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Commit 8f02e2d6 authored by Phil Burk's avatar Phil Burk Committed by Glenn Kasten
Browse files

aaudio: fix race condition in timestamp path 

There was a potential race between setting the first timestamp
and reading the first timestamp that could cause the timestamp service
thread to exit. This would cause the client to not get any timestamps.
Then the timing model would not advance and the stream would stall.
This could result in read() or write() returning zero,
or a TIMEOUT error.

This was rare except for some devices that had different
timing in the HAL.

Bug: 68271891
Bug: 117557847
Test: adb shell write_sine_callback -pl -m2 -n2 -s2 -c2 -l100
Test: atest CtsNativeMediaAAudioTestCases
Change-Id: Ib0974a576aaa17ff8de40899e60ed56015027bd7
parent efd99ec8

services/oboeservice/AAudioServiceEndpoint.h

+7 −0
Original line number Diff line number Diff line
@@ -77,6 +77,13 @@ public: 
     */

    virtual aaudio_result_t getFreeRunningPosition(int64_t *positionFrames, int64_t *timeNanos) = 0;



    /**

     * Set time that the associated frame was presented to the hardware.

     *

     * @param positionFrames receive position, input value is ignored

     * @param timeNanos receive time, input value is ignored

     * @return AAUDIO_OK or AAUDIO_ERROR_UNAVAILABLE or other negative error

     */

    virtual aaudio_result_t getTimestamp(int64_t *positionFrames, int64_t *timeNanos) = 0;



    int32_t getFramesPerBurst() const {

services/oboeservice/AAudioServiceEndpointShared.cpp

+9 −1
Original line number Diff line number Diff line
@@ -192,5 +192,13 @@ aaudio_result_t AAudioServiceEndpointShared::getFreeRunningPosition(int64_t *pos 


aaudio_result_t AAudioServiceEndpointShared::getTimestamp(int64_t *positionFrames,

                                                          int64_t *timeNanos) {

    return mStreamInternal->getTimestamp(CLOCK_MONOTONIC, positionFrames, timeNanos);

    aaudio_result_t result = mStreamInternal->getTimestamp(CLOCK_MONOTONIC, positionFrames, timeNanos);

    if (result == AAUDIO_ERROR_INVALID_STATE) {

        // getTimestamp() can return AAUDIO_ERROR_INVALID_STATE if the stream has

        // not completely started. This can cause a race condition that kills the

        // timestamp service thread.  So we reduce the error to a less serious one

        // that allows the timestamp thread to continue.

        result = AAUDIO_ERROR_UNAVAILABLE;

    }

    return result;

}