tree ac4ef07c7ce33ff0c5912540cd34c5639a47023a
parent 596c58b3dc73a4017d49af6c5037bbd7109fd31e
author Hans Boehm <hboehm@google.com> 1496424566 -0700
committer Hans Boehm <hboehm@google.com> 1496709137 -0700

Document and use AtomicStack concurrency properties

Document the fact that most AtomicStack operations are not atomic,
and document the one case in which they are.

I initially believed, based on its implementation, that PopBackCount
was also intended to be callable concurrently with other PopBackCount
calls. But the SequentiallyConsistent requirement still made
no sense, since there can't safely be any concurrent readers.
On closer inspection, its only client assumes that it has exclusive
access to the stack. Thus this removes the unused, and probably
unusable, thread-safety overhead.

Test: Builds. TreeHugger.

Bug: 62270718
Change-Id: I38e8413fd1851af59a30313f28864496f1d9458b