[ruby-cvs:60536] normal:r53373 (trunk): thread_pthread.c (rb_thread_create_timer_thread): fix race

normal at ruby-lang.org normal at ruby-lang.org
Wed Dec 30 03:20:28 JST 2015

normal	2015-12-30 03:20:27 +0900 (Wed, 30 Dec 2015)

  New Revision: 53373


    thread_pthread.c (rb_thread_create_timer_thread): fix race
    This fixes an occasional [ASYNC BUG] failure in
    bootstraptest/test_fork.rb '[ruby-dev:37934]'
    which tests fork/pthread_create failure by setting
    RLIMIT_NPROC to 1 and triggering EAGAIN on pthread_create
    when attempting to recreate the timer thread.
    The problem timeline is as follows:
    thread 1                           thread 2
    pthread_create fails               pipe looks valid, write!
    CLOSE_INVALIDATE (x4)              EBADF -> ASYNC BUG
    The checks in rb_thread_wakeup_timer_thread_low only tried to
    guarantee proper ordering with native_stop_timer_thread, not
    rb_thread_create_timer_thread :x
    Now, this should allow rb_thread_create_timer_thread to
    synchronize properly with rb_thread_wakeup_timer_thread_low by
    delaying the validation marking of the timer_thread_pipe until
    we are certain the timer thread is alive.
    In this version, rb_thread_wakeup_timer_thread_low becomes a
    noop.  Threading is still completely broken with NPROC==1, but
    there's not much we can do about it beside warn the user.
    We no longer spew a scary [ASYNC BUG] message or dump core
    on them.
    * thread_pthread.c (setup_communication_pipe): delay setting owner
      (rb_thread_create_timer_thread): until thread creation succeeds
      [ruby-core:72590] [Bug #11922]

  Modified files:

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