core: workaround for Atomic*FieldUpdater bug on some Android devices #3753
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"This is a large but kinda sorta mechanical change..."
This adds a synchronized fallback update mechanism when use of Atomic*FieldUpdater fails. This ignores the use of atomic field updaters in grpclb and round robin load balancer. The bug in the JDK reflection API seems to only be an issue on some Samsung Android 5.0.x devices, but there are enough of these out there that a workaround is necessary.
Question: The try-catch blocks in this PR catch any throwable from initialization of
FieldUpdaterAtomicHelperobjects, logs the throwable, and falls back to the synchronized implementation. Should we only catchNoSuchFieldException? This is the only known exception caused by the bug, so it could/should be ok to specialize the catch blocks. Guava did not do this, however. See prior art: https://github.com/google/guava/blob/fc992745150d95544fec68b9c6e89b5c3bc44b15/guava/src/com/google/common/util/concurrent/AbstractFuture.java#L147