[all-commits] [llvm/llvm-project] 85c276: [Support][Parallel] Initialize threadIndex and add...

[avl-llvm via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 85c2768ce9023ae94d2c70951b3f7e3f33fc2105
      https://github.com/llvm/llvm-project/commit/85c2768ce9023ae94d2c70951b3f7e3f33fc2105
  Author: Alexey Lapshin <a.v.lapshin at mail.ru>
  Date:   2023-05-02 (Tue, 02 May 2023)

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

  Log Message:
  -----------
  [Support][Parallel] Initialize threadIndex and add assertion checking its usage.

That patch adds a check for threadIndex being used with only threads
created by ThreadPoolExecutor. This helps catch two types of errors:

1. If a thread is created not by ThreadPoolExecutor its index may clash
   with the index of another thread. Using threadIndex, in that case, may
   lead to a data race.

2. Index of the main thread(threadIndex == 0) currently clashes with
   the index of thread0 in ThreadPoolExecutor threads. That may lead
   to a data race if main thread and thread0 are executed concurrently.

This patch allows execution tasks on the main thread only in case
parallel::strategy.ThreadsRequested == 1. In all other cases,
assertions check that threadIndex != UINT_MAX(i.e. that task
is executed on a thread created by ThreadPoolExecutor).

Differential Revision: https://reviews.llvm.org/D148916