[Bug malloc/19182] malloc deadlock between ptmalloc_lock_all and _int_new_arena

[cvs-commit at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=19182

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https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=90c400bd4904b0240a148f0b357a5cbc36179239

commit 90c400bd4904b0240a148f0b357a5cbc36179239
Author: Florian Weimer <fweimer@redhat.com>
Date:   Mon Dec 21 16:42:46 2015 +0100

    malloc: Fix list_lock/arena lock deadlock [BZ #19182]

        * malloc/arena.c (list_lock): Document lock ordering requirements.
        (free_list_lock): New lock.
        (ptmalloc_lock_all): Comment on free_list_lock.
        (ptmalloc_unlock_all2): Reinitialize free_list_lock.
        (detach_arena): Update comment.  free_list_lock is now needed.
        (_int_new_arena): Use free_list_lock around detach_arena call.
        Acquire arena lock after list_lock.  Add comment, including FIXME
        about incorrect synchronization.
        (get_free_list): Switch to free_list_lock.
        (reused_arena): Acquire free_list_lock around detach_arena call
        and attached threads counter update.  Add two FIXMEs about
        incorrect synchronization.
        (arena_thread_freeres): Switch to free_list_lock.
        * malloc/malloc.c (struct malloc_state): Update comments to
        mention free_list_lock.

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

Summary of changes:
 ChangeLog       |   19 +++++++++++++++
 malloc/arena.c  |   66 ++++++++++++++++++++++++++++++++++++++++++------------
 malloc/malloc.c |    6 ++--
 3 files changed, 73 insertions(+), 18 deletions(-)

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