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NuttX TODO List (Last updated April 15, 2017)
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This file summarizes known NuttX bugs, limitations, inconsistencies with
standards, things that could be improved, and ideas for enhancements. This
TODO list does not include issues associated with individual boar ports. See
also the individual README.txt files in the configs/ sub-directories for
issues related to each board port.
Gregory Nutt
committed
(1) SMP
(0) Power Management (drivers/pm)
(3) Signals (sched/signal, arch/)
(3) pthreads (sched/pthread)
Gregory Nutt
committed
(0) Message Queues (sched/mqueue)
(8) Kernel/Protected Build
(6) Binary loaders (binfmt/)
Gregory Nutt
committed
(4) USB (drivers/usbdev, drivers/usbhost)
(10) File system/Generic drivers (fs/, drivers/)
(2) Network Utilities (apps/netutils/)
(1) NuttShell (NSH) (apps/nshlib)
(1) System libraries apps/system (apps/system)
Title: CHILD PTHREAD TERMINATION
Description: When a tasks exits, shouldn't all of its child pthreads also be
terminated?
Status: Closed. No, this behavior will not be implemented.
Priority: Medium, required for good emulation of process/pthread model.
Description: In the POSIX description of this function the pause() function
must suspend the calling thread until delivery of a signal whose
action is either to execute a signal-catching function or to
terminate the process. The current implementation only waits for
any non-blocked signal to be received. It should only wake up if
the signal is delivered to a handler.
Status: Open.
Priority: Medium Low.
Title: ON-DEMAND PAGING INCOMPLETE
Description: On-demand paging has recently been incorporated into the RTOS.
The design of this feature is described here:
http://www.nuttx.org/NuttXDemandPaging.html.
As of this writing, the basic feature implementation is
complete and much of the logic has been verified. The test
harness for the feature exists only for the NXP LPC3131 (see
configs/ea3131/pgnsh and locked directories). There are
some limitations of this testing so I still cannot say that
the feature is fully functional.
Status: Open. This has been put on the shelf for some time.
Description: get_environ_ptr() (sched/sched_getenvironptr.c) is not implemented.
The representation of the environment strings selected for
NuttX is not compatible with the operation. Some significant
re-design would be required to implement this function and that
Description: timer_getoverrun() (sched/timer_getoverrun.c) is not implemented.
Status: Open
Priority: Low -- There is no plan to implement this.
Description: Simplified 'execl()' and 'execv()' functions are provided by
NuttX. NuttX does not support processes and hence the concept
of overlaying a tasks process image with a new process image
does not make any sense. In NuttX, these functions are
wrapper functions that:
1. Call the non-standard binfmt function 'exec', and then
2. exit(0).
As a result, the current implementations of 'execl()' and
'execv()' suffer from some incompatibilities, the most
serious of these is that the exec'ed task will not have
the same task ID as the vfork'ed function. So the parent
function cannot know the ID of the exec'ed task.
Status: Open
Priority: Medium Low for now
Title: ISSUES WITH atexit(), on_exit(), AND pthread_cleanup_pop()
patacongo
committed
Description: These functions execute with the following bad properties:
patacongo
committed
1. They run with interrupts disabled,
2. They run in supervisor mode (if applicable), and
3. They do not obey any setup of PIC or address
environments. Do they need to?
4. In the case of task_delete() and pthread_cancel() without
defferred cancellation, these callbacks will run on the
thread of execution and address context of the caller of
task_delete() or pthread_cancel(). That is very bad!
patacongo
committed
The fix for all of these issues it to have the callbacks
signal handlers. Signals are delivered differently in
PROTECTED and KERNEL modes: The deliver is involes a
signal handling trampoline function in the user address
space and two signal handlers: One to call the signal
handler trampoline in user mode (SYS_signal_handler) and
on in with the signal handler trampoline to return to
supervisor mode (SYS_signal_handler_return)
The primary difference is in the location of the signal
handling trampoline:
- In PROTECTED mode, there is on a single user space blob
with a header at the beginning of the block (at a well-
known location. There is a pointer to the signal handler
trampoline function in that header.
- In the KERNEL mode, a special process signal handler
trampoline is used at a well-known location in every
process address space (ARCH_DATA_RESERVE->ar_sigtramp).
patacongo
committed
Status: Open
Priority: Medium Low. This is an important change to some less
important interfaces. For the average user, these
functions are just fine the way they are.
Title: execv() AND vfork()
Description: There is a problem when vfork() calls execv() (or execl()) to
start a new application: When the parent thread calls vfork()
it receives and gets the pid of the vforked task, and *not*
the pid of the desired execv'ed application.
The same tasking arrangement is used by the standard function
posix_spawn(). However, posix_spawn uses the non-standard, internal
NuttX interface task_reparent() to replace the child's parent task
with the caller of posix_spawn(). That cannot be done with vfork()
because we don't know what vfork() is going to do.
Any solution to this is either very difficult or impossible without
an MMU.
Status: Open
Priority: Low (it might as well be low since it isn't going to be fixed).
patacongo
committed
Title: errno IS NOT SHARED AMONG THREADS
Description: In NuttX, the errno value is unique for each thread. But for
bug-for-bug compatibility, the same errno should be shared by
the task and each thread that it creates. It is *very* easy
to make this change: Just move the pterrno field from
struct tcb_s to struct task_group_s. However, I am still not
sure if this should be done or not.
Status: Closed. The existing solution is better (although its
incompatibilities could show up in porting some code).
patacongo
committed
Priority: Low
Title: SCALABILITY
Description: Task control information is retained in simple lists. This
is completely appropriate for small embedded systems where
the number of tasks, N, is relatively small. Most list
operations are O(N). This could become an issue if N gets
very large.
In that case, these simple lists should be replaced with
something more performant such as a balanced tree in the
case of ordered lists. Fortunately, most internal lists are
hidden behind simple accessor functions and so the internal
data structures can be changed if need with very little impact.
Explicitly reference to the list structure are hidden behind
Gregory Nutt
committed
the macro this_task().
Status: Open
Priority: Low. Things are just the way that we want them for the way
that NuttX is used today.
Title: INTERNAL VERSIONS OF USER FUNCTIONS
Description: The internal NuttX logic uses the same interfaces as does
the application. That sometime produces a problem because
there is "overloaded" functionality in those user interfaces
that are not desireable.
For example, having cancellation points hidden inside of the
OS can cause non-cancellation point interfaces to behave
strangely. There was a change recently in pthread_cond_wait()
and pthread_cond_timedwait() recently to effectively disable
the cancellation point behavior of sem_init(). This was
accomplished with two functions: pthread_disable_cancel()
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