[RTEMS Project] #2752: Relax execution enviroment for thread begin extensions

[RTEMS trac]

#2752: Relax execution enviroment for thread begin extensions
-----------------------------+-----------------------------
 Reporter:  sebastian.huber  |      Owner:  sebastian.huber
     Type:  enhancement      |     Status:  new
 Priority:  normal           |  Milestone:  4.12
Component:  cpukit           |    Version:  4.10
 Severity:  normal           |   Keywords:
-----------------------------+-----------------------------
 Currently, the thread begin extensions are invoked with thread dispatching
 disabled.  There is an explanation for this in the code

 {{{
   /*
    * Take care that 'begin' extensions get to complete before
    * 'switch' extensions can run.  This means must keep dispatch
    * disabled until all 'begin' extensions complete.
    */
   _User_extensions_Thread_begin( executing );
 }}}

 However, the switch extension is always invoked before the thread begin
 extension for all threads except the initialization thread.  A thread
 dispatch disabled contexts drastically limits the work which can be
 carried out in the thread begin extensions.  It is for example not
 possible to call malloc(), create POSIX keys or access C++ thread local
 storage.

 The thread begin extension should execute in a normal thread context.
 Thread begin extensions that are disturbed by a thread dispatch should
 deal with this locally.

 With the availability of C++ thread local storage in RTEMS being able to
 pre-initialize such objects in the thread begin extension would be quite
 handy.

--
Ticket URL: <http://devel.rtems.org/ticket/2752>
RTEMS Project <http://www.rtems.org/>
RTEMS Project