On 21/08/2020 11:12, Richi Dubey wrote:
Is it okay I directly call _Thread_Dispatch_enable while calling
SMP_Preempt (since the latter does not call it) on another processor?
This question is wrt the code at this line
<https://github.com/richidubey/rtems/blob/03d08d02b3e61570f2022845caa44ec6a261f677/cpukit/score/src/schedulerstrongapa.c#L245>.
The thread dispatching works with locks unrelated to the scheduler. It
is all right do do thread dispatching in parallel to the execution of
scheduler code. The scheduler data structures are protected by the
scheduler lock.
This question has comes up because set_affinity does the following in
the order:
_Scheduler_SMP_Preempt_and_schedule_highest_ready
set_affinity
enqueue.
The strong APA's highest_ready preempt a different cpu and allocates a
thread. This CPU can again be preempted while calling the enqueue
corresponding to Strong APA, at which point it would require the
latest scheduled thread on it (the one just assigned it to by
highest_ready if it's the case).
The scheduler code should only use the scheduler internal data
structures. It should define which thread should execute on which
processor. That a thread actually executes on the processor happens
asynchronously to the scheduler operations and is not the business of
the scheduler. This is the job of the thread dispatch code.
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