Notepads where a feature of RTEMS' tasks that simply functioned in
the same way as POSIX keys or threaded local storage (TLS). They were
introduced well before per task variables, which are also deprecated,
and were barely used in favor of their POSIX alternatives.
In addition to their scarce usage, Notepads took up unnecessary memory.
For each task:
- 16 32-bit integers were allocated.
- A total of 64 bytes per task per thread.
This is especially critical in low memory and safety-critical applications.
They are also defined as uint32_t, and therefore are not guaranteed to
hold a pointer.
Lastly, they are not portable solutions for SMP and uniprocessor systems,
like POSIX keys and TLS.
updates #2493.
This mutex implementation uses a thread priority queue with a simple
priority inheritance mechanism (similar to the object based mutexes).
The storage space must be supplied by the user (16 bytes on 32-bit
targets).
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).
A thread join is twofold. There is one thread that exists and an
arbitrary number of threads that wait for the thread exit (one-to-many
relation). The exiting thread may want to wait for a thread that wants
to join its exit (STATES_WAITING_FOR_JOIN_AT_EXIT in
_POSIX_Thread_Exit()). On the other side we need a thread queue for all
the threads that wait for the exit of one particular thread
(STATES_WAITING_FOR_JOIN in pthread_join()).
Update #2035.
Deprecate Classic API Notepads. Mark task_set/get_note() with
the deprecated attribute, and also mark the notepads field.
Replace disable with enable option for notepads in confdefs.h,
and make notepads disabled by default. The previous option
CONFIGURE_DISABLE_CLASSIC_API_NOTEPADS is now unused and
will emit a compile-time warning. A new option
CONFIGURE_ENABLE_CLASSIC_API_NOTEPADS is available to turn
on notepads, but it also will emit a compile-time warning
to indicate that notepads are deprecated.
Closes#2265
CodeSonar flagged this as a case where the user could inject a format
string and cause issues. Since we were not printing anything but a
string, just switching to puts() rather than fprintf(stdout,...) was
sufficient to make this code safer.
CodeSonar flagged this as a case where the user could inject a format
string and cause issues. Since we were not printing anything but a
string, just switching to puts() rather than fprintf(stdout,...) was
sufficient to make this code safer.
snprintf() places a limit on the length of the output from sprintf()
and avoids similar buffer overrun issues.
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.
This simplifies the RTEMS initialization and helps to avoid a memory
overhead. The workspace demands of the IO manager were not included in
the <rtems/confdefs.h> workspace size estimate. This is also fixed as a
side-effect.
Update documentation and move "Specifying Application Defined Device
Driver Table" to the section end. This sub-section is not that
important for the user. Mentioning this at the beginning may lead to
confusion.
The holder field is enough to determine if a mutex is locked or not.
This leads also to better error status codes in case a
rtems_semaphore_release() is done for a mutex without having the
ownership.
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.
Move implementation specific parts of object.h and object.inl into new
header file objectimpl.h. The object.h contains now only the
application visible API.
Move implementation specific parts of states.h and states.inl into new
header file statesimpl.h. The states.h contains now only the
application visible API.
Move implementation specific parts of tasks.h and tasks.inl into new
header file tasksimpl.h. The tasks.h contains now only the application
visible API.
Move implementation specific parts of region.h and region.inl into new
header file regionimpl.h. The region.h contains now only the
application visible API.
Move implementation specific parts of event.h, event.inl, eventset.h and
eventset.inl into new header file eventimpl.h. The event.h contains now
only the application visible API.
Move implementation specific parts of extension.h and extension.inl into
new header file extensionimpl.h. The extension.h contains now only the
application visible API.
Move implementation specific parts of pthread.h and pthread.inl into new
header file pthreadimpl.h. The pthread.h contains now only the
application visible API.
Move implementation specific parts of message.h and message.inl into new
header file messageimpl.h. The message.h contains now only the
application visible API.
The work areas (RTEMS work space and C program heap) will be initialized
now in a separate step and are no longer part of
rtems_initialize_data_structures(). Initialization is performed with
tables of Heap_Area entries. This allows usage of scattered memory
areas present on various small scale micro-controllers.
The sbrk() support API changes also. The bsp_sbrk_init() must now deal
with a minimum size for the first memory chunk to take the configured
work space size into account.
