AudioFlinger: add specific mutex for client lists

Add a specific mutex to protect access to mClients and
mNotificationClients lists. This avoids locking the main AudioFlinger
mutex from inside thread loops and allows not to worry about
cross deadlocks when sending a config event with status reply while
keeping the ThreadBase or AudioFlinger mutex locked.
As a way of consequence, remove notification client list passed to
processConfigEvents_l() and audioConfigChanged() as the list
can now be accessed by locking client mutex only.

Change-Id: I228022204b6709a8bb60cc96d9514a6ffe59b62e

1 files changed, 8 insertions, 9 deletions

diff --git a/services/audioflinger/AudioFlinger.h b/services/audioflinger/AudioFlinger.h
index 894bd35..c1d4c08 100644
--- a/services/audioflinger/AudioFlinger.h
+++ b/services/audioflinger/AudioFlinger.h
@@ -453,11 +453,7 @@ private:
               // no range check, doesn't check per-thread stream volume, AudioFlinger::mLock held
               float streamVolume_l(audio_stream_type_t stream) const
                                 { return mStreamTypes[stream].volume; }
-              void audioConfigChanged_l(const DefaultKeyedVector< pid_t,sp<NotificationClient> >&
-                                           notificationClients,
-                                        int event,
-                                        audio_io_handle_t ioHandle,
-                                        const void *param2);
+              void audioConfigChanged(int event, audio_io_handle_t ioHandle, const void *param2);
 
               // Allocate an audio_io_handle_t, session ID, effect ID, or audio_module_handle_t.
               // They all share the same ID space, but the namespaces are actually independent
@@ -482,8 +478,6 @@ private:
 
                 void        removeClient_l(pid_t pid);
                 void        removeNotificationClient(pid_t pid);
-                DefaultKeyedVector< pid_t,sp<NotificationClient> > notificationClients() {
-                                        Mutex::Autolock _l(mLock); return mNotificationClients; }
                 bool isNonOffloadableGlobalEffectEnabled_l();
                 void onNonOffloadableGlobalEffectEnable();
 
@@ -553,7 +547,11 @@ private:
     };
 
     mutable     Mutex                               mLock;
-
+                // protects mClients and mNotificationClients.
+                // must be locked after mLock and ThreadBase::mLock if both must be locked
+                // avoids acquiring AudioFlinger::mLock from inside thread loop.
+    mutable     Mutex                               mClientLock;
+                // protected by mClientLock
                 DefaultKeyedVector< pid_t, wp<Client> >     mClients;   // see ~Client()
 
                 mutable     Mutex                   mHardwareLock;
@@ -602,6 +600,7 @@ private:
 
                 DefaultKeyedVector< audio_io_handle_t, sp<RecordThread> >    mRecordThreads;
 
+                // protected by mClientLock
                 DefaultKeyedVector< pid_t, sp<NotificationClient> >    mNotificationClients;
 
                 volatile int32_t                    mNextUniqueId;  // updated by android_atomic_inc
@@ -622,7 +621,7 @@ private:
                                                              // to be created
 
 private:
-    sp<Client>  registerPid_l(pid_t pid);    // always returns non-0
+    sp<Client>  registerPid(pid_t pid);    // always returns non-0
 
     // for use from destructor
     status_t    closeOutput_nonvirtual(audio_io_handle_t output);