Changeset d507c037 in rtems for doc


Ignore:
Timestamp:
04/03/14 17:55:43 (10 years ago)
Author:
Joel Sherrill <joel.sherrill@…>
Branches:
4.11, 5, master
Children:
57740ce8
Parents:
cae120e2
git-author:
Joel Sherrill <joel.sherrill@…> (04/03/14 17:55:43)
git-committer:
Joel Sherrill <joel.sherrill@…> (04/04/14 19:27:27)
Message:

Disable per task variables when SMP is enabled

Per task variables are inherently unsafe in SMP systems. This
patch disables them from the build and adds warnings in the
appropriate documentation and configuration sections.

File:
1 edited

Legend:

Unmodified
Added
Removed
  • doc/user/task.t

    rcae120e2 rd507c037  
    11@c
    2 @c  COPYRIGHT (c) 1988-2008.
     2@c  COPYRIGHT (c) 1988-2014.
    33@c  On-Line Applications Research Corporation (OAR).
    44@c  All rights reserved.
     
    340340A critical point with per-task variables is that each task must separately
    341341request that the same global variable is per-task private.
     342
     343@b{WARNING}: Per-Task variables are inherently broken on SMP systems. They
     344only work correctly when there is one task executing in the system and
     345that task is the logical owner of the value in the per-task variable's
     346location. There is no way for a single memory image to contain the
     347correct value for each task executing on each core. Consequently,
     348per-task variables are disabled in SMP configurations of RTEMS.
    342349
    343350@subsection Building a Task Attribute Set
     
    17801787In this case the destructor function could be `free'.
    17811788
     1789Per-task variables are disabled in SMP configurations and this service
     1790is not available.
     1791
    17821792@page
    17831793
     
    18331843should be considered volatile.
    18341844
     1845Per-task variables are disabled in SMP configurations and this service
     1846is not available.
     1847
    18351848@page
    18361849
     
    18751888@subheading NOTES:
    18761889
    1877 NONE
     1890Per-task variables are disabled in SMP configurations and this service
     1891is not available.
     1892
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