Hello,
my next topic is thread restart and delete on SMP. For background information
please have a look at:
http://www.rtems.org/wiki/index.php?title=SMP#Thread_Restart
http://www.rtems.org/wiki/index.php?title=SMP#Thread_Delete
http://www.rtems.org/pipermail/rtems-devel/2013-July/003509.html
http://www.rtems.org/wiki/index.php?title=SMP#Post-Switch_Actions
There are a couple of open PRs in this area:
Priority inheritance mechanism may activate a deleted task
https://www.rtems.org/bugzilla/show_bug.cgi?id=788
SMP race condition between stack free and dispatch
https://www.rtems.org/bugzilla/show_bug.cgi?id=1814
psxcancel reveals NULL pointer access in _Thread_queue_Extract()
https://www.rtems.org/bugzilla/show_bug.cgi?id=2035
Race condition in _Thread_queue_Extract_with_proxy()
https://www.rtems.org/bugzilla/show_bug.cgi?id=2151
Race condition with unified work areas
https://www.rtems.org/bugzilla/show_bug.cgi?id=2152
There are some lock order reversal problems in this area on SMP.
In addition to this the POSIX cleanup handler may be called in the wrong
context (should be called in the context of the deleting thread).
http://pubs.opengroup.org/onlinepubs/009695399/functions/xsh_chap02_09.html
The proposed way to fix the thread restart and delete problems is
1. implement post-switch actions,
2. use post-switch actions to implement Classic and POSIX signals,
3. use post-switch actions to implement thread restart,
4. use post-switch actions to implement thread delete,
5. call thread restart and delete extensions in the context of the restarting
or deleting thread,
6. add ability to disable thread restart and deletion to all threads (not only
POSIX API),
7. disable/enable thread restart and delete in internal mutex obtain/release,
8. protect workspace/heap/objects allocation/free with the allocator mutex (NOT
disabled thread dispatching),
9. add a zombi list of threads for final cleanup (work on demand during thread
create).
It may make sense to add this also to the RTEMS 4.11 release.
--
Sebastian Huber, embedded brains GmbH
Address : Dornierstr. 4, D-82178 Puchheim, Germany
Phone : +49 89 189 47 41-16
Fax : +49 89 189 47 41-09
E-Mail : sebastian.hu...@embedded-brains.de
PGP : Public key available on request.
Diese Nachricht ist keine geschäftliche Mitteilung im Sinne des EHUG.
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