Move the storage for the thread queue heads to the threads. Each thread
provides a set of thread queue heads allocated from a dedicated memory
pool. In case a thread blocks on a queue, then it lends its heads to
the queue. In case the thread unblocks, then it takes a free set of
threads from the queue. Since a thread can block on at most one queue
this works. This mechanism is used in FreeBSD. The motivation for this
change is to reduce the memory demands of the synchronization objects.
On a 32-bit uni-processor configuration the Thread_queue_Control size is
now 8 bytes, compared to 64 bytes in RTEMS 4.10 (other changes reduced
the size as well).
Avoid Thread_Control typedef in <rtems/score/percpu.h>. This helps to
get rid of the <rtems/score/percpu.h> include in <rtems/score/thread.h>
which exposes a lot of implementation details.
Aggregate several critical sections into a bigger one. Sending and
receiving messages is now protected by an ISR lock. Thread dispatching
is only disabled in case a blocking operation is necessary. The message
copy procedure is done inside the critical section (interrupts
disabled). Thus this change may have a negative impact on the interrupt
latency in case very large messages are transferred.
Update #2273.
Move the complete thread queue enqueue procedure into
_Thread_queue_Enqueue_critical(). It is possible to use the thread
queue lock to protect state of the object embedding the thread queue.
This enables per object fine grained locking in the future.
Delete _Thread_queue_Enter_critical_section().
Update #2273.
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().
The thread deletion is now supported on SMP.
This change fixes the following PRs:
PR1814: SMP race condition between stack free and dispatch
PR2035: psxcancel reveals NULL pointer access in _Thread_queue_Extract()
The POSIX cleanup handler are now called in the right context (should be
called in the context of the terminating thread).
http://pubs.opengroup.org/onlinepubs/009695399/functions/xsh_chap02_09.html
Add a user extension the reflects a thread termination event. This is
used to reclaim the Newlib reentrancy structure (may use file
operations), the POSIX cleanup handlers and the POSIX key destructors.
Add a local context structure to the SMP lock API for acquire and
release pairs. This context can be used to store the ISR level and
profiling information. It may be later used to enable more
sophisticated lock algorithms, e.g. MCS locks.
There is only one lock that cannot be used with a local context. This
is the per-CPU lock since here we would have to transfer the local
context through a context switch which is very complicated.
Formerly POSIX keys were only enabled when POSIX threads
were enabled. Because they are a truly safe alternative
to per-task variables in an SMP system, they are being
enabled in all configurations.
Provide support for latest Newlib <pthread.h> change. The cleanup
contexts are stored on the thread stack. This is conformant with the
POSIX requirements for the pthread_cleanup_push() and
pthread_cleanup_pop() statement pair.
Passing an invalid pointer as the routine to pthread_cleanup_push() is
now a usage error and the behaviour is undefined.
Add and use _POSIX_signals_Release(). The post-switch handler is not
protected by disabled thread dispatching. Use proper SMP lock for
signal management.
Change pthread_once from using disabled pre-emption to using a
pthread mutex making it SMP safe. GCC using a posix threading
model uses pthread_once.
The pthread mutex requires at least 1 mutex is configured so
confdefs.h has been updated to account for the internal
mutex.
Use the POSIX configuration value directly. Use right type early and
avoid casts. Use proper unlimited objects API. Check workspace
allocation. Make functions static.
