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Commit 88bd61e3 authored by Glenn Kasten's avatar Glenn Kasten Committed by Android (Google) Code Review
Browse files

Merge "Reduce rollovers of unique ID generator" into nyc-dev

parents 3f5eba44 d2e67e1e

services/audioflinger/AudioFlinger.cpp

+22 −6
Original line number Diff line number Diff line
@@ -176,7 +176,7 @@ AudioFlinger::AudioFlinger() 
      mHardwareStatus(AUDIO_HW_IDLE),

      mMasterVolume(1.0f),

      mMasterMute(false),

      mNextUniqueId(AUDIO_UNIQUE_ID_USE_MAX),   // zero has a special meaning, so unavailable

      // mNextUniqueId(AUDIO_UNIQUE_ID_USE_MAX),

      mMode(AUDIO_MODE_INVALID),

      mBtNrecIsOff(false),

      mIsLowRamDevice(true),
@@ -184,6 +184,12 @@ AudioFlinger::AudioFlinger() 
      mGlobalEffectEnableTime(0),

      mSystemReady(false)

{

    // unsigned instead of audio_unique_id_use_t, because ++ operator is unavailable for enum

    for (unsigned use = AUDIO_UNIQUE_ID_USE_UNSPECIFIED; use < AUDIO_UNIQUE_ID_USE_MAX; use++) {

        // zero ID has a special meaning, so unavailable

        mNextUniqueIds[use] = AUDIO_UNIQUE_ID_USE_MAX;

    }



    getpid_cached = getpid();

    const bool doLog = property_get_bool("ro.test_harness", false);

    if (doLog) {
@@ -2440,14 +2446,24 @@ AudioFlinger::RecordThread *AudioFlinger::checkRecordThread_l(audio_io_handle_t 


audio_unique_id_t AudioFlinger::nextUniqueId(audio_unique_id_use_t use)

{

    int32_t base = android_atomic_add(AUDIO_UNIQUE_ID_USE_MAX, &mNextUniqueId);

    // We have no way of recovering from wraparound

    LOG_ALWAYS_FATAL_IF(base == 0, "unique ID overflow");

    // This is the internal API, so it is OK to assert on bad parameter.

    LOG_ALWAYS_FATAL_IF((unsigned) use >= (unsigned) AUDIO_UNIQUE_ID_USE_MAX);

    const int maxRetries = use == AUDIO_UNIQUE_ID_USE_SESSION ? 3 : 1;

    for (int retry = 0; retry < maxRetries; retry++) {

        // The cast allows wraparound from max positive to min negative instead of abort

        uint32_t base = (uint32_t) atomic_fetch_add_explicit(&mNextUniqueIds[use],

                (uint_fast32_t) AUDIO_UNIQUE_ID_USE_MAX, memory_order_acq_rel);

        ALOG_ASSERT(audio_unique_id_get_use(base) == AUDIO_UNIQUE_ID_USE_UNSPECIFIED);

        // allow wrap by skipping 0 and -1 for session ids

        if (!(base == 0 || base == (~0u & ~AUDIO_UNIQUE_ID_USE_MASK))) {

            ALOGW_IF(retry != 0, "unique ID overflow for use %d", use);

            return (audio_unique_id_t) (base | use);

        }

    }

    // We have no way of recovering from wraparound

    LOG_ALWAYS_FATAL("unique ID overflow for use %d", use);

    // TODO Use a floor after wraparound.  This may need a mutex.

}



AudioFlinger::PlaybackThread *AudioFlinger::primaryPlaybackThread_l() const

{

services/audioflinger/AudioFlinger.h

+2 −3
Original line number Diff line number Diff line
@@ -679,9 +679,8 @@ private: 
                // protected by mClientLock

                DefaultKeyedVector< pid_t, sp<NotificationClient> >    mNotificationClients;



                volatile int32_t                    mNextUniqueId;  // updated by android_atomic_inc

                // nextUniqueId() returns uint32_t, but this is declared int32_t

                // because the atomic operations require an int32_t

                // updated by atomic_fetch_add_explicit

                volatile atomic_uint_fast32_t       mNextUniqueIds[AUDIO_UNIQUE_ID_USE_MAX];



                audio_mode_t                        mMode;

                bool                                mBtNrecIsOff;