commit d52a28ca2c19db7d10bc6c4639a8bd78e1afd5f1
author Eric Laurent <elaurent@google.com> Fri Aug 21 17:10:39 2020 -0700
committer Eric Laurent <elaurent@google.com> Tue Aug 25 13:33:12 2020 -0700
tree c687eda00e2c45823cdb1857c64ad48b67578819
parent 615364792b6fe07869c685e4bccbf7837e1ba97b

audio flinger: handle race condition in AudioRecord creation

A rare race condition can cause a failure to create an AudioRecord if
two creation requests are processed concurrently and thread preemption happens
at a specific time within the sequence between audioflinger and
audio policy manager.

This CL implements a retry mechanism on client side when this particular failure
is detected.

Bug: 161656190
Test: Regression tests for audio capture use cases.
Test: CTS tests for AudiRecord
Change-Id: I155ee4899baeec21e10a1141cb9e323cbc8aa23b

services/audioflinger/AudioFlinger.cpp

diff --git a/services/audioflinger/AudioFlinger.cpp b/services/audioflinger/AudioFlinger.cpp
index 34bdac5..36dc1db 100644
--- a/services/audioflinger/AudioFlinger.cpp
+++ b/services/audioflinger/AudioFlinger.cpp
@@ -2071,8 +2071,8 @@
         Mutex::Autolock _l(mLock);
         RecordThread *thread = checkRecordThread_l(output.inputId);
         if (thread == NULL) {
-            ALOGE("createRecord() checkRecordThread_l failed, input handle %d", output.inputId);
-            lStatus = BAD_VALUE;
+            ALOGW("createRecord() checkRecordThread_l failed, input handle %d", output.inputId);
+            lStatus = FAILED_TRANSACTION;
             goto Exit;
         }
 

services/audioflinger/Threads.cpp

diff --git a/services/audioflinger/Threads.cpp b/services/audioflinger/Threads.cpp
index affc09e..75f0743 100644
--- a/services/audioflinger/Threads.cpp
+++ b/services/audioflinger/Threads.cpp
@@ -7911,7 +7911,8 @@
         AutoMutex lock(mLock);
         if (recordTrack->isInvalid()) {
             recordTrack->clearSyncStartEvent();
-            return INVALID_OPERATION;
+            ALOGW("%s track %d: invalidated before startInput", __func__, recordTrack->portId());
+            return DEAD_OBJECT;
         }
         if (mActiveTracks.indexOf(recordTrack) >= 0) {
             if (recordTrack->mState == TrackBase::PAUSING) {
@@ -7941,7 +7942,8 @@
                     recordTrack->mState = TrackBase::STARTING_2;
                     // STARTING_2 forces destroy to call stopInput.
                 }
-                return INVALID_OPERATION;
+                ALOGW("%s track %d: invalidated after startInput", __func__, recordTrack->portId());
+                return DEAD_OBJECT;
             }
             if (recordTrack->mState != TrackBase::STARTING_1) {
                 ALOGW("%s(%d): unsynchronized mState:%d change",

services/audioflinger/Tracks.cpp

diff --git a/services/audioflinger/Tracks.cpp b/services/audioflinger/Tracks.cpp
index c92bce5..ed285da 100644
--- a/services/audioflinger/Tracks.cpp
+++ b/services/audioflinger/Tracks.cpp
@@ -2229,7 +2229,8 @@
         RecordThread *recordThread = (RecordThread *)thread.get();
         return recordThread->start(this, event, triggerSession);
     } else {
-        return BAD_VALUE;
+        ALOGW("%s track %d: thread was destroyed", __func__, portId());
+        return DEAD_OBJECT;
     }
 }