Newer
Older
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
This file summarizes known NuttX bugs, limitations, inconsistencies with
standards, things that could be improved, and ideas for enhancements. See
also individual README.txt files in the configs/ sub-directories for each
board port.
(3) Signals (sched/, arch/)
patacongo
committed
(2) pthreads (sched/)
Gregory Nutt
committed
(4) C++ Support
(6) Binary loaders (binfmt/)
Gregory Nutt
committed
(4) USB (drivers/usbdev, drivers/usbhost)
(10) Libraries (libc/, )
(11) File system/Generic drivers (fs/, drivers/)
(2) Build system / Toolchains
(2) ARM/i.MX (arch/arm/src/imx/)
(7) ARM/LPC214x (arch/arm/src/lpc214x/)
(0) ARM/LPC43x (arch/arm/src/lpc43xx/)
(2) ARM/STR71x (arch/arm/src/str71x/)
(2) ARM/LM3S6918 (arch/arm/src/tiva/)
Gregory Nutt
committed
(x) ARM/SAMA5D3 ((arch/arm/src/sama5/)
(5) ARM/STM32 (arch/arm/src/stm32/)
(1) Hitachi/Renesas SH-1 (arch/sh/src/sh1)
(11) z80/z8/ez80/z180 (arch/z80/)
(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.
Title: pause() NON-COMPLIANCE
Description: In the POSIX description of this function is the pause() function
will 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
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.
Title: INCOMPATIBILITES WITH execv() AND execl()
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
patacongo
committed
Title: ISSUES WITH atexit() AND on_exit()
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?
The fix for all of these issues it to have the callbacks
run on the caller's thread (as with signal handlers).
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: REMOVE TASK_DELETE
Description: Need to remove or fix task delete. This interface is non-
standard and not safe. Arbitrary deleting tasks can cause
serious problems such as memory leaks. Better to remove it
than to retain it as a latent bug.
Currently used within the OS and also part of the
implementation of pthread_cancel() and task_restart() (which
should also go for the same reasons). It is used in
NxWM::CNxConsole to terminate console tasks and also in
apps/netutils/thttpd to kill CGI tasks that timeout.
Status: Open
Priority: Low and not easily removable.
Title: FREE MEMORY ON TASK EXIT
Description: Add an option to free all memory allocated by a task when the
task exits. This is probably not be worth the overhead for a
deeply embedded system.
There would be complexities with this implementation as well
because often one task allocates memory and then passes the
memory to another: The task that "owns" the memory may not
be the same as the task that allocated the memory.
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
Update. From the NuttX forum:
...there is a good reason why task A should never delete task B.
That is because you will strand memory resources. Another feature
lacking in most flat address space RTOSs is automatic memory
clean-up when a task exits.
That behavior just comes for free in a process-based OS like Linux:
Each process has its own heap and when you tear down the process
environment, you naturally destroy the heap too.
But RTOSs have only a single, shared heap. I have spent some time
thinking about how you could clean up memory required by a task
when a task exits. It is not so simple. It is not as simple as
just keeping memory allocated by a thread in a list then freeing
the list of allocations when the task exists.
It is not that simple because you don't know how the memory is
being used. For example, if task A allocates memory that is used
by task B, then when task A exits, you would not want to free that
memory needed by task B. In a process-based system, you would
have to explicitly map shared memory (with reference counting) in
order to share memory. So the life of shared memory in that
environment is easily managed.
I have thought that the way that this could be solved in NuttX
would be: (1) add links and reference counts to all memory allocated
by a thread. This would increase the memory allocation overhead!
(2) Keep the list head in the TCB, and (3) extend mmap() and munmap()
to include the shared memory operations (which would only manage
the reference counting and the life of the allocation).
Then what about pthreads? Memory should not be freed until the last
pthread in the group exists. That could be done with an additional
reference count on the whole allocated memory list (just as streams
and file descriptors are now shared and persist until the last
pthread exits).
I think that would work but to me is very unattractive and
inconsistent with the NuttX "small footprint" objective. ...
Other issues:
- Memory free time would go up because you would have to remove
the memory from that list in free().
- There are special cases inside the RTOS itself. For example,
if task A creates task B, then initial memory allocations for
task B are created by task A. Some special allocators would
be required to keep this memory on the correct list (or on
no list at all).
Priority: Medium/Low, a good feature to prevent memory leaks but would
have negative impact on memory usage and code size.
o Signals (sched/, arch/)
^^^^^^^^^^^^^^^^^^^^^^^
Description: 'Standard' signals and signal actions are not supported.
(e.g., SIGINT, SIGSEGV, etc).
Priority: Low, required by standards but not so critical for an
embedded system.
Description: sig_notify() logic does not support SIGEV_THREAD; structure
struct sigevent does not provide required members sigev_notify_function
or sigev_notify_attributes.
Status: Low, there are alternative designs. However, these features
are required by the POSIX standard.
Priority: Low for now
Title: SIGNAL NUMBERING
Description: In signal.h, the range of valid signals is listed as 0-31. However,
in many interfaces, 0 is not a valid signal number. The valid
signal number should be 1-32. The signal set operations would need
to map bits appropriately.
Status: Open
Priority: Low. Even if there are only 31 usable signals, that is still a lot.
Description: pthread_cancel(): Should implement cancellation points and
pthread_testcancel()
patacongo
committed
Title: PTHREAD_PRIO_PROTECT
Description: Extended pthread_mutexattr_setprotocol() suport PTHREAD_PRIO_PROTECT:
patacongo
committed
"When a thread owns one or more mutexes initialized with the
PTHREAD_PRIO_PROTECT protocol, it shall execute at the higher of its
priority or the highest of the priority ceilings of all the mutexes
owned by this thread and initialized with this attribute, regardless of
whether other threads are blocked on any of these mutexes or not.
"While a thread is holding a mutex which has been initialized with
the PTHREAD_PRIO_INHERIT or PTHREAD_PRIO_PROTECT protocol attributes,
it shall not be subject to being moved to the tail of the scheduling queue
at its priority in the event that its original priority is changed,
such as by a call to sched_setparam(). Likewise, when a thread unlocks
a mutex that has been initialized with the PTHREAD_PRIO_INHERIT or
PTHREAD_PRIO_PROTECT protocol attributes, it shall not be subject to
being moved to the tail of the scheduling queue at its priority in the
event that its original priority is changed."
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
Priority: Low -- about zero, probably not that useful. Priority inheritance is
already supported and is a much better solution. And it turns out
that priority protection is just about as complex as priority inheritance.
Exerpted from my post in a Linked-In discussion:
"I started to implement this HLS/"PCP" semaphore in an RTOS that I
work with (http://www.nuttx.org) and I discovered after doing the
analysis and basic code framework that a complete solution for the
case of a counting semaphore is still quite complex -- essentially
as complex as is priority inheritance.
"For example, suppose that a thread takes 3 different HLS semaphores
A, B, and C. Suppose that they are prioritized in that order with
A the lowest and C the highest. Suppose the thread takes 5 counts
from A, 3 counts from B, and 2 counts from C. What priority should
it run at? It would have to run at the priority of the highest
priority semaphore C. This means that the RTOS must maintain
internal information of the priority of every semaphore held by
the thread.
"Now suppose it releases one count on semaphore B. How does the
RTOS know that it still holds 2 counts on B? With some complex
internal data structure. The RTOS would have to maintain internal
information about how many counts from each semaphore are held
by each thread.
"How does the RTOS know that it should not decrement the priority
from the priority of C? Again, only with internal complexity. It
would have to know the priority of every semaphore held by
every thread.
"Providing the HLS capability on a simple pthread mutex would not
be such quite such a complex job if you allow only one mutex per
thread. However, the more general case seems almost as complex
as priority inheritance. I decided that the implementation does
not have value to me. I only wanted it for its reduced
complexity; in all other ways I believe that it is the inferior
solution. So I discarded a few hours of programming. Not a
big loss from the experience I gained."
patacongo
committed
o Kernel/Protected Build
^^^^^^^^^^^^^^^^^^^^^^
Gregory Nutt
committed
Title: NSH PARTITIONING.
Description: There are issues with several NSH commands in the NuttX kernel
and protected build modes (where NuttX is built as a monolithic
kernel and user code must trap into the protected kernel via
syscalls). The current NSH implementation has several commands
that call directly into kernel internal functions for which
there is no syscall available. The commands cause link failures
in the kernel/protected build mode and must currently be disabled.
Gregory Nutt
committed
Here are known problems that must be fixed:
COMMAND KERNEL INTERFACE(s)
-------- ----------------------------------------------
losetup losetup(), loteardown()
Gregory Nutt
committed
mkfatfs mkfatfs
mkrd ramdisk_register()
dd bchlib_setup(), bchlib_read(), bchlib_write(),
bchlib_teardown()
ps sched_foreach()
ifup netdev_foreach()
ifdown netdev_foreach()
Gregory Nutt
committed
ifconfig netdev_foreach(), g_netstats
Gregory Nutt
committed
Gregory Nutt
committed
Priority: Medium/High -- the kernel build configuration is not fully fielded
Gregory Nutt
committed
Title: NSH free COMMAND LIMITATION
Description: The NSH 'free' command only shows memory usage in the user
heap only, not usage in the kernel heap. I am thinking that
kernel heap memory usage should be available in /proc/memory.
Status: Open
Priority: Medium/High
Gregory Nutt
committed
Title: TELNETD PARTITIONING.
Description: Telnetd is implemented as a driver that resides in the apps/
directory. In the kernel/protected build modes, the driver
logic must be moved into the kernel part of the build (nuttx/,
although the application level interfaces must stay in apps/).
Gregory Nutt
committed
Status: Open
Priority: Medium
Title: NxTERM PARTITIONING.
Description: NxTerm is implemented (correctly) as a driver that resides
Gregory Nutt
committed
in the nuttx/ directory. However, the user interfaces must be
moved into a NuttX library or into apps/. Currently
applications calls to the NxTerm user interfaces are
Gregory Nutt
committed
undefined.
Gregory Nutt
committed
Priority: Medium
Title: C++ CONSTRUCTORS HAVE TOO MANY PRIVILEGES (PROTECTED MODE)
Description: When a C++ ELF module is loaded, its C++ constructors are called
via sched/task_starthook.c logic. This logic runs in protected mode.
The is a security hole because the user code runs with kernel-
Gregory Nutt
committed
privileges when the constructor executes.
Destructors likely have the opposite problem. The probably try to
execute some kernel logic in user mode? Obviously this needs to
be investigated further.
Status: Open
Priority: Low (unless you need build a secure C++ system).
Title: TOO MANY SYSCALLS
Description: There are a few syscalls that operate very often in user space.
Since syscalls are (relatively) time consuming this could be
a performance issue. Here is some numbers that I collected
sem_post - 18% of syscalls
sem_wait - 18% of syscalls
getpid - 59% of syscalls
--------------------------
95% of syscalls
Obviously system performance could be improved greatly by simply
optimizing these functions so that they do not need to system calls
so frequently. getpid() is (I believe) part of the re-entrant
semaphore logic. Something like TLS might be used to retain the
thread's ID locally.
Linux, for example, has functions call up() and down(). up()
increments the semaphore count but does not call into the kernel
unless incrementing the count unblocks a task; similarly, down
decrements the count and does not call into the kernel unless
the count becomes negative the caller must be blocked.
"I am thinking that there should be a "magic" global, user-accessible
variable that holds the PID of the currently executing thread;
basically the PID of the task at the head of the ready-to-run list.
This variable would have to be reset each time the head of the ready-
to-run list changes.
"Then getpid() could be implemented in user space with no system call
by simply reading this variable.
"This one would be easy: Just a change to include/nuttx/userspace.h,
configs/*/kernel/up_userspace.c, libc/, sched/sched_addreadytorun.c, and
sched/sched_removereadytorun.c. That would eliminate 59% of the syscalls."
Update:
This is probably also just a symptom of the OS test that does mostly
console output. The requests for the pid() are part of the
implementation of the I/O's re-entrant semaphore implementation and
would not be an issue in the more general case.
Status: Open
Priority: Low-Medium. Right now, I do not know if these syscalls are a
real performance issue or not. The above statistics were collected
from a an atypical application (the OS test), and does an excessive
amount of console output. There is probably no issue with more typical
embedded applications.
Title: SECURITY ISSUES
Description: In the current designed, the kernel code calls into the user-space
allocators to allocate user-space memory. It is a security risk to
call into user-space in kernel-mode because that could be exploited
to gain control of the system. That could be fixed by dropping to
user mode before trapping into the memory allocators; the memory
allocators would then need to trap in order to return (this is
already done to return from signal handlers; that logic could be
renamed more generally and just used for a generic return trap).
Another place where the system calls into the user code in kernel
mode is work_usrstart() to start the user work queue. That is
another security hole that should be plugged.
Status: Open
Priority: Low (unless security becomes an issue).
Title: MICRO-KERNEL
Description: The initial kernel build cut many interfaces at a very high level.
Gregory Nutt
committed
The resulting monolithic kernel is then rather large. It would
not be a prohibitively large task to reorganize the interfaces so
that NuttX is built as a micro-kernel, i.e., with only the core
OS services within the kernel and with other OS facilities, such
Gregory Nutt
committed
as the file system, message queues, etc., residing in user-space
and to interfacing with those core OS facilities through traps.
Status: Open
Priority: Low. This is a good idea and certainly an architectural
improvement. However, there is no strong motivation now do
do that partitioning work.
Title: USE OF SIZE_T IN NEW OPERATOR
Description: The argument of the 'new' operators should take a type of
size_t (see libxx/libxx_new.cxx and libxx/libxx_newa.cxx). But
size_t has an unknown underlying. In the nuttx sys/types.h
header file, size_t is typed as uint32_t (which is determined by
architecture-specific logic). But the C++ compiler may believe
that size_t is of a different type resulting in compilation errors
in the operator. Using the underlying integer type Instead of
size_t seems to resolve the compilation issues.
Status: Kind of open. There is a workaround. Setting CONFIG_CXX_NEWLONG=y
will define the operators with argument of type unsigned long;
Setting CONFIG_CXX_NEWLONG=n will define the operators with argument
of type unsigned int. But this is pretty ugly! A better solution
would be to get a hold of the compilers definition of size_t.
Update: Static constructors are implemented for the STM32 F4 and
this will provide the model for all solutions. Basically, if
CONFIG_HAVE_CXXINITIALIZE=y is defined in the configuration, then
board-specific code must provide the interface up_cxxinitialize().
up_cxxinitialize() is called from application logic to initialize
all static class instances. This TODO item probably has to stay
open because this solution is only available on STM32 F4.
Status: Open
Priority: Low, depends on toolchain. Call to gcc's built-in static
constructor logic will probably have to be performed by
Gregory Nutt
committed
user logic in the application.
Gregory Nutt
committed
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
Title: STATIC CONSTRUCTORS AND MULTITASKING
Description: The logic that calls static constructors operates on the main
thread of the initial user application task. Any static
constructors that cache task/thread specific information such
as C streams or file descriptors will not work in other tasks.
See also UCLIBC++ AND STATIC CONSTRUCTORS below.
Status: Open
Priority: Low and probably will not changed. In these case, there will
need to be an application specific solution.
Title: UCLIBC++ AND STATIC CONSTRUCTORS
uClibc++ was designed to work in a Unix environment with
processes and with separately linked executables. Each process
has its own, separate uClibc++ state. uClibc++ would be
instantiated like this in Linux:
1) When the program is built, a tiny start-up function is
included at the beginning of the program. Each program has
its own, separate list of C++ constructors.
2) When the program is loaded into memory, space is set aside
for uClibc's static objects and then this special start-up
routine is called. It initializes the C library, calls all
of the constructors, and calls atexit() so that the destructors
will be called when the process exits.
In this way, you get a per-process uClibc++ state since there
is per-process storage of uClibc++ global state and per-process
initialization of uClibc++ state.
Compare this to how NuttX (and most embedded RTOSs) would work:
1) The entire FLASH image is built as one big blob. All of the
constructors are lumped together and all called together at
one time.
This, of course, does not have to be so. We could segregate
constructors by some criteria and we could use a task start
up routine to call constructors separately. We could even
use ELF executables that are separately linked and already
have their constructors separately called when the ELF
executable starts.
But this would not do you very much good in the case of
uClibc++ because:
2) NuttX does not support processes, i.e., separate address
environments for each task. As a result, the scope of global
data is all tasks. Any change to the global state made by
one task can effect another task. There can only one
uClibc++ state and it will be shared by all tasks. uClibc++
apparently relies on global instances (at least for cin and
cout) there is no way to to have any unique state for any
"task group".
[NuttX does not support processes because in order to have
true processes, your hardware must support a memory management
unit (MMU) and I am not aware of any mainstream MCU that has
an MMU (or, at least an MMU that is capable enough to support
processes).]
NuttX does not have processes, but it does have "task groups".
See http://www.nuttx.org/doku.php?id=wiki:nxinternal:tasksnthreads.
A task group is the task plus all of the pthreads created by
the task via pthread_create(). Resources like FILE streams
are shared within a task group. Task groups are like a poor
man's process.
This means that if the uClibc++ static classes are initialized
by one member of a task group, then cin/cout should work
correctly with all threads that are members of task group. The
destructors would be called when the final member of the task
group exists (if registered via atexit()).
So if you use only pthreads, uClibc++ should work very much like
it does in Linux. If your NuttX usage model is like one process
with many threads then you have Linux compatibility.
If you wanted to have uClibc++ work across task groups, then
uClibc++ and NuttX would need some extensions. I am thinking
along the lines of the following:
1) There is a per-task group storage are within the RTOS (see
include/nuttx/sched.h). If we add some new, non-standard APIs
Gregory Nutt
committed
then uClibc++ could get access to per-task group storage (in
the spirit of pthread_getspecific() which gives you access to
per-thread storage).
2) Then move all of uClibc++'s global state into per-task group
storage and add a uClibc++ initialization function that would:
a) allocate per-task group storage, b) call all of the static
constructors, and c) register with atexit() to perform clean-
up when the task group exits.
That would be a fair amount of effort. I don't really know what
the scope of such an effort would be. I suspect that it is not
large but probably complex.
NOTES:
1) See STATIC CONSTRUCTORS AND MULTITASKING
2) To my knowledge, only some uClibc++ ofstream logic is
sensitive to this. All other statically initialized classes
seem to work OK across different task groups.
Status: Open
Priority: Low. I have no plan to change this logic now unless there is
some strong demand to do so.
Description: Not all of the NXFLAT test under apps/examples/nxflat are working.
Most simply do not compile yet. tests/mutex runs okay but
outputs garbage on completion.
patacongo
committed
Update: 13-27-1, tests/mutex crashed with a memory corruption
problem the last time that I ran it.
Description: The ARM up_getpicbase() does not seem to work. This means
the some features like wdog's might not work in NXFLAT modules.
Status: Open
Priority: Medium-High
Description: At present, all .rodata must be put into RAM. There is a
tentative design change that might allow .rodata to be placed
in FLASH (see Documentation/NuttXNxFlat.html).
Status: Open
Priority: Medium
Title: GOT-RELATIVE FUNCTION POINTERS
Description: If the function pointer to a statically defined function is
taken, then GCC generates a relocation that cannot be handled
by NXFLAT. There is a solution described in Documentation/NuttXNxFlat.html,
by that would require a compiler change (which we want to avoid).
The simple workaround is to make such functions global in scope.
Status: Open
Priority: Low (probably will not fix)
Title: USE A HASH INSTEAD OF A STRING IN SYMBOL TABLES
Description: In the NXFLAT symbol tables... Using a 32-bit hash value instead
of a string to identify a symbol should result in a smaller footprint.
Status: Open
Priority: Low
Title: WINDOWS-BASED TOOLCHAIN BUILD
Description: Windows build issue. Some of the configurations that use NXFLAT have
NXFLATLDFLAGS2 = $(NXFLATLDFLAGS1) -T$(TOPDIR)/binfmt/libnxflat/gnu-nxflat-gotoff.ld -no-check-sections
That will not work for windows-based tools because they require Windows
style paths. The solution is to do something like this:
if ($(WINTOOL)y)
NXFLATLDSCRIPT=${cygpath -w $(TOPDIR)/binfmt/libnxflat/gnu-nxflat-gotoff.ld}
NXFLATLDSCRIPT=$(TOPDIR)/binfmt/libnxflat/gnu-nxflat-gotoff.ld
NXFLATLDFLAGS2 = $(NXFLATLDFLAGS1) -T"$(NXFLATLDSCRIPT)" -no-check-sections
Status: Open
Priority: There are too many references like the above. They will have
to get fixed as needed for Windows native tool builds.
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
Title: TOOLCHAIN COMPATIBILITY PROBLEM
Descripton: The older 4.3.3 compiler generates GOTOFF relocations to the constant
strings, like:
.L3:
.word .LC0(GOTOFF)
.word .LC1(GOTOFF)
.word .LC2(GOTOFF)
.word .LC3(GOTOFF)
.word .LC4(GOTOFF)
Where .LC0, LC1, LC2, LC3, and .LC4 are the labels correponding to strings in
the .rodata.str1.1 section. One consequence of this is that .rodata must reside
in D-Space since it will addressed relative to the GOT (see the section entitled
"Read-Only Data in RAM" at
http://nuttx.org/Documentation/NuttXNxFlat.html#limitations).
The newer 4.6.3compiler generated PC relative relocations to the strings:
.L2:
.word .LC0-(.LPIC0+4)
.word .LC1-(.LPIC1+4)
.word .LC2-(.LPIC2+4)
.word .LC3-(.LPIC4+4)
.word .LC4-(.LPIC5+4)
This is good and bad. This is good because it means that .rodata.str1.1 can now
reside in FLASH with .text and can be accessed using PC-relative addressing.
That can be accomplished by simply moving the .rodata from the .data section to
the .text section in the linker script. (The NXFLAT linker script is located at
nuttx/binfmt/libnxflat/gnu-nxflat.ld).
This is bad because a lot of stuff may get broken an a lot of test will need to
be done. One question that I have is does this apply to all kinds of .rodata?
Or just to .rodata.str1.1?
Status: Open. Many of the required changes are in place but, unfortunately, not enough
go be fully functional. I think all of the I-Space-to-I-Space fixes are in place.
However, the generated code also includes PC-relative references to .bss which
just cannot be done.
Priority: Medium. The workaround for now is to use the older, 4.3.3 OABI compiler.
Description: IPv6 support is incomplete. Adam Dunkels has recently announced
IPv6 support for uIP (currently only as part of Contiki). Those
changes need to be ported to NuttX.
Status: Open. No work will probably be done until there is a specific
requirement for IPv6.
Title: LISTENING FOR UDP BROADCASTS
Description: Incoming UDP broadcast should only be accepted if listening on
INADDR_ANY(?)
Status: Open
Priority: Low
Title: STANDARDIZE ETHERNET DRIVER STATISTICS
Description: Need to standardize collection of statistics from network
drivers. apps/nshlib ifconfig command should present
Priority: Low. This is not a bug but an enhancement idea.
Title: CONCURRENT TCP SEND OPERATIONS
Description: At present, there cannot be two concurrent active TCP send
operations in progress using the same socket. This is because
the uIP ACK logic will support only one transfer at a time. The
solution is simple: A mutex will be needed to make sure that each
send that is started is able to be the exclusive sender until all of
the data to be sent has been ACKed.
Status: Open. There is some temporary logic to apps/nshlib that does
this same fix and that temporary logic should be removed when
send() is fixed.
Priority: Medium-Low. This is an important issue for applications that
send on the same TCP socket from multiple threads.
Description: TCP supports read-ahead buffering to handle the receipt of
TCP/IP packets when there is no read() in place. Should such
capability be useful for UDP? PRO: Would reduce packet loss
and enable support for poll()/select(). CON: UDP is inherently
lossy so why waste memory footprint?
Status: Open
Priority: Medium
Title: NO POLL/SELECT ON UDP SOCKETS
Description: poll()/select() is not implemented for UDP sockets because they do
do not support read-ahead buffering. Therefore, there is never
a case where you can read from a UDP socket without blocking.
Status: Open, depends on UDP read-ahead support
Priority: Medium
Title: POLL/SELECT ON TCP SOCKETS NEEDS READ-AHEAD
Description: poll()/select() only works for availability of buffered TCP
read data (when read-ahead is enabled). The way writing is
handled in uIP, all sockets must wait when send and cannot
Status: Open, probably will not be fixed.
Priority: Medium... this does effect porting of applications that expect
different behavior from poll()/select()
Title: SOCKETS DO NOT ALWAYS SUPPORT O_NONBLOCK
Description: sockets do not support all modes for O_NONBLOCK. Sockets
support only (1) TCP/IP non-blocking read operations when read-ahead
buffering is enabled, and (2) TCP/IP accept() operations when TCP/IP
connection backlog is enabled.
Status: Open
Priority: Low.
Title: UNFINISHED CRYSTALLAN CS89X0 DRIVER
Description: I started coding a CrystalLan CS89x0 driver (drivers/net/cs89x0.c),
but never finished it.
Status: Open
Priority: Low unless you need it.
Title: INTERFACES TO LEAVE/JOIN IGMP MULTICAST GROUP
Description: The interfaces used to leave/join IGMP multicast groups is non-standard.
RFC3678 (IGMPv3) suggests ioctl() commands to do this (SIOCSIPMSFILTER) but
also status that those APIs are historic. NuttX implements these ioctl
commands, but is non-standard because: (1) It does not support IGMPv3, and
(2) it looks up drivers by their device name (eg., "eth0") vs IP address.
Linux uses setsockopt() to control multicast group membership using the
IP_ADD_MEMBERSHIP and IP_DROP_MEMBERSHIP options. It also looks up drivers
using IP addresses (It would require additional logic in NuttX to look up
drivers by IP address). See http://tldp.org/HOWTO/Multicast-HOWTO-6.html
Status: Open
Priority: Medium. All standards compatibility is important to NuttX. However, most
the mechanism for leaving and joining groups is hidden behind a wrapper
function so that little of this incompatibilities need be exposed.
Title: CLOSED CONNECTIONS IN THE BACKLOG
If a connection is backlogged but accept() is not called quickly, then
that connection may time out. How should this be handled? Should the
connection be removed from the backlog if it is times out or is closed?
Or should it remain in the backlog with a status indication so that accept()
can fail when it encounteres the invalid connection?
Gregory Nutt
committed
Priority: Medium. Important on slow applications that will not accept
connections promptly.
Title: PER DEVICE PORT NUMBERS
Description: TCP and UDP ports numbers are assigned as separater but global resources.
Separate meaning that a UDP and TCP socket with the same port number are
distinct. But global in the since that each TCP port number must be unique
and TCP sockets. UDP port numbers must be similarly unique.
This causes prorblems for the case where there multiple network devices
configured into the system. In that case, it should be possible to assign
the same TCP (or UDP) port number if the connection is associated with
different network devices. For example, if there are two instances of
a webserver, each listening for connections on a different device, each
should be able to use port 80 to listen for connections.
The solution is is move the TCP and UDP port related resources: They
should not be global but shoud, instead, by a part of the device structure,
struct net_drivers_s.
Status: Open
Priority: Very low if you have only a single network interface. Higher if you
have more than one. Very high if you need to have the same port numbers
on each network served by the device.
Title: INTERRUPT LEVEL PROCESSING IN ETHERNET DRIVERS
Description: Too many Ethernet drivers do interrupt-level processing with the network
stack. The network stack supports either interrupt level processing or
normal task level processing (depending on CONFIG_NET_NOINTS). This is
really a very bad use of CPU resources; All of the network stack processing
should be more to a work queue (and, all use of CONFIG_NET_NOINTS=n should
be eliminated).
Status: Open
Priority: Pretty high if you want a well behaved system.
o USB (drivers/usbdev, drivers/usbhost)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Title: USB STORAGE DRIVER DELAYS
Description: There is a workaround for a bug in drivers/usbdev/usbdev_storage.c.
that involves delays. This needs to be redesigned to eliminate these
delays. See logic conditioned on CONFIG_USBMSC_RACEWAR.
Gregory Nutt
committed
If queuing of stall requests is supported by DCD then this workaround
is not required. In this case, (1) the stall is not sent until all
write requests preceding the stall request are sent, (2) the stall is
sent, and then after the stall is cleared, (3) all write requests
queued after the stall are sent.
See, for example, the queuing of pending stall requests in the SAM3/4
UDP driver at arch/arm/src/sam34/sam_udp.c. There the logic is do this
is implemented with a normal request queue, a pending request queue, a
stall flag and a stall pending flag:
1) If the normal request queue is not empty when the STALL request is
received, the stall pending flag is set.
2) If addition write requests are received while the stall pending flag
is set (or while waiting for the stall to be sent), those write requests
go into the pending queue.
3) When the normal request queue empties successful and all of the write
transfers complete, the STALL is sent. The stall pending flag is
cleared and the stall flag is set. Now the endpoint is really stalled.
4) After the STALL is cleared (via the Clear Feature SETUP), the pending
request queue is copied to the normal request queue, the stall flag is
cleared, and normal write request processing resumes.
Title: RTL8187 DRIVER IS UNFINISHED
Description: misc/drivers/usbhost_rtl8187.c is a work in progress. There is no RTL8187
driver available yet. That is a work in progress it was abandoned because
it depends on having an 802.11g stack.
Status: Open
Priority: Low (Unless you need RTL8187 support).
Title: EP0 OUT CLASS DATA
Description: There is no mechanism in place to handle EP0 OUT data transfers.
There are two aspects to this problem, neither are easy to fix
(only because of the number of drivers that would be impacted):
1. The class drivers only send EP0 write requests and these are
only queued on EP0 IN by this drivers. There is never a read
request queued on EP0 OUT.
2. But EP0 OUT data could be buffered in a buffer in the driver
data structure. However, there is no method currently
defined in the USB device interface to obtain the EP0 data.
Updates: (1) The USB device-to-class interface as been extended so
that EP0 OUT data can accompany the SETUP request sent to the
class drivers. (2) The logic in the STM32 F4 OTG FS device driver
has been extended to provide this data. Updates are still needed
to other drivers.
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
Here is an overview of the required changes:
New two buffers in driver structure:
1. The existing EP0 setup request buffer (ctrlreq, 8 bytes)
2. A new EP0 data buffer to driver state structure (ep0data,
max packetsize)
Add a new state:
3. Waiting for EP0 setup OUT data (EP0STATE_SETUP_OUT)
General logic flow:
1. When an EP0 SETUP packet is received:
- Read the request into EP0 setup request buffer (ctrlreq,
8 bytes)
- If this is an OUT request with data length, set the EP0
state to EP0STATE_SETUP_OUT and wait to receive data on
EP0.
- Otherwise, the SETUP request may be processed now (or,
in the case of the F4 driver, at the conclusion of the
SETUP phase).
2. When EP0 the EP0 OUT DATA packet is received:
- Verify state is EP0STATE_SETUP_OUT
- Read the request into the EP0 data buffer (ep0data, max
packet size)
- Now process the previously buffered SETUP request along
with the OUT data.
3. When the setup packet is dispatched to the class driver,
the OUT data must be passed as the final parameter in the
call.
Update 2013-9-2: The new USB device-side driver for the SAMA5D3
correctly supports OUT SETUP data following the same design as
per above.
Update 2013-11-7: David Sidrane has fixed with issue with the
STM32 F1 USB device driver. Still a few more to go before this
can be closed out.
Status: Open
Priority: High for class drivers that need EP0 data. For example, the
CDC/ACM serial driver might need the line coding data (that
Title: USB HUB SUPPORT
Description: Add support for USB hubs
Status: Open
Priority: Low/Unknown. This is a feature enhancement.
patacongo
committed
o Libraries (libc/)
^^^^^^^^^^^^^^^^^
Title: SIGNED time_t
Description: The NuttX time_t is type uint32_t. I think this is consistent
with all standards and with normal usage of time_t. However,
according to Wikipedia, time_t is usually implemented as a
signed 32-bit value.
Status: Open
Priority: Very low unless there is some compelling issue that I do not
know about.
Description: The definition of environ in stdlib.h is bogus and will not
work as it should. This is because the underlying
representation of the environment is not an arry of pointers.
Status: Open
Description: Need some minimal termios support... at a minimum, enough to
switch between raw and "normal" modes to support behavior like
that needed for readline().
patacongo
committed
UPDATE: There is growing functionality in libc/termios/ and in the
patacongo
committed
ioctl methods of several MCU serial drivers (stm32, lpc43, lpc17,
pic32). However, as phrased, this bug cannot yet be closed since
this "growing functionality" does not address all termios.h
functionality and not all serial drivers support termios.