[all-commits] [llvm/llvm-project] 7b25fa: [Support] Attempt to fix deadlock in ThreadGroup

[Alexandre Ganea via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 7b25fa8c7a151e94be46ed8f0a56bf4e2af1c104
      https://github.com/llvm/llvm-project/commit/7b25fa8c7a151e94be46ed8f0a56bf4e2af1c104
  Author: Alexandre Ganea <alexandre.ganea at ubisoft.com>
  Date:   2021-09-18 (Sat, 18 Sep 2021)

  Changed paths:
    M llvm/include/llvm/Support/Parallel.h
    M llvm/lib/Support/Parallel.cpp

  Log Message:
  -----------
  [Support] Attempt to fix deadlock in ThreadGroup

This is an attempt to fix the situation described by https://reviews.llvm.org/D104207#2826290 and PR41508.
See sequence of operations leading to the bug in https://reviews.llvm.org/D104207#3004689

We ensure that the Latch is completely "free" before decrementing the number of TaskGroupInstances.

Differential revision: https://reviews.llvm.org/D109914