639353 - hang during keyboard input

Status: RESOLVED FIXED

(Core Graveyard :: Widget: Android, defect)

Description

[Dave Miller [:justdave]]

Mozilla/5.0 (Android; Linux armv7l; rv:2.0b13pre) Gecko/20110306 Firefox/4.0b13pre Fennec/4.0b6pre

HTC Evo 4G, Android 2.2

Went to https://rcam.target.com/ and started typing my username.

My username is 10 letters, after typing the 9th letter, Fennec completely froze up, and the OS offered to force quit.  Repeated this 3 times, then went on IRC and mentioned it, then tried again and it worked the 4th time without hanging.

blassey said this was a conceivable regression from a recent commit involving syncing state between java and C and I ought to file it anyway.

Comment 1

[Brad Lassey [:blassey] (use needinfo?)]

I also hit this while editing this bug

Comment 2

[Brad Lassey [:blassey] (use needinfo?)]

Attachment: patch

this is my theory of what's going on:

480     private static final ReentrantLock mGeckoSyncLock = new ReentrantLock();
481     private static final Condition     mGeckoSyncCond = mGeckoSyncLock.newCondition();
482     private static boolean mGeckoSyncAcked;
483 
484     // Block the current thread until the Gecko event loop is caught up
485     public static void geckoEventSync() {
486         GeckoAppShell.sendEventToGecko(
487             new GeckoEvent(GeckoEvent.GECKO_EVENT_SYNC));
<----------------------------------- context switch, acknowledgeEventSync() runs, mGeckoSyncAcked is true
488         mGeckoSyncLock.lock();
489         mGeckoSyncAcked = false;
490         while (!mGeckoSyncAcked) {
491             try {
492               mGeckoSyncCond.await();   <-------- we wait here, but since acknowledgeEventSync() already ran we won't get singnaled
493             } catch (InterruptedException e) {
494               break;
495             }
496         }
497         mGeckoSyncLock.unlock();
498     }
499 
500     // Signal the Java thread that it's time to wake up
501     public static void acknowledgeEventSync() {
502         mGeckoSyncLock.lock();
503         mGeckoSyncAcked = true;
504         try {
505             mGeckoSyncCond.signal();
506         } finally {
507             mGeckoSyncLock.unlock();
508         }
509     }

Comment 3

[Brad Lassey [:blassey] (use needinfo?)]

pushed http://hg.mozilla.org/mozilla-central/rev/1240004b90e6

Comment 4

[Doug Turner (:dougt)]

This is a really scary change - holding a lock while calling sendEventToGecko probably isn't the best thing.

can we instead use a tristate value for mGeckoSyncAcked?

Comment 5

[Brad Lassey [:blassey] (use needinfo?)]

Attachment: patch to use countdownlatch

Comment 6

[Brad Lassey [:blassey] (use needinfo?)]

pushed http://hg.mozilla.org/mozilla-central/rev/86a09f53b7ee