RFR: 8267579: Thread::cooked_allocated_bytes() hits assert(left >= right) failed: avoid underflow [v2]

[Markus Grönlund]

> This is a workaround to avoid hitting the assert that was recently added to pointer_delta(). 
> 
> The implementation of cooked_allocated_bytes() is perhaps questionable, in that it reads tlab pointers optimistically. However, the functionality has been in place for a long time, and the impact of changing its behavior more substantially is unknown at this time, hence this defensive workaround to reduce noise and problems seen in general testing.
> 
> Testing: tier1, tier2, tier6, tier8
> 
> Thanks
> Markus

Markus Grönlund has updated the pull request incrementally with one additional commit since the last revision:

  read once

-------------

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/4363/files
  - new: https://git.openjdk.java.net/jdk/pull/4363/files/8e2bc9a0..46eeb2d8

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=4363&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=4363&range=00-01

  Stats: 15 lines in 3 files changed: 13 ins; 0 del; 2 mod
  Patch: https://git.openjdk.java.net/jdk/pull/4363.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/4363/head:pull/4363

PR: https://git.openjdk.java.net/jdk/pull/4363