On 21/08/2020 10:40, Richi Dubey wrote:
While trying to debug my code, I realised that the heir set on another
processor does not become that cpu's per_cpu_control->executing after
some time.
On checking the allocate_processor call that set the heir, I saw the
call trace as:
_Scheduler_SMP_Allocate_processor_exact -> _Thread_Dispatch_update_heir :
-------------------------------------
...
} else { (Here this gets executed since the current cpu is different
than the one that gets its executing changed)
_Atomic_Fetch_or_ulong( &cpu_target->message, 0,
ATOMIC_ORDER_RELEASE );
_CPU_SMP_Send_interrupt( _Per_CPU_Get_index( cpu_target ) );
}
............................................
So, how long does it take for heir to become executing on another cpu?
This question is wrt my code at this line
<https://github.com/richidubey/rtems/blob/03d08d02b3e61570f2022845caa44ec6a261f677/cpukit/score/src/schedulerstrongapa.c#L297>.
Is it okay if i use heir here instead of executing (To get the latest
thread intended to be scheduled on the cpu)? Would it mean the same
thing? Is heir==executing when thread_dispatch is set to false?
The thread dispatching uses the per-processor variables executing, heir,
and is_dispatch_necessary. Thread dispatching is always a per-processor
operation. If you want to carry out a thread dispatch on another
processor you have to use an inter-processor interrupt. For the control
flow, see _Thread_Do_dispatch(). Check the variables on the other
processor. After updating the variables you can set a break point to the
inter-processor interrupt handler and check if it is called.
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