| Commit message (Collapse) | Author | Age | Files | Lines |
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Move _Scheduler_Get() and _Scheduler_Set() out of the #if
defined(__RTEMS_HAVE_SYS_CPUSET_H__) block.
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Do not cover the includes with an extern "C".
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We must not alter the is executing indicator in
_CPU_Context_Initialize() since this would cause an invalid state during
a self restart.
The is executing indicator must be valid at creation time since
otherwise _Thread_Kill_zombies() uses an undefined value for not started
threads. This could result in a system life lock.
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Virtual machines with paravirtualization exist not only on x86.
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Initialize the ISR lock only once and destroy it properly.
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The current implementation of task migration in RTEMS has some
implications with respect to the interrupt latency. It is crucial to
preserve the system invariant that a task can execute on at most one
processor in the system at a time. This is accomplished with a boolean
indicator in the task context. The processor architecture specific
low-level task context switch code will mark that a task context is no
longer executing and waits that the heir context stopped execution
before it restores the heir context and resumes execution of the heir
task. So there is one point in time in which a processor is without a
task. This is essential to avoid cyclic dependencies in case multiple
tasks migrate at once. Otherwise some supervising entity is necessary to
prevent life-locks. Such a global supervisor would lead to scalability
problems so this approach is not used. Currently the thread dispatch is
performed with interrupts disabled. So in case the heir task is
currently executing on another processor then this prolongs the time of
disabled interrupts since one processor has to wait for another
processor to make progress.
It is difficult to avoid this issue with the interrupt latency since
interrupts normally store the context of the interrupted task on its
stack. In case a task is marked as not executing we must not use its
task stack to store such an interrupt context. We cannot use the heir
stack before it stopped execution on another processor. So if we enable
interrupts during this transition we have to provide an alternative task
independent stack for this time frame. This issue needs further
investigation.
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A default handler is not necessary. The test message sender must ensure
that a handler is installed.
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Always initialize the freechain. This prevents a NULL pointer access in
case no initial key value pairs are defined.
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This handler can be used to test the inter-processor interrupt
implementation.
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Avoid the SMP_FATAL_SCHEDULER_WITHOUT_PROCESSORS fatal error and make it
a run-time error in rtems_scheduler_ident() and _Scheduler_Get_by_id().
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Use register g6 for the per-CPU control of the current processor. The
register g6 is reserved for the operating system by the SPARC ABI. On
Linux register g6 is used for a similar purpose with the same method
since 1996.
The register g6 must be initialized during system startup and then must
remain unchanged.
Since the per-CPU control is used in all critical sections of the
operating system, this is a performance optimization for the operating
system core procedures. An additional benefit is that the low-level
context switch and interrupt processing code is now identical on non-SMP
and SMP configurations.
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The registers g2 through g4 are reserved for applications. GCC uses
them as volatile registers by default. So they are treated like
volatile registers in RTEMS as well.
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Add optional method _CPU_Get_current_per_CPU_control() to obtain the
per-CPU control of the current processor.
This is optional. Not every CPU port needs this. It is only an
optional optimization variant. In case this macro is undefined, the
default implementation using the current processor index will be used.
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Added define for CONFIGURE_SEMAPHORES_FOR_NFS when networking disabled.
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Add support to account for the semaphores used by the file systems.
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Use "cpu" for an arbitrary Per_CPU_Control variable.
Use "cpu_self" for the Per_CPU_Control of the current processor.
Use "cpu_index" for an arbitrary processor index.
Use "cpu_index_self" for the processor index of the current processor.
Use "cpu_count" for the processor count obtained via
_SMP_Get_processor_count().
Use "cpu_max" for the processor maximum obtained by
rtems_configuration_get_maximum_processors().
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These values are already zero initialized by C run-time setup.
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POSIX keys and key value pairs support now the unlimited option.
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The _Scheduler_SMP_Allocate_processor() and _Thread_Dispatch() exchange
information without locks. Make sure we use the right load/store
ordering.
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Clustered/partitioned scheduling helps to control the worst-case
latencies in the system. The goal is to reduce the amount of shared
state in the system and thus prevention of lock contention. Modern
multi-processor systems tend to have several layers of data and
instruction caches. With clustered/partitioned scheduling it is
possible to honour the cache topology of a system and thus avoid
expensive cache synchronization traffic.
We have clustered scheduling in case the set of processors of a system
is partitioned into non-empty pairwise-disjoint subsets. These subsets
are called clusters. Clusters with a cardinality of one are partitions.
Each cluster is owned by exactly one scheduler instance.
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Make rtems_task_get_affinity() and rtems_task_set_affinity() available
on non-SMP configurations. Allow larger CPU sets.
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The thread control block contains fields that point to application
configuration dependent memory areas, like the scheduler information,
the API control blocks, the user extension context table, the RTEMS
notepads and the Newlib re-entrancy support. Account for these areas in
the configuration and avoid extra workspace allocations for these areas.
This helps also to avoid heap fragementation and reduces the per thread
memory due to a reduced heap allocation overhead.
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