Ensure that the global construction is performed in the context of the
first initialization thread. On SMP this was not guaranteed in the
previous implementation.
Do not use sprintf() in thread dispatch critical sections to avoid
corruption of profiling samples. Update test to reflect thread the life
cycle changes.
This avoids test durations of more than one hour on fast targets, since
fast targets can count a lot during one clock tick period, so the minor
loop iteration count was quite high. Estimate now the test body
duration to iterate only through the interesting time window.
Add and use interrupt_critical_section_test().
Simplify _RBTree_Insert() and _RBTree_Extract(). Remove more
superfluous NULL pointer checks. Change _RBTree_Is_root() to use only
the node. Add parent parameter to _RBTree_Sibling(). Delete
_RBTree_Grandparent() and _RBTree_Parent_sibling().
Only use the parent pointer, since this pointer is never NULL for nodes
which are part of a tree.
Rename functions from *_off_rbtree() to *_off_tree().
Remove compare function and is unique indicator from the control
structure. Rename RBTree_Compare_function to RBTree_Compare. Rename
rtems_rbtree_compare_function to rtems_rbtree_compare. Provide C++
compatible initializers. Add compare function and is unique indicator
to _RBTree_Find(), _RBTree_Insert(), rtems_rbtree_find() and
rtems_rbtree_insert(). Remove _RBTree_Is_unique() and
rtems_rbtree_is_unique(). Remove compare function and is unique
indicator from _RBTree_Initialize_empty() and
rtems_rbtree_initialize_empty().
A resource is something that has at most one owner at a time and may
have multiple rivals in case an owner is present. The owner and rivals
are impersonated via resource nodes. A resource is represented via the
resource control structure. The resource controls and nodes are
organized as trees. It is possible to detect deadlocks via such a
resource tree. The _Resource_Iterate() function can be used to iterate
through such a resource tree starting at a top node.
Add basic support for the Multiprocessor Resource Sharing Protocol
(MrsP).
The Multiprocessor Resource Sharing Protocol (MrsP) is defined in A.
Burns and A.J. Wellings, A Schedulability Compatible Multiprocessor
Resource Sharing Protocol - MrsP, Proceedings of the 25th Euromicro
Conference on Real-Time Systems (ECRTS 2013), July 2013. It is a
generalization of the Priority Ceiling Protocol to SMP systems. Each
MrsP semaphore uses a ceiling priority per scheduler instance. These
ceiling priorities can be specified with rtems_semaphore_set_priority().
A task obtaining or owning a MrsP semaphore will execute with the
ceiling priority for its scheduler instance as specified by the MrsP
semaphore object. Tasks waiting to get ownership of a MrsP semaphore
will not relinquish the processor voluntarily. In case the owner of a
MrsP semaphore gets preempted it can ask all tasks waiting for this
semaphore to help out and temporarily borrow the right to execute on one
of their assigned processors.
The help out feature is not implemented with this patch.
Avoid using newlib's gmtime_r call which fails with a max signed int.
Add an RTEMS specific version for 1/1/1988 to 31/12/2100.
Update sp2038 to test every day from 1/1/1988 to 31/12/2100. Only days
need be tested as the code splits the seconds based on days.
Enable usage of _Thread_Set_life_protection() in thread dispatch
critical sections. This can be used to enable the thread
life-protection with thread dispatching disabled and then enable thread
dispatching.
The function to change a thread priority was too complex. Simplify it
with a new scheduler operation. This increases the average case
performance due to the simplified logic. The interrupt disabled
critical section is a bit prolonged since now the extract, update and
enqueue steps are executed atomically. This should however not impact
the worst-case interrupt latency since at least for the Deterministic
Priority Scheduler this sequence can be carried out with a wee bit of
instructions and no loops.
Add _Scheduler_Change_priority() to replace the sequence of
- _Thread_Set_transient(),
- _Scheduler_Extract(),
- _Scheduler_Enqueue(), and
- _Scheduler_Enqueue_first().
Delete STATES_TRANSIENT, _States_Is_transient() and
_Thread_Set_transient() since this state is now superfluous.
With this change it is possible to get rid of the
SCHEDULER_SMP_NODE_IN_THE_AIR state. This considerably simplifies the
implementation of the new SMP locking protocols.
Rename scheduler per-thread information into scheduler nodes using
Scheduler_Node as the base type. Use inheritance for specialized
schedulers.
Move the scheduler specific states from the thread control block into
the scheduler node structure.
Validate the SMP scheduler node state transitions in case RTEMS_DEBUG is
defined.
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.
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.
Provide a file per BSP to list tests that do not build for a BSP. This change
removes the BSP_SMALL_MEMORY hack from the code. That hack was a
mistake.
Provide configuration files for each BSP with tests that cannot build.
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.
