In uniprocessor and SMP configurations, the context switch extensions
were called during _Thread_Do_dispatch():
void _Thread_Do_dispatch( Per_CPU_Control *cpu_self, ISR_Level level )
{
Thread_Control *executing;
executing = cpu_self->executing;
...
do {
Thread_Control *heir;
heir = _Thread_Get_heir_and_make_it_executing( cpu_self );
...
_User_extensions_Thread_switch( executing, heir );
...
_Context_Switch( &executing->Registers, &heir->Registers );
...
} while ( cpu_self->dispatch_necessary );
...
}
In uniprocessor configurations, this is fine and the context switch
extensions are called for all thread switches except the very first
thread switch to the initialization thread. However, in SMP
configurations, the context switch may be invalidated and updated in the
low-level _Context_Switch() routine. See:
https://docs.rtems.org/branches/master/c-user/symmetric_multiprocessing_services.html#thread-dispatch-details
In case such an update happens, a thread will execute on the processor
which was not seen in the previous call of the context switch
extensions. This can confuse for example event record consumers which
use events generated by a context switch extension.
Fixing this is not straight forward. The context switch extensions call
must move after the low-level context switch. The problem here is that
we may end up in _Thread_Handler(). Adding the context switch
extensions call to _Thread_Handler() covers now also the thread switch
to the initialization thread. We also have to save the last executing
thread (ancestor) of the processor. Registers or the stack cannot be
used for this purpose. We have to add it to the per-processor
information. Existing extensions may be affected, since now context
switch extensions use the stack of the heir thread. The stack checker
is affected by this.
Calling the thread switch extensions in the low-level context switch is
difficult since at this point an intermediate stack is used which is
only large enough to enable servicing of interrupts.
Update #3885.
Move the is SMP enabled configuration constant out of the
configuration table.
Since this was the last configuration constant in
rtems_configuration_table, remove this type.
Update #3875.
With the removal of the CONFIGURE_HAS_OWN_INIT_TASK_TABLE configuration
option at most one Classic API user initialization task can be
configured.
Provide an RTEMS API configuration table for backward compatibility.
Update #3873.
Do not use the rtems_error() function since this function pulls in
exit() and abort(). The abort() function pulls in raise() which pulls
in the whole POSIX signals support. This change saves about 16KiB of
text/rodata on ARM Thumb-2 systems.
Add rtems_scheduler_get_processor_maximum() as a replacement for
rtems_get_processor_count(). The rtems_get_processor_count() is a bit
orphaned. Adopt it by the Scheduler Manager. The count is also
misleading, since the processor set may have gaps and the actual count
of online processors may be less than the value returned by
rtems_get_processor_count().
Update #3732.
Add rtems_scheduler_get_processor() as a replacement for
rtems_get_current_processor(). The rtems_get_current_processor() is a
bit orphaned. Adopt it by the Scheduler Manager. This is in line with
the glibc sched_getcpu() function.
Deprecate rtems_get_current_processor().
Update #3731.
One reason to move the test support into a dedicated library are the
standard output __wrap_*() functions. They may conflict with
application level wrappers.
Update #3199.
The RTEMS_USE_16_BIT_OBJECT define is not set by an RTEMS port. Remove
support for 16-bit object identifiers. If someone really wants to use
RTEMS on a 16-bit target, then it is better to use self-contained
objects instead of playing around with object identifier optimizations.
Update #3603.
Rename
* _Configuration_Interrupt_stack_area_begin in _ISR_Stack_area_begin,
* _Configuration_Interrupt_stack_area_end in _ISR_Stack_area_end, and
* _Configuration_Interrupt_stack_size in _ISR_Stack_size.
Move definitions to <rtems/score/isr.h>. The new names are considerable
shorter and in the right namespace.
Update #3459.
Prepare the interrupt stack which may be used by the boot processor as
initialization stack with the stack sanity pattern. Check the interrupt
stack of the current processor in the thread begin and switch extension.
Update #3459.
LLVM warns about this:
cpukit/libmisc/capture/capture.c:405:30: warning:
taking address of packed member 'time' of class or structure
'rtems_capture_record' may result in an unaligned pointer value
[-Waddress-of-packed-member]
rtems_capture_get_time (&in.time);
And on sparc it generates an unaligned trap which makes smpcapture01
and smpcapture02 test to fail on sparc.
Introduce a new internal define _CONFIGURE_MAXIMUM_PROCESSORS and ensure
that it is _CONFIGURE_MAXIMUM_PROCESSORS > 1 only in SMP configurations.
This avoids to allocate data structures for non-existing additional
processors in uniprocessor configuration.
Update #3459.
