[SCM] GNU Mach branch, master, updated. v1.7-38-gc78fe96

[Richard Braun]

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- Log -----------------------------------------------------------------
commit c78fe96446794f71a2db7d7e3d43cb15658590a3
Author: Richard Braun <address@hidden>
Date:   Fri Sep 16 04:39:02 2016 +0200

    VM: improve pageout deadlock workaround
    
    Commit 5dd4f67522ad0d49a2cecdb9b109251f546d4dd1 makes VM map entry
    allocation done with VM privilege, so that a VM map isn't held locked
    while physical allocations are paused, which may block the default
    pager during page eviction, causing a system-wide deadlock.
    
    First, it turns out that map entries aren't the only buffers allocated,
    and second, their number can't be easily determined, which makes a
    preallocation strategy very hard to implement.
    
    This change generalizes the strategy of VM privilege increase when a
    VM map is locked.
    
    * device/ds_routines.c (io_done_thread): Use integer values instead
    of booleans when setting VM privilege.
    * kern/thread.c (thread_init, thread_wire): Likewise.
    * vm/vm_pageout.c (vm_pageout): Likewise.
    * kern/thread.h (struct thread): Turn member `vm_privilege' into an
    unsigned integer.
    * vm/vm_map.c (vm_map_lock): New function, where VM privilege is
    temporarily increased.
    (vm_map_unlock): New function, where VM privilege is decreased.
    (_vm_map_entry_create): Remove VM privilege workaround from this
    function.
    * vm/vm_map.h (vm_map_lock, vm_map_unlock): Turn into functions.

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

Summary of changes:
 device/ds_routines.c |    2 +-
 kern/thread.c        |    6 ++---
 kern/thread.h        |    5 ++--
 vm/vm_map.c          |   63 ++++++++++++++++++++++++++++++++------------------
 vm/vm_map.h          |    8 ++-----
 vm/vm_pageout.c      |    2 +-
 6 files changed, 49 insertions(+), 37 deletions(-)


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