Prevent fork bombs in ActiveSupport::ForkTracker

[Karazum]

Steps to reproduce

require "active_support/fork_tracker"

def init_for_process
  puts "initializing something for current process"
  ActiveSupport::ForkTracker.after_fork { init_for_process }
end

init_for_process

# ...

Process.fork do 
  puts "os is bombed with endless callbacks"
end

Expected behavior

When running after fork callback, prevent it from being executed in current after_fork_callbacks loop

Actual behavior

after_fork callbacks adds another callback resulting in a endless loop

System configuration

Ruby version: 2.7.6

[byroot]

ActiveSupport::ForkTracker is private API and shouldn't be used by third party code. As such it has no reason to be defensive.