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.
