In case the processor set is not large enough to contain the processor
set owned by the scheduler return RTEMS_INVALID_SIZE instead of
RTEMS_INVALID_NUMBER. This is more in line with other directives since
the issue is related to the size of an object.
Close#4401.
In case the processor set is not large enough to contain the processor
affinity set of the task return RTEMS_INVALID_SIZE instead of
RTEMS_INVALID_NUMBER. This is more in line with other directives since
the issue is related to the size of an object.
Close#4393.
- Remove the printf support leaving the direct printk support configured
with TESTS_USE_PRINTK and all other output goes via a buffered vsniprintf
call to printk.
- Control the test's single init for functions and global data with
TEST_INIT and not CONFIGURE_INIT. They are now separate.
Updates #3170.
No longer unconditionally prevent scheduler changes if the thread owns
resources. Prevent a scheduler change only in case other threads wait
for the resource.
Task priorities are only valid within a scheduler instance. The
rtems_task_set_scheduler() directive moves a task from one scheduler
instance to another using the current priority of the thread. However,
the current task priority of the source scheduler instance is undefined
in the target scheduler instance. Add a third parameter to specify the
priority.
Close#2749.
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.
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.
