[all-commits] [llvm/llvm-project] c82f3c: [scudo] Add StackDepot lock to enable/disable. (#7...

[Evgenii Stepanov via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: c82f3caf5683a443692162d9fbebc31019af7ce8
      https://github.com/llvm/llvm-project/commit/c82f3caf5683a443692162d9fbebc31019af7ce8
  Author: Evgenii Stepanov <eugeni.stepanov at gmail.com>
  Date:   2024-01-29 (Mon, 29 Jan 2024)

  Changed paths:
    M compiler-rt/lib/scudo/standalone/combined.h
    M compiler-rt/lib/scudo/standalone/stack_depot.h

  Log Message:
  -----------
  [scudo] Add StackDepot lock to enable/disable. (#79670)

Scudo grabs all allocator locks in a pthread_atfork before the fork, and releases them after. This allows malloc to be used in a fork child of a multithreaded process, which is expressly forbidden by the standard, but very widely used. For example, Android's init uses std::string after fork when spawning services in android::init::EnterNamespaces and other places.

Any lock that is necessary to serve an allocator call must be handled this way. Otherwise there is a possibility that the lock is held during the call to fork, which results in it being held forever in the child process, and the next operation that needs it deadlocks.