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[Bug malloc/19431] Deadlock between fflush, getdelim, and fork


https://sourceware.org/bugzilla/show_bug.cgi?id=19431

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- Log -----------------------------------------------------------------
https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=29d794863cd6e03115d3670707cc873a9965ba92

commit 29d794863cd6e03115d3670707cc873a9965ba92
Author: Florian Weimer <fweimer@redhat.com>
Date:   Thu Apr 14 09:17:02 2016 +0200

    malloc: Run fork handler as late as possible [BZ #19431]

    Previously, a thread M invoking fork would acquire locks in this order:

      (M1) malloc arena locks (in the registered fork handler)
      (M2) libio list lock

    A thread F invoking flush (NULL) would acquire locks in this order:

      (F1) libio list lock
      (F2) individual _IO_FILE locks

    A thread G running getdelim would use this order:

      (G1) _IO_FILE lock
      (G2) malloc arena lock

    After executing (M1), (F1), (G1), none of the threads can make progress.

    This commit changes the fork lock order to:

      (M'1) libio list lock
      (M'2) malloc arena locks

    It explicitly encodes the lock order in the implementations of fork,
    and does not rely on the registration order, thus avoiding the deadlock.

-----------------------------------------------------------------------

Summary of changes:
 ChangeLog                                          |   24 ++
 malloc/Makefile                                    |    3 +-
 malloc/arena.c                                     |   58 ++----
 .../timer_getoverr.c => malloc/malloc-internal.h   |   30 +--
 malloc/malloc.c                                    |    1 +
 malloc/tst-malloc-fork-deadlock.c                  |  220 ++++++++++++++++++++
 manual/memory.texi                                 |    8 -
 sysdeps/mach/hurd/fork.c                           |   13 ++
 sysdeps/nptl/fork.c                                |   13 +-
 9 files changed, 300 insertions(+), 70 deletions(-)
 copy sysdeps/unix/sysv/linux/timer_getoverr.c => malloc/malloc-internal.h
(57%)
 create mode 100644 malloc/tst-malloc-fork-deadlock.c

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