Squashed commit of the following:
configs/: The few configurations that formerly set CONFIG_NFILE_DESCRIPTORS=0 should not default, rather they should set the number of descriptors to 3.
fs/: Remove all conditional logic based on CONFIG_NFILE_DESCRIPTORS == 0
tools/: Tools updates for changes to usage of CONFIG_NFILE_DESCRIPTORS.
syscall/: Remove all conditional logic based on CONFIG_NFILE_DESCRIPTORS == 0
libs/: Remove all conditional logic based on CONFIG_NFILE_DESCRIPTORS == 0
include/: Remove all conditional logic based on CONFIG_NFILE_DESCRIPTORS == 0
drivers/: Remove all conditional logic based on CONFIG_NFILE_DESCRIPTORS == 0
Documentation/: Remove all references to CONFIG_NFILE_DESCRIPTORS == 0
binfmt/: Remove all conditional logic based on CONFIG_NFILE_DESCRIPTORS == 0
arch/: Remove all conditional logic based on CONFIG_NFILE_DESCRIPTORS == 0
net/: Remove all conditional logic based on CONFIG_NFILE_DESCRIPTORS == 0
sched/: Remove all conditional logic based on CONFIG_NFILE_DESCRIPTORS == 0
sched/Kconfig: CONFIG_NFILE_DESCRIPTORS may no longer to set to a value less than 3
configs/: Remove all settings for CONFIG_NFILE_DESCRIPTORS < 3
sched/init/nx_bringup.c: Fix a naming collision.
sched/init: Rename os_start() to nx_start()
sched/init: Rename os_smp* to nx_smp*
sched/init: Rename os_bringup to nx_bringup
sched/init: rename all internal static functions to begin with nx_ vs os_
Squashed commit of the following:
Trivial, cosmetic
sched/, arch/, and include: Rename task_vforkstart() as nxtask_vforkstart()
sched/, arch/, and include: Rename task_vforkabort() as nxtask_vforkabort()
sched/, arch/, and include: Rename task_vforksetup() as nxtask_vfork_setup()
sched/: Rename notify_cancellation() as nxnotify_cancellation()
sched/: Rename task_recover() to nxtask_recover()
sched/task, sched/pthread/, Documentation/: Rename task_argsetup() and task_terminate() to nxtask_argsetup() and nxtask_terminate(), respectively.
sched/task: Rename task_schedsetup() to nxtask_schedsetup()
sched/ (plus some binfmt/, include/, and arch/): Rename task_start() and task_starthook() to nxtask_start() and nxtask_starthook().
arch/ and sched/: Rename task_exit() and task_exithook() to nxtask_exit() and nxtask_exithook(), respectively.
sched/task: Rename all internal, static, functions to begin with the nx prefix.
Signal handlers maybe run with interrupts enabled or disabled, depending on how the task the received the signal was blocked. (i.e.: If sem_wait() is called, then we disable interrupts, then block the currently running task). This could be dangerous, because user code would be running with interrupts disabled.
This change forces interrupts to be enabled in up_sigdeliver() before executing the signal handler calling up_irq_enable() explicitly. This is safe because, when we return to normal execution, interrupts will be restored to their previous state when the signal handler returns.
This commit backs out most of commit b4747286b1. That change was added because sem_wait() would sometimes cause cancellation points inappropriated. But with these recent changes, nxsem_wait() is used instead and it is not a cancellation point.
In the OS, all calls to sem_wait() changed to nxsem_wait(). nxsem_wait() does not return errors via errno so each place where nxsem_wait() is now called must not examine the errno variable.
In all OS functions (not libraries), change sem_wait() to nxsem_wait(). This will prevent the OS from creating bogus cancellation points and from modifying the per-task errno variable.
sched/semaphore: Add the function nxsem_wait(). This is a new internal OS interface. It is functionally equivalent to sem_wait() except that (1) it is not a cancellation point, and (2) it does not set the per-thread errno value on return.
sched/semaphore: Add nxsem_post() which is identical to sem_post() except that it never modifies the errno variable. Changed all references to sem_post in the OS to nxsem_post().
sched/semaphore: Add nxsem_destroy() which is identical to sem_destroy() except that it never modifies the errno variable. Changed all references to sem_destroy() in the OS to nxsem_destroy().
libc/semaphore and sched/semaphore: Add nxsem_getprotocol() and nxsem_setprotocola which are identical to sem_getprotocol() and set_setprotocol() except that they never modifies the errno variable. Changed all references to sem_setprotocol in the OS to nxsem_setprotocol(). sem_getprotocol() was not used in the OS
libc/semaphore: Add nxsem_getvalue() which is identical to sem_getvalue() except that it never modifies the errno variable. Changed all references to sem_getvalue in the OS to nxsem_getvalue().
sched/semaphore: Rename all internal private functions from sem_xyz to nxsem_xyz. The sem_ prefix is (will be) reserved only for the application semaphore interfaces.
libc/semaphore: Add nxsem_init() which is identical to sem_init() except that it never modifies the errno variable. Changed all references to sem_init in the OS to nxsem_init().
sched/semaphore: Rename sem_tickwait() to nxsem_tickwait() so that it is clear this is an internal OS function.
sched/semaphoate: Rename sem_reset() to nxsem_reset() so that it is clear this is an internal OS function.
Provide a user defined callback context for irq's, such that when
registering a callback users can provide a pointer that will get
passed back when the isr is called.
Atmel's AVR8 toolchain is similar to WinAVR, but at present moment
it has one important feature that WinAVR does not. The __flash and __memx
allow built in comiler support for transparent program memory pointers.
Functions that use such pointers will work both with RAM arrays and
flash memory arrays. The compiler generates an appropriate code automatically.
For systems with tiny memory like atmega, this is very important and
allows to move all static const strings into flash.
The main challenge is to change the context switch code to be aware of the
extra byte that is saved on stack during call and intterupt. This relates also
to the task startup and signal handling.
For AVR chips (Atmega2560) Program Counter register larger than 16 bits
EIND represents the most significant byte that is used for EICALL and EIJMP
instructions.
Setting of EIND is normally managed by compiler, but I have seen a situation
when for first 64K flash segment compiler didn't set EINT explicitly. Thus
setting EIND at system startup makes sure we are safe.
Disabling interrupts at the very beginning of system init does not
make sense after reset since interrupts are disabled anyway. But
it is very convenient for debugging purposes, in situations when the
system misbehaves and ocassionally jumps to zero.
Minor bug while working on Arduino Mega support. I didn't add support
for ARCH_HAVE_LEDS and have it undefined in .config. To my surprise compilation
failed since AVR code had a related function compiled in.
This is for forthcoming Atmega2560 support. The Atmega2560 has 24-bit PC
thus, PCH and PCL would become PCH, PCM and PCL (M for Middle). The problem
that in this notation PCM is equivalent to former PCH. This makes compatable
porting kind of difficult, at least for my taste.
Instead PCH becomes PC0 and PCL becomes PC1 (think of the index as order of
bytes pushed to stack when call is performed, PC0 as MSB goes first, PC1
goes to stack second, and for 24-bit PC, PC2 as LDB goes last).
Modify Kconfig to be aware of the new chip.
Add all the interrupt hanler constants and vectors where needed.
Move contsatnts from generic to specific headers when needed.
TCB_RESTORE macro has a problem when restoring Status Register
and returning from the function (in up_fullcontextrestore()) as non-atomic action.
If there is some frequently occurring interrupt, chances are that we will
enter the interrupt handler just before ret is called.
The handler may cause a context switch which, when unrolled, will
execute up_fullcontextrestore() function that employs TCB_RESTORE.
It will be interrupted again just before return, leaving part of context
switch content un-popped again, etc... Thus, chances are that the stack will
eventually blow.
Note that this is not some edge condition fix. This bug was discovered when
testing AVR with UART configured to work on 115200 baud rate.
