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Commit 0060bd42 authored by Jeff Sharkey's avatar Jeff Sharkey
Browse files

BroadcastQueue: limit runnable to avoid starvation. 

When a process has a large number of pending broadcasts, they could
end up starving other runnable processes.  This change retires a
running queue if we've made reasonable progress and someone else is
waiting.

Bug: 245771249
Test: atest FrameworksMockingServicesTests:BroadcastQueueTest
Change-Id: Ie60625d8fba577ccf1cb8d1cee212fffabb68ef7
parent 527e10cc

services/core/java/com/android/server/am/BroadcastProcessQueue.java

+19 −0
Original line number Diff line number Diff line
@@ -95,6 +95,15 @@ class BroadcastProcessQueue { 
     */

    private int mActiveIndex;



    /**

     * Count of {@link #mActive} broadcasts that have been dispatched since this

     * queue was last idle.

     */

    private int mActiveCountSinceIdle;



    /**

     * Count of {@link #mPending} broadcasts of these various flavors.

     */

    private int mCountForeground;

    private int mCountOrdered;

    private int mCountAlarm;
@@ -170,6 +179,14 @@ class BroadcastProcessQueue { 
        }

    }



    /**

     * Count of {@link #mActive} broadcasts that have been dispatched since this

     * queue was last idle.

     */

    public int getActiveCountSinceIdle() {

        return mActiveCountSinceIdle;

    }



    /**

     * Set the currently active broadcast to the next pending broadcast.

     */
@@ -179,6 +196,7 @@ class BroadcastProcessQueue { 
        final SomeArgs next = mPending.removeFirst();

        mActive = (BroadcastRecord) next.arg1;

        mActiveIndex = next.argi1;

        mActiveCountSinceIdle++;

        next.recycle();

        if (mActive.isForeground()) {

            mCountForeground--;
@@ -198,6 +216,7 @@ class BroadcastProcessQueue { 
    public void makeActiveIdle() {

        mActive = null;

        mActiveIndex = 0;

        mActiveCountSinceIdle = 0;

    }



    public void setActiveDeliveryState(int deliveryState) {

services/core/java/com/android/server/am/BroadcastQueueModernImpl.java

+14 −2
Original line number Diff line number Diff line
@@ -101,6 +101,14 @@ class BroadcastQueueModernImpl extends BroadcastQueue { 
    // TODO: shift hard-coded defaults to BroadcastConstants

    private static final int MAX_RUNNING_PROCESS_QUEUES = 4;



    /**

     * Maximum number of active broadcasts to dispatch to a "running" process

     * queue before we retire them back to being "runnable" to give other

     * processes a chance to run.

     */

    // TODO: shift hard-coded defaults to BroadcastConstants

    private static final int MAX_RUNNING_ACTIVE_BROADCASTS = 16;



    /**

     * Map from UID to per-process broadcast queues. If a UID hosts more than

     * one process, each additional process is stored as a linked list using
@@ -475,10 +483,14 @@ class BroadcastQueueModernImpl extends BroadcastQueue { 
        queue.setActiveDeliveryState(deliveryState);



        // TODO: cancel any outstanding ANR timeout

        // TODO: limit number of broadcasts in a row to avoid starvation

        // TODO: if we're the last receiver of this broadcast, record to history



        if (queue.isRunnable() && queue.isProcessWarm()) {

        // Even if we have more broadcasts, if we've made reasonable progress

        // and someone else is waiting, retire ourselves to avoid starvation

        final boolean shouldRetire = (mRunnableHead != null)

                && (queue.getActiveCountSinceIdle() > MAX_RUNNING_ACTIVE_BROADCASTS);



        if (queue.isRunnable() && queue.isProcessWarm() && !shouldRetire) {

            // We're on a roll; move onto the next broadcast for this process

            queue.makeActiveNextPending();

            scheduleReceiverWarmLocked(queue);