media/libaudioclient/include/media/AudioSystem.h
@@ -27,6 +27,7 @@
 #include <media/IAudioFlingerClient.h>
 #include <media/IAudioPolicyServiceClient.h>
 #include <media/MicrophoneInfo.h>
+#include <set>
 #include <system/audio.h>
 #include <system/audio_effect.h>
 #include <system/audio_policy.h>
@@ -107,7 +108,16 @@ public:
     static status_t setParameters(const String8& keyValuePairs);
     static String8  getParameters(const String8& keys);
 
-    static void setErrorCallback(audio_error_callback cb);
+    // Registers an error callback. When this callback is invoked, it means all
+    // state implied by this interface has been reset.
+    // Returns a token that can be used for un-registering.
+    // Might block while callbacks are being invoked.
+    static uintptr_t addErrorCallback(audio_error_callback cb);
+
+    // Un-registers a callback previously added with addErrorCallback.
+    // Might block while callbacks are being invoked.
+    static void removeErrorCallback(uintptr_t cb);
+
     static void setDynPolicyCallback(dynamic_policy_callback cb);
     static void setRecordConfigCallback(record_config_callback);
 
@@ -560,15 +570,19 @@ private:
     static const sp<AudioFlingerClient> getAudioFlingerClient();
     static sp<AudioIoDescriptor> getIoDescriptor(audio_io_handle_t ioHandle);
 
+    // Invokes all registered error callbacks with the given error code.
+    static void reportError(status_t err);
+
     static sp<AudioFlingerClient> gAudioFlingerClient;
     static sp<AudioPolicyServiceClient> gAudioPolicyServiceClient;
     friend class AudioFlingerClient;
     friend class AudioPolicyServiceClient;
 
-    static Mutex gLock;      // protects gAudioFlinger and gAudioErrorCallback,
+    static Mutex gLock;      // protects gAudioFlinger
+    static Mutex gLockErrorCallbacks;      // protects gAudioErrorCallbacks
     static Mutex gLockAPS;   // protects gAudioPolicyService and gAudioPolicyServiceClient
     static sp<IAudioFlinger> gAudioFlinger;
-    static audio_error_callback gAudioErrorCallback;
+    static std::set<audio_error_callback> gAudioErrorCallbacks;
     static dynamic_policy_callback gDynPolicyCallback;
     static record_config_callback gRecordConfigCallback;