Message: Don't use sentinel for target
This breaks the check for a barrier (target == null).
Normally we wouldn't care but DeliQueue.nextMessage() can race with remove.
When this happens, we have no way of making a distinction between
a barrier node and a deleted barrier node. Additionally this makes
debugging nextMessage much easier.
Bug: 421623328
Flag: EXEMPT - bugfix
Test: atest CtsOsTestCasesRavenwood:MessageQueueTest#testSyncBarriersWakeup -- --abi x86_64
Change-Id: Ib7497343104b1173acf7942cc16cbe1a7a4dfa02
2 files changed
